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[openttd/fttd.git] / src / train_cmd.cpp

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file train_cmd.cpp Handling of trains. */

#include "stdafx.h"
#include "error.h"
#include "articulated_vehicles.h"
#include "command_func.h"
#include "pathfinder/yapf/yapf.hpp"
#include "news_func.h"
#include "company_func.h"
#include "newgrf_sound.h"
#include "newgrf_text.h"
#include "strings_func.h"
#include "viewport_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "ai/ai.hpp"
#include "game/game.hpp"
#include "newgrf_station.h"
#include "effectvehicle_func.h"
#include "network/network.h"
#include "spritecache.h"
#include "core/random_func.hpp"
#include "company_base.h"
#include "newgrf.h"
#include "order_backup.h"
#include "zoom_func.h"
#include "signalbuffer.h"
#include "station_func.h"
#include "newgrf_debug.h"
#include "date_func.h"

#include "table/strings.h"
#include "table/train_cmd.h"

static bool ChooseTrainTrack (Train *v, RailPathPos origin, const PathMPos<RailPathPos> &pos, bool force_res, Trackdir *best_trackdir = NULL);
static bool TryPathExtend (Train *v, const RailPathPos &origin, bool mark_as_stuck = false);
static bool TrainCheckIfLineEnds(Train *v, bool reverse = true);
static StationID TrainEnterTile(Train *v, TileIndex tile, int x, int y);
bool TrainController(Train *v, Vehicle *nomove, bool reverse = true); // Also used in vehicle_sl.cpp.
static TileIndex TrainApproachingCrossingTile(const Train *v);
static void CheckIfTrainNeedsService(Train *v);
static void CheckNextTrainTile(Train *v);

static const byte _vehicle_initial_x_fract[4] = {10, 8, 4,  8};
static const byte _vehicle_initial_y_fract[4] = { 8, 4, 8, 10};

template <>
bool IsValidImageIndex<VEH_TRAIN>(uint8 image_index)
{
        return image_index < lengthof(_engine_sprite_base);
}

/**
 * Return the cargo weight multiplier to use for a rail vehicle
 * @param cargo Cargo type to get multiplier for
 * @return Cargo weight multiplier
 */
byte FreightWagonMult(CargoID cargo)
{
        if (!CargoSpec::Get(cargo)->is_freight) return 1;
        return _settings_game.vehicle.freight_trains;
}

/** Checks if lengths of all rail vehicles are valid. If not, shows an error message. */
void CheckTrainsLengths()
{
        const Train *v;
        bool first = true;

        FOR_ALL_TRAINS(v) {
                if (v->First() == v && !(v->vehstatus & VS_CRASHED)) {
                        for (const Train *u = v, *w = v->Next(); w != NULL; u = w, w = w->Next()) {
                                if (u->trackdir != TRACKDIR_DEPOT) {
                                        if ((w->trackdir != TRACKDIR_DEPOT &&
                                                        max(abs(u->x_pos - w->x_pos), abs(u->y_pos - w->y_pos)) != u->CalcNextVehicleOffset()) ||
                                                        (w->trackdir == TRACKDIR_DEPOT && TicksToLeaveDepot(u) <= 0)) {
                                                SetDParam(0, v->index);
                                                SetDParam(1, v->owner);
                                                ShowErrorMessage(STR_BROKEN_VEHICLE_LENGTH, INVALID_STRING_ID, WL_CRITICAL);

                                                if (!_networking && first) {
                                                        first = false;
                                                        DoCommandP(0, PM_PAUSED_ERROR, 1, CMD_PAUSE);
                                                }
                                                /* Break so we warn only once for each train. */
                                                break;
                                        }
                                }
                        }
                }
        }
}

/**
 * Recalculates the cached stuff of a train. Should be called each time a vehicle is added
 * to/removed from the chain, and when the game is loaded.
 * Note: this needs to be called too for 'wagon chains' (in the depot, without an engine)
 * @param allowed_changes Stuff that is allowed to change.
 */
void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
{
        uint16 max_speed = UINT16_MAX;

        assert(this->IsFrontEngine() || this->IsFreeWagon());

        const RailVehicleInfo *rvi_v = RailVehInfo(this->engine_type);
        EngineID first_engine = this->IsFrontEngine() ? this->engine_type : INVALID_ENGINE;
        this->gcache.cached_total_length = 0;
        this->compatible_railtypes = RAILTYPES_NONE;

        bool train_can_tilt = true;

        for (Train *u = this; u != NULL; u = u->Next()) {
                const RailVehicleInfo *rvi_u = RailVehInfo(u->engine_type);

                /* Check the this->first cache. */
                assert(u->First() == this);

                /* update the 'first engine' */
                u->gcache.first_engine = this == u ? INVALID_ENGINE : first_engine;
                u->railtype = rvi_u->railtype;

                if (u->IsEngine()) first_engine = u->engine_type;

                /* Set user defined data to its default value */
                u->tcache.user_def_data = rvi_u->user_def_data;
                this->InvalidateNewGRFCache();
                u->InvalidateNewGRFCache();
        }

        for (Train *u = this; u != NULL; u = u->Next()) {
                /* Update user defined data (must be done before other properties) */
                u->tcache.user_def_data = GetVehicleProperty(u, PROP_TRAIN_USER_DATA, u->tcache.user_def_data);
                this->InvalidateNewGRFCache();
                u->InvalidateNewGRFCache();
        }

        for (Train *u = this; u != NULL; u = u->Next()) {
                const Engine *e_u = u->GetEngine();
                const RailVehicleInfo *rvi_u = &e_u->u.rail;

                if (!HasBit(e_u->info.misc_flags, EF_RAIL_TILTS)) train_can_tilt = false;

                /* Cache wagon override sprite group. NULL is returned if there is none */
                u->tcache.cached_override = GetWagonOverrideSpriteSet(u->engine_type, u->cargo_type, u->gcache.first_engine);

                /* Reset colour map */
                u->colourmap = PAL_NONE;

                /* Update powered-wagon-status and visual effect */
                u->UpdateVisualEffect(true);

                if (rvi_v->pow_wag_power != 0 && rvi_u->railveh_type == RAILVEH_WAGON &&
                                UsesWagonOverride(u) && !HasBit(u->vcache.cached_vis_effect, VE_DISABLE_WAGON_POWER)) {
                        /* wagon is powered */
                        SetBit(u->flags, VRF_POWEREDWAGON); // cache 'powered' status
                } else {
                        ClrBit(u->flags, VRF_POWEREDWAGON);
                }

                if (!u->IsArticulatedPart()) {
                        /* Do not count powered wagons for the compatible railtypes, as wagons always
                           have railtype normal */
                        if (rvi_u->power > 0) {
                                this->compatible_railtypes |= GetRailTypeInfo(u->railtype)->powered_railtypes;
                        }

                        /* Some electric engines can be allowed to run on normal rail. It happens to all
                         * existing electric engines when elrails are disabled and then re-enabled */
                        if (HasBit(u->flags, VRF_EL_ENGINE_ALLOWED_NORMAL_RAIL)) {
                                u->railtype = RAILTYPE_RAIL;
                                u->compatible_railtypes |= RAILTYPES_RAIL;
                        }

                        /* max speed is the minimum of the speed limits of all vehicles in the consist */
                        if ((rvi_u->railveh_type != RAILVEH_WAGON || _settings_game.vehicle.wagon_speed_limits) && !UsesWagonOverride(u)) {
                                uint16 speed = GetVehicleProperty(u, PROP_TRAIN_SPEED, rvi_u->max_speed);
                                if (speed != 0) max_speed = min(speed, max_speed);
                        }
                }

                uint16 new_cap = e_u->DetermineCapacity(u);
                if (allowed_changes & CCF_CAPACITY) {
                        /* Update vehicle capacity. */
                        if (u->cargo_cap > new_cap) u->cargo.Truncate(new_cap);
                        u->refit_cap = min(new_cap, u->refit_cap);
                        u->cargo_cap = new_cap;
                } else {
                        /* Verify capacity hasn't changed. */
                        if (new_cap != u->cargo_cap) ShowNewGrfVehicleError(u->engine_type, STR_NEWGRF_BROKEN, STR_NEWGRF_BROKEN_CAPACITY, GBUG_VEH_CAPACITY, true);
                }
                u->vcache.cached_cargo_age_period = GetVehicleProperty(u, PROP_TRAIN_CARGO_AGE_PERIOD, e_u->info.cargo_age_period);

                /* check the vehicle length (callback) */
                uint16 veh_len = CALLBACK_FAILED;
                if (e_u->GetGRF() != NULL && e_u->GetGRF()->grf_version >= 8) {
                        /* Use callback 36 */
                        veh_len = GetVehicleProperty(u, PROP_TRAIN_SHORTEN_FACTOR, CALLBACK_FAILED);

                        if (veh_len != CALLBACK_FAILED && veh_len >= VEHICLE_LENGTH) {
                                ErrorUnknownCallbackResult(e_u->GetGRFID(), CBID_VEHICLE_LENGTH, veh_len);
                        }
                } else if (HasBit(e_u->info.callback_mask, CBM_VEHICLE_LENGTH)) {
                        /* Use callback 11 */
                        veh_len = GetVehicleCallback(CBID_VEHICLE_LENGTH, 0, 0, u->engine_type, u);
                }
                if (veh_len == CALLBACK_FAILED) veh_len = rvi_u->shorten_factor;
                veh_len = VEHICLE_LENGTH - Clamp(veh_len, 0, VEHICLE_LENGTH - 1);

                if (allowed_changes & CCF_LENGTH) {
                        /* Update vehicle length. */
                        u->gcache.cached_veh_length = veh_len;
                } else {
                        /* Verify length hasn't changed. */
                        if (veh_len != u->gcache.cached_veh_length) VehicleLengthChanged(u);
                }

                this->gcache.cached_total_length += u->gcache.cached_veh_length;
                this->InvalidateNewGRFCache();
                u->InvalidateNewGRFCache();
        }

        /* store consist weight/max speed in cache */
        this->vcache.cached_max_speed = max_speed;
        this->tcache.cached_tilt = train_can_tilt;
        this->tcache.cached_max_curve_speed = this->GetCurveSpeedLimit();

        /* recalculate cached weights and power too (we do this *after* the rest, so it is known which wagons are powered and need extra weight added) */
        this->CargoChanged();

        if (this->IsFrontEngine()) {
                this->UpdateAcceleration();
                SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
                InvalidateWindowData(WC_VEHICLE_REFIT, this->index, VIWD_CONSIST_CHANGED);
                InvalidateWindowData(WC_VEHICLE_ORDERS, this->index, VIWD_CONSIST_CHANGED);
                InvalidateNewGRFInspectWindow(GSF_TRAINS, this->index);
        }
}

/**
 * Get the stop location of (the center) of the front vehicle of a train at
 * a platform of a station.
 * @param station_id     the ID of the station where we're stopping
 * @param tile           the tile where the vehicle currently is
 * @param v              the vehicle to get the stop location of
 * @param station_ahead  'return' the amount of 1/16th tiles in front of the train
 * @param station_length 'return' the station length in 1/16th tiles
 * @return the location, calculated from the begin of the station to stop at.
 */
int GetTrainStopLocation(StationID station_id, TileIndex tile, const Train *v, int *station_ahead, int *station_length)
{
        const Station *st = Station::Get(station_id);
        *station_ahead  = st->GetPlatformLength(tile, DirToDiagDir(v->direction)) * TILE_SIZE;
        *station_length = st->GetPlatformLength(tile) * TILE_SIZE;

        /* Default to the middle of the station for stations stops that are not in
         * the order list like intermediate stations when non-stop is disabled */
        OrderStopLocation osl = OSL_PLATFORM_MIDDLE;
        if (v->gcache.cached_total_length >= *station_length) {
                /* The train is longer than the station, make it stop at the far end of the platform */
                osl = OSL_PLATFORM_FAR_END;
        } else if (v->current_order.IsType(OT_GOTO_STATION) && v->current_order.GetDestination() == station_id) {
                osl = v->current_order.GetStopLocation();
        }

        /* The stop location of the FRONT! of the train */
        int stop;
        switch (osl) {
                default: NOT_REACHED();

                case OSL_PLATFORM_NEAR_END:
                        stop = v->gcache.cached_total_length;
                        break;

                case OSL_PLATFORM_MIDDLE:
                        stop = *station_length - (*station_length - v->gcache.cached_total_length) / 2;
                        break;

                case OSL_PLATFORM_FAR_END:
                        stop = *station_length;
                        break;
        }

        /* Subtract half the front vehicle length of the train so we get the real
         * stop location of the train. */
        return stop - (v->gcache.cached_veh_length + 1) / 2;
}


/**
 * Computes train speed limit caused by curves
 * @return imposed speed limit
 */
int Train::GetCurveSpeedLimit() const
{
        assert(this->First() == this);

        static const int absolute_max_speed = UINT16_MAX;
        int max_speed = absolute_max_speed;

        if (_settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) return max_speed;

        int curvecount[2] = {0, 0};

        /* first find the curve speed limit */
        int numcurve = 0;
        int sum = 0;
        int pos = 0;
        int lastpos = -1;
        for (const Vehicle *u = this; u->Next() != NULL; u = u->Next(), pos++) {
                Direction this_dir = u->direction;
                Direction next_dir = u->Next()->direction;

                DirDiff dirdiff = DirDifference(this_dir, next_dir);
                if (dirdiff == DIRDIFF_SAME) continue;

                if (dirdiff == DIRDIFF_45LEFT) curvecount[0]++;
                if (dirdiff == DIRDIFF_45RIGHT) curvecount[1]++;
                if (dirdiff == DIRDIFF_45LEFT || dirdiff == DIRDIFF_45RIGHT) {
                        if (lastpos != -1) {
                                numcurve++;
                                sum += pos - lastpos;
                                if (pos - lastpos == 1 && max_speed > 88) {
                                        max_speed = 88;
                                }
                        }
                        lastpos = pos;
                }

                /* if we have a 90 degree turn, fix the speed limit to 60 */
                if (dirdiff == DIRDIFF_90LEFT || dirdiff == DIRDIFF_90RIGHT) {
                        max_speed = 61;
                }
        }

        if (numcurve > 0 && max_speed > 88) {
                if (curvecount[0] == 1 && curvecount[1] == 1) {
                        max_speed = absolute_max_speed;
                } else {
                        sum /= numcurve;
                        max_speed = 232 - (13 - Clamp(sum, 1, 12)) * (13 - Clamp(sum, 1, 12));
                }
        }

        if (max_speed != absolute_max_speed) {
                /* Apply the engine's rail type curve speed advantage, if it slowed by curves */
                const RailtypeInfo *rti = GetRailTypeInfo(this->railtype);
                max_speed += (max_speed / 2) * rti->curve_speed;

                if (this->tcache.cached_tilt) {
                        /* Apply max_speed bonus of 20% for a tilting train */
                        max_speed += max_speed / 5;
                }
        }

        return max_speed;
}

static uint FindTunnelPrevTrain(const Train *t, Vehicle **vv = NULL)
{
        assert(maptile_is_rail_tunnel(t->tile));
        assert(t->trackdir == TRACKDIR_WORMHOLE);

        VehicleTileIterator iter (t->tile);
        Vehicle *closest = NULL;
        uint dist;

        switch (GetTunnelBridgeDirection(t->tile)) {
                default: NOT_REACHED();

                case DIAGDIR_NE:
                        while (!iter.finished()) {
                                Vehicle *v = iter.next();
                                int pos = v->x_pos;
                                if (pos <= t->x_pos) continue; // v is behind
                                if (closest == NULL || pos < closest->x_pos) {
                                        closest = v;
                                } else {
                                        assert (pos != closest->x_pos);
                                }
                        }
                        dist = closest == NULL ? UINT_MAX : closest->x_pos - t->x_pos;
                        break;

                case DIAGDIR_NW:
                        while (!iter.finished()) {
                                Vehicle *v = iter.next();
                                int pos = v->y_pos;
                                if (pos <= t->y_pos) continue; // v is behind
                                if (closest == NULL || pos < closest->y_pos) {
                                        closest = v;
                                } else {
                                        assert (pos != closest->y_pos);
                                }
                        }
                        dist = closest == NULL ? UINT_MAX : closest->y_pos - t->y_pos;
                        break;

                case DIAGDIR_SW:
                        while (!iter.finished()) {
                                Vehicle *v = iter.next();
                                int pos = v->x_pos;
                                if (pos >= t->x_pos) continue; // v is behind
                                if (closest == NULL || pos > closest->x_pos) {
                                        closest = v;
                                } else {
                                        assert (pos != closest->x_pos);
                                }
                        }
                        dist = closest == NULL ? UINT_MAX : t->x_pos - closest->x_pos;
                        break;

                case DIAGDIR_SE:
                        while (!iter.finished()) {
                                Vehicle *v = iter.next();
                                int pos = v->y_pos;
                                if (pos >= t->y_pos) continue; // v is behind
                                if (closest == NULL || pos > closest->y_pos) {
                                        closest = v;
                                } else {
                                        assert (pos != closest->y_pos);
                                }
                        }
                        dist = closest == NULL ? UINT_MAX : t->y_pos - closest->y_pos;
                        break;
        }

        if (vv != NULL) *vv = closest;

        return dist;
}

/**
 * Calculates the maximum speed of the vehicle under its current conditions.
 * @return Maximum speed of the vehicle.
 */
int Train::GetCurrentMaxSpeed() const
{
        int max_speed = _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL ?
                        this->gcache.cached_max_track_speed :
                        this->tcache.cached_max_curve_speed;

        if (_settings_game.vehicle.train_acceleration_model == AM_REALISTIC && IsRailStationTile(this->tile)) {
                StationID sid = GetStationIndex(this->tile);
                if (this->current_order.ShouldStopAtStation(this, sid)) {
                        int station_ahead;
                        int station_length;
                        int stop_at = GetTrainStopLocation(sid, this->tile, this, &station_ahead, &station_length);

                        /* The distance to go is whatever is still ahead of the train minus the
                         * distance from the train's stop location to the end of the platform */
                        int distance_to_go = station_ahead / TILE_SIZE - (station_length - stop_at) / TILE_SIZE;

                        if (distance_to_go > 0) {
                                int st_max_speed = 120;

                                int delta_v = this->cur_speed / (distance_to_go + 1);
                                if (max_speed > (this->cur_speed - delta_v)) {
                                        st_max_speed = this->cur_speed - (delta_v / 10);
                                }

                                st_max_speed = max(st_max_speed, 25 * distance_to_go);
                                max_speed = min(max_speed, st_max_speed);
                        }
                }
        }

        for (const Train *u = this; u != NULL; u = u->Next()) {
                if (_settings_game.vehicle.train_acceleration_model == AM_REALISTIC && u->trackdir == TRACKDIR_DEPOT) {
                        max_speed = min(max_speed, 61);
                        break;
                }

                /* Vehicle is on the middle part of a bridge. */
                if (u->trackdir == TRACKDIR_WORMHOLE && !(u->vehstatus & VS_HIDDEN)) {
                        max_speed = min(max_speed, GetBridgeSpec(GetRailBridgeType(u->tile))->speed);
                }
        }

        if (this->trackdir == TRACKDIR_WORMHOLE && (this->vehstatus & VS_HIDDEN) && maptile_has_tunnel_signal(this->tile, false)) {
                Vehicle *v;
                uint dist = FindTunnelPrevTrain(this, &v);

                if (dist <= TILE_SIZE) {
                        max_speed = 0;
                } else if (v != NULL) {
                        max_speed = min(max_speed, (dist - TILE_SIZE) * this->GetAdvanceDistance() / 2);
                        if (dist < 2 * TILE_SIZE) max_speed = min(max_speed, v->cur_speed);
                }
        }

        max_speed = min(max_speed, this->current_order.GetMaxSpeed());
        return min(max_speed, this->gcache.cached_max_track_speed);
}

/** Update acceleration of the train from the cached power and weight. */
void Train::UpdateAcceleration()
{
        assert(this->IsFrontEngine() || this->IsFreeWagon());

        uint power = this->gcache.cached_power;
        uint weight = this->gcache.cached_weight;
        assert(weight != 0);
        this->acceleration = Clamp(power / weight * 4, 1, 255);
}

/**
 * Get the width of a train vehicle image in the GUI.
 * @param offset Additional offset for positioning the sprite; set to NULL if not needed
 * @return Width in pixels
 */
int Train::GetDisplayImageWidth(Point *offset) const
{
        int reference_width = TRAININFO_DEFAULT_VEHICLE_WIDTH;
        int vehicle_pitch = 0;

        const Engine *e = this->GetEngine();
        if (e->GetGRF() != NULL && is_custom_sprite(e->u.rail.image_index)) {
                reference_width = e->GetGRF()->traininfo_vehicle_width;
                vehicle_pitch = e->GetGRF()->traininfo_vehicle_pitch;
        }

        if (offset != NULL) {
                offset->x = ScaleGUITrad(reference_width) / 2;
                offset->y = ScaleGUITrad(vehicle_pitch);
        }
        return ScaleGUITrad(this->gcache.cached_veh_length * reference_width / VEHICLE_LENGTH);
}

static SpriteID GetDefaultTrainSprite(uint8 spritenum, Direction direction)
{
        assert(IsValidImageIndex<VEH_TRAIN>(spritenum));
        return ((direction + _engine_sprite_add[spritenum]) & _engine_sprite_and[spritenum]) + _engine_sprite_base[spritenum];
}

/**
 * Get the sprite to display the train.
 * @param direction Direction of view/travel.
 * @param image_type Visualisation context.
 * @return Sprite to display.
 */
void Train::GetImage(Direction direction, EngineImageType image_type, VehicleSpriteSeq *result) const
{
        uint8 spritenum = this->spritenum;

        if (HasBit(this->flags, VRF_REVERSE_DIRECTION)) direction = ReverseDir(direction);

        if (is_custom_sprite(spritenum)) {
                GetCustomVehicleSprite(this, (Direction)(direction + 4 * IS_CUSTOM_SECONDHEAD_SPRITE(spritenum)), image_type, result);
                if (result->IsValid()) return;

                spritenum = this->GetEngine()->original_image_index;
        }

        assert(IsValidImageIndex<VEH_TRAIN>(spritenum));
        SpriteID sprite = GetDefaultTrainSprite(spritenum, direction);

        if (this->cargo.StoredCount() >= this->cargo_cap / 2U) sprite += _wagon_full_adder[spritenum];

        result->Set(sprite);
}

static void GetRailIcon(EngineID engine, bool rear_head, int &y, EngineImageType image_type, VehicleSpriteSeq *result)
{
        const Engine *e = Engine::Get(engine);
        Direction dir = rear_head ? DIR_E : DIR_W;
        uint8 spritenum = e->u.rail.image_index;

        if (is_custom_sprite(spritenum)) {
                GetCustomVehicleIcon(engine, dir, image_type, result);
                if (result->IsValid()) {
                        if (e->GetGRF() != NULL) {
                                y += ScaleGUITrad(e->GetGRF()->traininfo_vehicle_pitch);
                        }
                        return;
                }

                spritenum = Engine::Get(engine)->original_image_index;
        }

        if (rear_head) spritenum++;

        result->Set(GetDefaultTrainSprite(spritenum, DIR_W));
}

void DrawTrainEngine (BlitArea *dpi, int left, int right, int preferred_x,
        int y, EngineID engine, PaletteID pal, EngineImageType image_type)
{
        if (RailVehInfo(engine)->railveh_type == RAILVEH_MULTIHEAD) {
                int yf = y;
                int yr = y;

                VehicleSpriteSeq seqf, seqr;
                GetRailIcon(engine, false, yf, image_type, &seqf);
                GetRailIcon(engine, true, yr, image_type, &seqr);

                Rect rectf, rectr;
                seqf.GetBounds(&rectf);
                seqr.GetBounds(&rectr);

                preferred_x = Clamp(preferred_x,
                                left - UnScaleGUI(rectf.left) + ScaleGUITrad(14),
                                right - UnScaleGUI(rectr.right) - ScaleGUITrad(15));

                seqf.Draw (dpi, preferred_x - ScaleGUITrad(14), yf, pal, pal == PALETTE_CRASH);
                seqr.Draw (dpi, preferred_x + ScaleGUITrad(15), yr, pal, pal == PALETTE_CRASH);
        } else {
                VehicleSpriteSeq seq;
                GetRailIcon(engine, false, y, image_type, &seq);

                Rect rect;
                seq.GetBounds(&rect);
                preferred_x = Clamp(preferred_x,
                                left - UnScaleGUI(rect.left),
                                right - UnScaleGUI(rect.right));

                seq.Draw (dpi, preferred_x, y, pal, pal == PALETTE_CRASH);
        }
}

/**
 * Get the size of the sprite of a train sprite heading west, or both heads (used for lists).
 * @param engine The engine to get the sprite from.
 * @param[out] width The width of the sprite.
 * @param[out] height The height of the sprite.
 * @param[out] xoffs Number of pixels to shift the sprite to the right.
 * @param[out] yoffs Number of pixels to shift the sprite downwards.
 * @param image_type Context the sprite is used in.
 */
void GetTrainSpriteSize(EngineID engine, uint &width, uint &height, int &xoffs, int &yoffs, EngineImageType image_type)
{
        int y = 0;

        VehicleSpriteSeq seq;
        GetRailIcon(engine, false, y, image_type, &seq);

        Rect rect;
        seq.GetBounds(&rect);

        width  = UnScaleGUI(rect.right - rect.left + 1);
        height = UnScaleGUI(rect.bottom - rect.top + 1);
        xoffs  = UnScaleGUI(rect.left);
        yoffs  = UnScaleGUI(rect.top);

        if (RailVehInfo(engine)->railveh_type == RAILVEH_MULTIHEAD) {
                GetRailIcon(engine, true, y, image_type, &seq);
                seq.GetBounds(&rect);

                /* Calculate values relative to an imaginary center between the two sprites. */
                width = ScaleGUITrad(TRAININFO_DEFAULT_VEHICLE_WIDTH) + UnScaleGUI(rect.right) - xoffs;
                height = max<uint>(height, UnScaleGUI(rect.bottom - rect.top + 1));
                xoffs  = xoffs - ScaleGUITrad(TRAININFO_DEFAULT_VEHICLE_WIDTH) / 2;
                yoffs  = min(yoffs, UnScaleGUI(rect.top));
        }
}

/**
 * Build a railroad wagon.
 * @param tile     tile of the depot where rail-vehicle is built.
 * @param flags    type of operation.
 * @param e        the engine to build.
 * @param ret[out] the vehicle that has been built.
 * @return the cost of this operation or an error.
 */
static CommandCost CmdBuildRailWagon(TileIndex tile, DoCommandFlag flags, const Engine *e, Vehicle **ret)
{
        const RailVehicleInfo *rvi = &e->u.rail;

        /* Check that the wagon can drive on the track in question */
        if (!IsCompatibleRail(rvi->railtype, GetRailType(tile))) return CMD_ERROR;

        if (flags & DC_EXEC) {
                Train *v = new Train();
                *ret = v;
                v->spritenum = rvi->image_index;

                v->engine_type = e->index;
                v->gcache.first_engine = INVALID_ENGINE; // needs to be set before first callback

                DiagDirection dir = GetGroundDepotDirection(tile);

                v->direction = DiagDirToDir(dir);
                v->tile = tile;

                int x = TileX(tile) * TILE_SIZE | _vehicle_initial_x_fract[dir];
                int y = TileY(tile) * TILE_SIZE | _vehicle_initial_y_fract[dir];

                v->x_pos = x;
                v->y_pos = y;
                v->z_pos = GetSlopePixelZ(x, y);
                v->owner = _current_company;
                v->trackdir = TRACKDIR_DEPOT;
                v->vehstatus = VS_HIDDEN | VS_DEFPAL;

                v->SetWagon();

                v->SetFreeWagon();
                InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);

                v->cargo_type = e->GetDefaultCargoType();
                v->cargo_cap = rvi->capacity;
                v->refit_cap = 0;

                v->railtype = rvi->railtype;

                v->date_of_last_service = _date;
                v->build_year = _cur_year;
                v->sprite_seq.Set(SPR_IMG_QUERY);
                v->random_bits = VehicleRandomBits();

                v->group_id = DEFAULT_GROUP;

                AddArticulatedParts(v);

                _new_vehicle_id = v->index;

                v->UpdatePosition();
                v->First()->ConsistChanged(CCF_ARRANGE);
                UpdateTrainGroupID(v->First());

                CheckConsistencyOfArticulatedVehicle(v);

                /* Try to connect the vehicle to one of free chains of wagons. */
                Train *w;
                FOR_ALL_TRAINS(w) {
                        if (w->tile == tile &&              ///< Same depot
                                        w->IsFreeWagon() &&             ///< A free wagon chain
                                        w->engine_type == e->index &&   ///< Same type
                                        w->First() != v &&              ///< Don't connect to ourself
                                        !(w->vehstatus & VS_CRASHED)) { ///< Not crashed/flooded
                                DoCommand(0, v->index | 1 << 20, w->Last()->index, DC_EXEC, CMD_MOVE_RAIL_VEHICLE);
                                break;
                        }
                }
        }

        return CommandCost();
}

/** Move all free vehicles in the depot to the train */
static void NormalizeTrainVehInDepot(const Train *u)
{
        const Train *v;
        FOR_ALL_TRAINS(v) {
                if (v->IsFreeWagon() && v->tile == u->tile &&
                                v->trackdir == TRACKDIR_DEPOT) {
                        if (DoCommand(0, v->index | 1 << 20, u->index, DC_EXEC,
                                        CMD_MOVE_RAIL_VEHICLE).Failed())
                                break;
                }
        }
}

static void AddRearEngineToMultiheadedTrain(Train *v)
{
        Train *u = new Train();
        v->value >>= 1;
        u->value = v->value;
        u->direction = v->direction;
        u->owner = v->owner;
        u->tile = v->tile;
        u->x_pos = v->x_pos;
        u->y_pos = v->y_pos;
        u->z_pos = v->z_pos;
        u->trackdir = TRACKDIR_DEPOT;
        u->vehstatus = v->vehstatus & ~VS_STOPPED;
        u->spritenum = v->spritenum + 1;
        u->cargo_type = v->cargo_type;
        u->cargo_subtype = v->cargo_subtype;
        u->cargo_cap = v->cargo_cap;
        u->refit_cap = v->refit_cap;
        u->railtype = v->railtype;
        u->engine_type = v->engine_type;
        u->date_of_last_service = v->date_of_last_service;
        u->build_year = v->build_year;
        u->sprite_seq.Set(SPR_IMG_QUERY);
        u->random_bits = VehicleRandomBits();
        v->SetMultiheaded();
        u->SetMultiheaded();
        v->SetNext(u);
        u->UpdatePosition();

        /* Now we need to link the front and rear engines together */
        v->other_multiheaded_part = u;
        u->other_multiheaded_part = v;
}

/**
 * Build a railroad vehicle.
 * @param tile     tile of the depot where rail-vehicle is built.
 * @param flags    type of operation.
 * @param e        the engine to build.
 * @param data     bit 0 prevents any free cars from being added to the train.
 * @param ret[out] the vehicle that has been built.
 * @return the cost of this operation or an error.
 */
CommandCost CmdBuildRailVehicle(TileIndex tile, DoCommandFlag flags, const Engine *e, uint16 data, Vehicle **ret)
{
        const RailVehicleInfo *rvi = &e->u.rail;

        if (rvi->railveh_type == RAILVEH_WAGON) return CmdBuildRailWagon(tile, flags, e, ret);

        /* Check if depot and new engine uses the same kind of tracks *
         * We need to see if the engine got power on the tile to avoid electric engines in non-electric depots */
        if (!HasPowerOnRail(rvi->railtype, GetRailType(tile))) return CMD_ERROR;

        if (flags & DC_EXEC) {
                DiagDirection dir = GetGroundDepotDirection(tile);
                int x = TileX(tile) * TILE_SIZE + _vehicle_initial_x_fract[dir];
                int y = TileY(tile) * TILE_SIZE + _vehicle_initial_y_fract[dir];

                Train *v = new Train();
                *ret = v;
                v->direction = DiagDirToDir(dir);
                v->tile = tile;
                v->owner = _current_company;
                v->x_pos = x;
                v->y_pos = y;
                v->z_pos = GetSlopePixelZ(x, y);
                v->trackdir = TRACKDIR_DEPOT;
                v->vehstatus = VS_HIDDEN | VS_STOPPED | VS_DEFPAL;
                v->spritenum = rvi->image_index;
                v->cargo_type = e->GetDefaultCargoType();
                v->cargo_cap = rvi->capacity;
                v->refit_cap = 0;
                v->last_station_visited = INVALID_STATION;
                v->last_loading_station = INVALID_STATION;

                v->engine_type = e->index;
                v->gcache.first_engine = INVALID_ENGINE; // needs to be set before first callback

                v->reliability = e->reliability;
                v->reliability_spd_dec = e->reliability_spd_dec;
                v->max_age = e->GetLifeLengthInDays();

                v->railtype = rvi->railtype;
                _new_vehicle_id = v->index;

                v->SetServiceInterval(Company::Get(_current_company)->settings.vehicle.servint_trains);
                v->date_of_last_service = _date;
                v->build_year = _cur_year;
                v->sprite_seq.Set(SPR_IMG_QUERY);
                v->random_bits = VehicleRandomBits();

                if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) SetBit(v->vehicle_flags, VF_BUILT_AS_PROTOTYPE);
                v->SetServiceIntervalIsPercent(Company::Get(_current_company)->settings.vehicle.servint_ispercent);

                v->group_id = DEFAULT_GROUP;

                v->SetFrontEngine();
                v->SetEngine();

                v->UpdatePosition();

                if (rvi->railveh_type == RAILVEH_MULTIHEAD) {
                        AddRearEngineToMultiheadedTrain(v);
                } else {
                        AddArticulatedParts(v);
                }

                v->ConsistChanged(CCF_ARRANGE);
                UpdateTrainGroupID(v);

                if (!HasBit(data, 0) && !(flags & DC_AUTOREPLACE)) { // check if the cars should be added to the new vehicle
                        NormalizeTrainVehInDepot(v);
                }

                CheckConsistencyOfArticulatedVehicle(v);
        }

        return CommandCost();
}

static Train *FindGoodVehiclePos(const Train *src)
{
        EngineID eng = src->engine_type;
        TileIndex tile = src->tile;

        Train *dst;
        FOR_ALL_TRAINS(dst) {
                if (dst->IsFreeWagon() && dst->tile == tile && !(dst->vehstatus & VS_CRASHED)) {
                        /* check so all vehicles in the line have the same engine. */
                        Train *t = dst;
                        while (t->engine_type == eng) {
                                t = t->Next();
                                if (t == NULL) return dst;
                        }
                }
        }

        return NULL;
}

/** Helper type for lists/vectors of trains */
typedef SmallVector<Train *, 16> TrainList;

/**
 * Make a backup of a train into a train list.
 * @param list to make the backup in
 * @param t    the train to make the backup of
 */
static void MakeTrainBackup(TrainList &list, Train *t)
{
        for (; t != NULL; t = t->Next()) *list.Append() = t;
}

/**
 * Restore the train from the backup list.
 * @param list the train to restore.
 */
static void RestoreTrainBackup(TrainList &list)
{
        /* No train, nothing to do. */
        if (list.Length() == 0) return;

        Train *prev = NULL;
        /* Iterate over the list and rebuild it. */
        for (Train **iter = list.Begin(); iter != list.End(); iter++) {
                Train *t = *iter;
                if (prev != NULL) {
                        prev->SetNext(t);
                } else if (t->Previous() != NULL) {
                        /* Make sure the head of the train is always the first in the chain. */
                        t->Previous()->SetNext(NULL);
                }
                prev = t;
        }
}

/**
 * Remove the given wagon from its consist.
 * @param part the part of the train to remove.
 * @param chain whether to remove the whole chain.
 */
static void RemoveFromConsist(Train *part, bool chain = false)
{
        Train *tail = chain ? part->Last() : part->GetLastEnginePart();

        /* Unlink at the front, but make it point to the next
         * vehicle after the to be remove part. */
        if (part->Previous() != NULL) part->Previous()->SetNext(tail->Next());

        /* Unlink at the back */
        tail->SetNext(NULL);
}

/**
 * Inserts a chain into the train at dst.
 * @param dst   the place where to append after.
 * @param chain the chain to actually add.
 */
static void InsertInConsist(Train *dst, Train *chain)
{
        /* We do not want to add something in the middle of an articulated part. */
        assert(dst->Next() == NULL || !dst->Next()->IsArticulatedPart());

        chain->Last()->SetNext(dst->Next());
        dst->SetNext(chain);
}

/**
 * Normalise the dual heads in the train, i.e. if one is
 * missing move that one to this train.
 * @param t the train to normalise.
 */
static void NormaliseDualHeads(Train *t)
{
        for (; t != NULL; t = t->GetNextVehicle()) {
                if (!t->IsMultiheaded() || !t->IsEngine()) continue;

                /* Make sure that there are no free cars before next engine */
                Train *u;
                for (u = t; u->Next() != NULL && !u->Next()->IsEngine(); u = u->Next()) {}

                if (u == t->other_multiheaded_part) continue;

                /* Remove the part from the 'wrong' train */
                RemoveFromConsist(t->other_multiheaded_part);
                /* And add it to the 'right' train */
                InsertInConsist(u, t->other_multiheaded_part);
        }
}

/**
 * Normalise the sub types of the parts in this chain.
 * @param chain the chain to normalise.
 */
static void NormaliseSubtypes(Train *chain)
{
        /* Nothing to do */
        if (chain == NULL) return;

        /* We must be the first in the chain. */
        assert(chain->Previous() == NULL);

        /* Set the appropriate bits for the first in the chain. */
        if (chain->IsWagon()) {
                chain->SetFreeWagon();
        } else {
                assert(chain->IsEngine());
                chain->SetFrontEngine();
        }

        /* Now clear the bits for the rest of the chain */
        for (Train *t = chain->Next(); t != NULL; t = t->Next()) {
                t->ClearFreeWagon();
                t->ClearFrontEngine();
        }
}

/**
 * Check/validate whether we may actually build a new train.
 * @note All vehicles are/were 'heads' of their chains.
 * @param original_dst The original destination chain.
 * @param dst          The destination chain after constructing the train.
 * @param original_dst The original source chain.
 * @param dst          The source chain after constructing the train.
 * @return possible error of this command.
 */
static CommandCost CheckNewTrain(Train *original_dst, Train *dst, Train *original_src, Train *src)
{
        /* Just add 'new' engines and subtract the original ones.
         * If that's less than or equal to 0 we can be sure we did
         * not add any engines (read: trains) along the way. */
        if ((src          != NULL && src->IsEngine()          ? 1 : 0) +
                        (dst          != NULL && dst->IsEngine()          ? 1 : 0) -
                        (original_src != NULL && original_src->IsEngine() ? 1 : 0) -
                        (original_dst != NULL && original_dst->IsEngine() ? 1 : 0) <= 0) {
                return CommandCost();
        }

        /* Get a free unit number and check whether it's within the bounds.
         * There will always be a maximum of one new train. */
        if (GetFreeUnitNumber(VEH_TRAIN) <= _settings_game.vehicle.max_trains) return CommandCost();

        return_cmd_error(STR_ERROR_TOO_MANY_VEHICLES_IN_GAME);
}

/**
 * Check whether the train parts can be attached.
 * @param t the train to check
 * @return possible error of this command.
 */
static CommandCost CheckTrainAttachment(Train *t)
{
        /* No multi-part train, no need to check. */
        if (t == NULL || t->Next() == NULL || !t->IsEngine()) return CommandCost();

        /* The maximum length for a train. For each part we decrease this by one
         * and if the result is negative the train is simply too long. */
        int allowed_len = _settings_game.vehicle.max_train_length * TILE_SIZE - t->gcache.cached_veh_length;

        Train *head = t;
        Train *prev = t;

        /* Break the prev -> t link so it always holds within the loop. */
        t = t->Next();
        prev->SetNext(NULL);

        /* Make sure the cache is cleared. */
        head->InvalidateNewGRFCache();

        while (t != NULL) {
                allowed_len -= t->gcache.cached_veh_length;

                Train *next = t->Next();

                /* Unlink the to-be-added piece; it is already unlinked from the previous
                 * part due to the fact that the prev -> t link is broken. */
                t->SetNext(NULL);

                /* Don't check callback for articulated or rear dual headed parts */
                if (!t->IsArticulatedPart() && !t->IsRearDualheaded()) {
                        /* Back up and clear the first_engine data to avoid using wagon override group */
                        EngineID first_engine = t->gcache.first_engine;
                        t->gcache.first_engine = INVALID_ENGINE;

                        /* We don't want the cache to interfere. head's cache is cleared before
                         * the loop and after each callback does not need to be cleared here. */
                        t->InvalidateNewGRFCache();

                        uint16 callback = GetVehicleCallbackParent(CBID_TRAIN_ALLOW_WAGON_ATTACH, 0, 0, head->engine_type, t, head);

                        /* Restore original first_engine data */
                        t->gcache.first_engine = first_engine;

                        /* We do not want to remember any cached variables from the test run */
                        t->InvalidateNewGRFCache();
                        head->InvalidateNewGRFCache();

                        if (callback != CALLBACK_FAILED) {
                                /* A failing callback means everything is okay */
                                StringID error = STR_NULL;

                                if (head->GetGRF()->grf_version < 8) {
                                        if (callback == 0xFD) error = STR_ERROR_INCOMPATIBLE_RAIL_TYPES;
                                        if (callback  < 0xFD) error = GetGRFStringID(head->GetGRFID(), 0xD000 + callback);
                                        if (callback >= 0x100) ErrorUnknownCallbackResult(head->GetGRFID(), CBID_TRAIN_ALLOW_WAGON_ATTACH, callback);
                                } else {
                                        if (callback < 0x400) {
                                                error = GetGRFStringID(head->GetGRFID(), 0xD000 + callback);
                                        } else {
                                                switch (callback) {
                                                        case 0x400: // allow if railtypes match (always the case for OpenTTD)
                                                        case 0x401: // allow
                                                                break;

                                                        default:    // unknown reason -> disallow
                                                        case 0x402: // disallow attaching
                                                                error = STR_ERROR_INCOMPATIBLE_RAIL_TYPES;
                                                                break;
                                                }
                                        }
                                }

                                if (error != STR_NULL) return_cmd_error(error);
                        }
                }

                /* And link it to the new part. */
                prev->SetNext(t);
                prev = t;
                t = next;
        }

        if (allowed_len < 0) return_cmd_error(STR_ERROR_TRAIN_TOO_LONG);
        return CommandCost();
}

/**
 * Validate whether we are going to create valid trains.
 * @note All vehicles are/were 'heads' of their chains.
 * @param original_dst The original destination chain.
 * @param dst          The destination chain after constructing the train.
 * @param original_dst The original source chain.
 * @param dst          The source chain after constructing the train.
 * @param check_limit  Whether to check the vehicle limit.
 * @return possible error of this command.
 */
static CommandCost ValidateTrains(Train *original_dst, Train *dst, Train *original_src, Train *src, bool check_limit)
{
        /* Check whether we may actually construct the trains. */
        CommandCost ret = CheckTrainAttachment(src);
        if (ret.Failed()) return ret;
        ret = CheckTrainAttachment(dst);
        if (ret.Failed()) return ret;

        /* Check whether we need to build a new train. */
        return check_limit ? CheckNewTrain(original_dst, dst, original_src, src) : CommandCost();
}

/**
 * Arrange the trains in the wanted way.
 * @param dst_head   The destination chain of the to be moved vehicle.
 * @param dst        The destination for the to be moved vehicle.
 * @param src_head   The source chain of the to be moved vehicle.
 * @param src        The to be moved vehicle.
 * @param move_chain Whether to move all vehicles after src or not.
 */
static void ArrangeTrains(Train **dst_head, Train *dst, Train **src_head, Train *src, bool move_chain)
{
        /* First determine the front of the two resulting trains */
        if (*src_head == *dst_head) {
                /* If we aren't moving part(s) to a new train, we are just moving the
                 * front back and there is not destination head. */
                *dst_head = NULL;
        } else if (*dst_head == NULL) {
                /* If we are moving to a new train the head of the move train would become
                 * the head of the new vehicle. */
                *dst_head = src;
        }

        if (src == *src_head) {
                /* If we are moving the front of a train then we are, in effect, creating
                 * a new head for the train. Point to that. Unless we are moving the whole
                 * train in which case there is not 'source' train anymore.
                 * In case we are a multiheaded part we want the complete thing to come
                 * with us, so src->GetNextUnit(), however... when we are e.g. a wagon
                 * that is followed by a rear multihead we do not want to include that. */
                *src_head = move_chain ? NULL :
                                (src->IsMultiheaded() ? src->GetNextUnit() : src->GetNextVehicle());
        }

        /* Now it's just simply removing the part that we are going to move from the
         * source train and *if* the destination is a not a new train add the chain
         * at the destination location. */
        RemoveFromConsist(src, move_chain);
        if (*dst_head != src) InsertInConsist(dst, src);

        /* Now normalise the dual heads, that is move the dual heads around in such
         * a way that the head and rear of a dual head are in the same train */
        NormaliseDualHeads(*src_head);
        NormaliseDualHeads(*dst_head);
}

/**
 * Normalise the head of the train again, i.e. that is tell the world that
 * we have changed and update all kinds of variables.
 * @param head the train to update.
 */
static void NormaliseTrainHead(Train *head)
{
        /* Not much to do! */
        if (head == NULL) return;

        /* Tell the 'world' the train changed. */
        head->ConsistChanged(CCF_ARRANGE);
        UpdateTrainGroupID(head);

        /* Not a front engine, i.e. a free wagon chain. No need to do more. */
        if (!head->IsFrontEngine()) return;

        /* Update the refit button and window */
        InvalidateWindowData(WC_VEHICLE_REFIT, head->index, VIWD_CONSIST_CHANGED);
        SetWindowWidgetDirty(WC_VEHICLE_VIEW, head->index, WID_VV_REFIT);

        /* If we don't have a unit number yet, set one. */
        if (head->unitnumber != 0) return;
        head->unitnumber = GetFreeUnitNumber(VEH_TRAIN);
}

/**
 * Move a rail vehicle around inside the depot.
 * @param tile unused
 * @param flags type of operation
 *              Note: DC_AUTOREPLACE is set when autoreplace tries to undo its modifications or moves vehicles to temporary locations inside the depot.
 * @param p1 various bitstuffed elements
 * - p1 (bit  0 - 19) source vehicle index
 * - p1 (bit      20) move all vehicles following the source vehicle
 * - p1 (bit      31) do not show an error message on failure
 * @param p2 what wagon to put the source wagon AFTER, XXX - INVALID_VEHICLE to make a new line
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        VehicleID s = GB(p1, 0, 20);
        VehicleID d = GB(p2, 0, 20);
        bool move_chain = HasBit(p1, 20);

        Train *src = Train::GetIfValid(s);
        if (src == NULL) return CMD_ERROR;

        CommandCost ret = CheckOwnership(src->owner);
        if (ret.Failed()) return ret;

        /* Do not allow moving crashed vehicles inside the depot, it is likely to cause asserts later */
        if (src->vehstatus & VS_CRASHED) return CMD_ERROR;

        /* if nothing is selected as destination, try and find a matching vehicle to drag to. */
        Train *dst;
        if (d == INVALID_VEHICLE) {
                dst = src->IsEngine() ? NULL : FindGoodVehiclePos(src);
        } else {
                dst = Train::GetIfValid(d);
                if (dst == NULL) return CMD_ERROR;

                CommandCost ret = CheckOwnership(dst->owner);
                if (ret.Failed()) return ret;

                /* Do not allow appending to crashed vehicles, too */
                if (dst->vehstatus & VS_CRASHED) return CMD_ERROR;
        }

        /* if an articulated part is being handled, deal with its parent vehicle */
        src = src->GetFirstEnginePart();
        if (dst != NULL) {
                dst = dst->GetFirstEnginePart();
        }

        /* don't move the same vehicle.. */
        if (src == dst) return CommandCost();

        /* locate the head of the two chains */
        Train *src_head = src->First();
        Train *dst_head;
        if (dst != NULL) {
                dst_head = dst->First();
                if (dst_head->tile != src_head->tile) return CMD_ERROR;
                /* Now deal with articulated part of destination wagon */
                dst = dst->GetLastEnginePart();
        } else {
                dst_head = NULL;
        }

        if (src->IsRearDualheaded()) return_cmd_error(STR_ERROR_REAR_ENGINE_FOLLOW_FRONT);

        /* When moving all wagons, we can't have the same src_head and dst_head */
        if (move_chain && src_head == dst_head) return CommandCost();

        /* When moving a multiheaded part to be place after itself, bail out. */
        if (!move_chain && dst != NULL && dst->IsRearDualheaded() && src == dst->other_multiheaded_part) return CommandCost();

        /* Check if all vehicles in the source train are stopped inside a depot. */
        if (!src_head->IsStoppedInDepot()) return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);

        /* Check if all vehicles in the destination train are stopped inside a depot. */
        if (dst_head != NULL && !dst_head->IsStoppedInDepot()) return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);

        /* First make a backup of the order of the trains. That way we can do
         * whatever we want with the order and later on easily revert. */
        TrainList original_src;
        TrainList original_dst;

        MakeTrainBackup(original_src, src_head);
        MakeTrainBackup(original_dst, dst_head);

        /* Also make backup of the original heads as ArrangeTrains can change them.
         * For the destination head we do not care if it is the same as the source
         * head because in that case it's just a copy. */
        Train *original_src_head = src_head;
        Train *original_dst_head = (dst_head == src_head ? NULL : dst_head);

        /* We want this information from before the rearrangement, but execute this after the validation.
         * original_src_head can't be NULL; src is by definition != NULL, so src_head can't be NULL as
         * src->GetFirst() always yields non-NULL, so eventually original_src_head != NULL as well. */
        bool original_src_head_front_engine = original_src_head->IsFrontEngine();
        bool original_dst_head_front_engine = original_dst_head != NULL && original_dst_head->IsFrontEngine();

        /* (Re)arrange the trains in the wanted arrangement. */
        ArrangeTrains(&dst_head, dst, &src_head, src, move_chain);

        if ((flags & DC_AUTOREPLACE) == 0) {
                /* If the autoreplace flag is set we do not need to test for the validity
                 * because we are going to revert the train to its original state. As we
                 * assume the original state was correct autoreplace can skip this. */
                CommandCost ret = ValidateTrains(original_dst_head, dst_head, original_src_head, src_head, true);
                if (ret.Failed()) {
                        /* Restore the train we had. */
                        RestoreTrainBackup(original_src);
                        RestoreTrainBackup(original_dst);
                        return ret;
                }
        }

        /* do it? */
        if (flags & DC_EXEC) {
                /* Remove old heads from the statistics */
                if (original_src_head_front_engine) GroupStatistics::CountVehicle(original_src_head, -1);
                if (original_dst_head_front_engine) GroupStatistics::CountVehicle(original_dst_head, -1);

                /* First normalise the sub types of the chains. */
                NormaliseSubtypes(src_head);
                NormaliseSubtypes(dst_head);

                /* There are 14 different cases:
                 *  1) front engine gets moved to a new train, it stays a front engine.
                 *     a) the 'next' part is a wagon that becomes a free wagon chain.
                 *     b) the 'next' part is an engine that becomes a front engine.
                 *     c) there is no 'next' part, nothing else happens
                 *  2) front engine gets moved to another train, it is not a front engine anymore
                 *     a) the 'next' part is a wagon that becomes a free wagon chain.
                 *     b) the 'next' part is an engine that becomes a front engine.
                 *     c) there is no 'next' part, nothing else happens
                 *  3) front engine gets moved to later in the current train, it is not a front engine anymore.
                 *     a) the 'next' part is a wagon that becomes a free wagon chain.
                 *     b) the 'next' part is an engine that becomes a front engine.
                 *  4) free wagon gets moved
                 *     a) the 'next' part is a wagon that becomes a free wagon chain.
                 *     b) the 'next' part is an engine that becomes a front engine.
                 *     c) there is no 'next' part, nothing else happens
                 *  5) non front engine gets moved and becomes a new train, nothing else happens
                 *  6) non front engine gets moved within a train / to another train, nothing hapens
                 *  7) wagon gets moved, nothing happens
                 */
                if (src == original_src_head && src->IsEngine() && !src->IsFrontEngine()) {
                        /* Cases #2 and #3: the front engine gets trashed. */
                        DeleteWindowById(WC_VEHICLE_VIEW, src->index);
                        DeleteWindowById(WC_VEHICLE_ORDERS, src->index);
                        DeleteWindowById(WC_VEHICLE_REFIT, src->index);
                        DeleteWindowById(WC_VEHICLE_DETAILS, src->index);
                        DeleteWindowById(WC_VEHICLE_TIMETABLE, src->index);
                        DeleteNewGRFInspectWindow(GSF_TRAINS, src->index);
                        SetWindowDirty(WC_COMPANY, _current_company);

                        /* Delete orders, group stuff and the unit number as we're not the
                         * front of any vehicle anymore. */
                        DeleteVehicleOrders(src);
                        RemoveVehicleFromGroup(src);
                        src->unitnumber = 0;
                }

                /* We weren't a front engine but are becoming one. So
                 * we should be put in the default group. */
                if (original_src_head != src && dst_head == src) {
                        SetTrainGroupID(src, DEFAULT_GROUP);
                        SetWindowDirty(WC_COMPANY, _current_company);
                }

                /* Add new heads to statistics */
                if (src_head != NULL && src_head->IsFrontEngine()) GroupStatistics::CountVehicle(src_head, 1);
                if (dst_head != NULL && dst_head->IsFrontEngine()) GroupStatistics::CountVehicle(dst_head, 1);

                /* Handle 'new engine' part of cases #1b, #2b, #3b, #4b and #5 in NormaliseTrainHead. */
                NormaliseTrainHead(src_head);
                NormaliseTrainHead(dst_head);

                if ((flags & DC_NO_CARGO_CAP_CHECK) == 0) {
                        CheckCargoCapacity(src_head);
                        CheckCargoCapacity(dst_head);
                }

                if (src_head != NULL) src_head->First()->MarkDirty();
                if (dst_head != NULL) dst_head->First()->MarkDirty();

                /* We are undoubtedly changing something in the depot and train list. */
                InvalidateWindowData(WC_VEHICLE_DEPOT, src->tile);
                InvalidateWindowClassesData(WC_TRAINS_LIST, 0);
        } else {
                /* We don't want to execute what we're just tried. */
                RestoreTrainBackup(original_src);
                RestoreTrainBackup(original_dst);
        }

        return CommandCost();
}

/**
 * Sell a (single) train wagon/engine.
 * @param flags type of operation
 * @param t     the train wagon to sell
 * @param data  the selling mode
 * - data = 0: only sell the single dragged wagon/engine (and any belonging rear-engines)
 * - data = 1: sell the vehicle and all vehicles following it in the chain
 *             if the wagon is dragged, don't delete the possibly belonging rear-engine to some front
 * @param user  the user for the order backup.
 * @return the cost of this operation or an error
 */
CommandCost CmdSellRailWagon(DoCommandFlag flags, Vehicle *t, uint16 data, uint32 user)
{
        /* Sell a chain of vehicles or not? */
        bool sell_chain = HasBit(data, 0);

        Train *v = Train::From(t)->GetFirstEnginePart();
        Train *first = v->First();

        if (v->IsRearDualheaded()) return_cmd_error(STR_ERROR_REAR_ENGINE_FOLLOW_FRONT);

        /* First make a backup of the order of the train. That way we can do
         * whatever we want with the order and later on easily revert. */
        TrainList original;
        MakeTrainBackup(original, first);

        /* We need to keep track of the new head and the head of what we're going to sell. */
        Train *new_head = first;
        Train *sell_head = NULL;

        /* Split the train in the wanted way. */
        ArrangeTrains(&sell_head, NULL, &new_head, v, sell_chain);

        /* We don't need to validate the second train; it's going to be sold. */
        CommandCost ret = ValidateTrains(NULL, NULL, first, new_head, (flags & DC_AUTOREPLACE) == 0);
        if (ret.Failed()) {
                /* Restore the train we had. */
                RestoreTrainBackup(original);
                return ret;
        }

        if (first->orders.list == NULL && !OrderList::CanAllocateItem()) {
                /* Restore the train we had. */
                RestoreTrainBackup(original);
                return_cmd_error(STR_ERROR_NO_MORE_SPACE_FOR_ORDERS);
        }

        CommandCost cost(EXPENSES_NEW_VEHICLES);
        for (Train *t = sell_head; t != NULL; t = t->Next()) cost.AddCost(-t->value);

        /* do it? */
        if (flags & DC_EXEC) {
                /* First normalise the sub types of the chain. */
                NormaliseSubtypes(new_head);

                if (v == first && v->IsEngine() && !sell_chain && new_head != NULL && new_head->IsFrontEngine()) {
                        /* We are selling the front engine. In this case we want to
                         * 'give' the order, unit number and such to the new head. */
                        new_head->orders.list = first->orders.list;
                        new_head->AddToShared(first);
                        DeleteVehicleOrders(first);

                        /* Copy other important data from the front engine */
                        new_head->CopyVehicleConfigAndStatistics(first);
                        GroupStatistics::CountVehicle(new_head, 1); // after copying over the profit
                } else if (v->IsPrimaryVehicle() && data & (MAKE_ORDER_BACKUP_FLAG >> 20)) {
                        OrderBackup::Backup(v, user);
                }

                /* We need to update the information about the train. */
                NormaliseTrainHead(new_head);

                /* We are undoubtedly changing something in the depot and train list. */
                InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
                InvalidateWindowClassesData(WC_TRAINS_LIST, 0);

                /* Actually delete the sold 'goods' */
                delete sell_head;
        } else {
                /* We don't want to execute what we're just tried. */
                RestoreTrainBackup(original);
        }

        return cost;
}

void Train::UpdateDeltaXY(Direction direction)
{
        /* Set common defaults. */
        this->x_offs    = -1;
        this->y_offs    = -1;
        this->x_extent  =  3;
        this->y_extent  =  3;
        this->z_extent  =  6;
        this->x_bb_offs =  0;
        this->y_bb_offs =  0;

        if (!IsDiagonalDirection(direction)) {
                static const int _sign_table[] =
                {
                        /* x, y */
                        -1, -1, // DIR_N
                        -1,  1, // DIR_E
                         1,  1, // DIR_S
                         1, -1, // DIR_W
                };

                int half_shorten = (VEHICLE_LENGTH - this->gcache.cached_veh_length) / 2;

                /* For all straight directions, move the bound box to the centre of the vehicle, but keep the size. */
                this->x_offs -= half_shorten * _sign_table[direction];
                this->y_offs -= half_shorten * _sign_table[direction + 1];
                this->x_extent += this->x_bb_offs = half_shorten * _sign_table[direction];
                this->y_extent += this->y_bb_offs = half_shorten * _sign_table[direction + 1];
        } else {
                switch (direction) {
                                /* Shorten southern corner of the bounding box according the vehicle length
                                 * and center the bounding box on the vehicle. */
                        case DIR_NE:
                                this->x_offs    = 1 - (this->gcache.cached_veh_length + 1) / 2;
                                this->x_extent  = this->gcache.cached_veh_length - 1;
                                this->x_bb_offs = -1;
                                break;

                        case DIR_NW:
                                this->y_offs    = 1 - (this->gcache.cached_veh_length + 1) / 2;
                                this->y_extent  = this->gcache.cached_veh_length - 1;
                                this->y_bb_offs = -1;
                                break;

                                /* Move northern corner of the bounding box down according to vehicle length
                                 * and center the bounding box on the vehicle. */
                        case DIR_SW:
                                this->x_offs    = 1 + (this->gcache.cached_veh_length + 1) / 2 - VEHICLE_LENGTH;
                                this->x_extent  = VEHICLE_LENGTH - 1;
                                this->x_bb_offs = VEHICLE_LENGTH - this->gcache.cached_veh_length - 1;
                                break;

                        case DIR_SE:
                                this->y_offs    = 1 + (this->gcache.cached_veh_length + 1) / 2 - VEHICLE_LENGTH;
                                this->y_extent  = VEHICLE_LENGTH - 1;
                                this->y_bb_offs = VEHICLE_LENGTH - this->gcache.cached_veh_length - 1;
                                break;

                        default:
                                NOT_REACHED();
                }
        }
}

/**
 * Mark a train as stuck and stop it if it isn't stopped right now.
 * @param v %Train to mark as being stuck.
 */
static void MarkTrainAsStuck(Train *v)
{
        if (!HasBit(v->flags, VRF_TRAIN_STUCK)) {
                /* It is the first time the problem occurred, set the "train stuck" flag. */
                SetBit(v->flags, VRF_TRAIN_STUCK);

                v->wait_counter = 0;

                /* Stop train */
                v->cur_speed = 0;
                v->subspeed = 0;
                v->SetLastSpeed();

                SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
        }
}

/**
 * Swap the two up/down flags in two ways:
 * - Swap values of \a swap_flag1 and \a swap_flag2, and
 * - If going up previously (#GVF_GOINGUP_BIT set), the #GVF_GOINGDOWN_BIT is set, and vice versa.
 * @param swap_flag1 [inout] First train flag.
 * @param swap_flag2 [inout] Second train flag.
 */
static void SwapTrainFlags(uint16 *swap_flag1, uint16 *swap_flag2)
{
        uint16 flag1 = *swap_flag1;
        uint16 flag2 = *swap_flag2;

        /* Clear the flags */
        ClrBit(*swap_flag1, GVF_GOINGUP_BIT);
        ClrBit(*swap_flag1, GVF_GOINGDOWN_BIT);
        ClrBit(*swap_flag2, GVF_GOINGUP_BIT);
        ClrBit(*swap_flag2, GVF_GOINGDOWN_BIT);

        /* Reverse the rail-flags (if needed) */
        if (HasBit(flag1, GVF_GOINGUP_BIT)) {
                SetBit(*swap_flag2, GVF_GOINGDOWN_BIT);
        } else if (HasBit(flag1, GVF_GOINGDOWN_BIT)) {
                SetBit(*swap_flag2, GVF_GOINGUP_BIT);
        }
        if (HasBit(flag2, GVF_GOINGUP_BIT)) {
                SetBit(*swap_flag1, GVF_GOINGDOWN_BIT);
        } else if (HasBit(flag2, GVF_GOINGDOWN_BIT)) {
                SetBit(*swap_flag1, GVF_GOINGUP_BIT);
        }
}

/**
 * Updates some variables after swapping the vehicle.
 * @param v swapped vehicle
 */
static void UpdateStatusAfterSwap(Train *v)
{
        /* Reverse the direction. */
        if (v->trackdir != TRACKDIR_DEPOT) v->direction = ReverseDir(v->direction);

        if (v->trackdir < TRACKDIR_END) v->trackdir = ReverseTrackdir(v->trackdir);

        /* Call the proper EnterTile function unless we are in a wormhole. */
        if (v->trackdir != TRACKDIR_WORMHOLE) {
                TrainEnterTile(v, v->tile, v->x_pos, v->y_pos);
        } else {
                assert(v->direction == DiagDirToDir(GetTunnelBridgeDirection(v->tile)));
                v->tile = GetOtherTunnelBridgeEnd(v->tile);
        }

        v->UpdatePosition();
        v->UpdateViewport(true, true);
}

/**
 * Swap vehicles \a l and \a r in consist \a v, and reverse their direction.
 * @param v Consist to change.
 * @param l %Vehicle index in the consist of the first vehicle.
 * @param r %Vehicle index in the consist of the second vehicle.
 */
void ReverseTrainSwapVeh(Train *v, int l, int r)
{
        Train *a, *b;

        /* locate vehicles to swap */
        for (a = v; l != 0; l--) a = a->Next();
        for (b = v; r != 0; r--) b = b->Next();

        if (a != b) {
                /* swap the hidden bits */
                {
                        uint16 tmp = (a->vehstatus & ~VS_HIDDEN) | (b->vehstatus & VS_HIDDEN);
                        b->vehstatus = (b->vehstatus & ~VS_HIDDEN) | (a->vehstatus & VS_HIDDEN);
                        a->vehstatus = tmp;
                }

                Swap(a->trackdir, b->trackdir);
                Swap(a->direction, b->direction);
                Swap(a->x_pos, b->x_pos);
                Swap(a->y_pos, b->y_pos);
                Swap(a->tile,  b->tile);
                Swap(a->z_pos, b->z_pos);

                SwapTrainFlags(&a->gv_flags, &b->gv_flags);

                UpdateStatusAfterSwap(a);
                UpdateStatusAfterSwap(b);
        } else {
                /* Swap GVF_GOINGUP_BIT/GVF_GOINGDOWN_BIT.
                 * This is a little bit redundant way, a->gv_flags will
                 * be (re)set twice, but it reduces code duplication */
                SwapTrainFlags(&a->gv_flags, &a->gv_flags);
                UpdateStatusAfterSwap(a);
        }
}


/**
 * Check if there is a train on a tile
 * @param tile the tile to check
 * @return true if a train is on the tile
 */
static bool TrainOnTile (TileIndex tile)
{
        VehicleTileFinder iter (tile);
        while (!iter.finished()) {
                Vehicle *v = iter.next();
                if (v->type == VEH_TRAIN) iter.set_found();
        }
        return iter.was_found();
}

/**
 * Checks whether a train is approaching a rail-road crossing from a neighbour tile
 * @param tile the crossing tile
 * @param from the neighbour tile
 * @return true if a train is approaching the crossing
 */
static bool TrainApproachingCrossingFrom (TileIndex tile, TileIndex from)
{
        VehicleTileFinder iter (from);
        while (!iter.finished()) {
                Vehicle *v = iter.next();
                if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) continue;

                Train *t = Train::From(v);
                if (t->IsFrontEngine() && TrainApproachingCrossingTile(t) == tile) iter.set_found();
        }
        return iter.was_found();
}

/**
 * Finds a vehicle approaching rail-road crossing
 * @param tile tile to test
 * @return true if a vehicle is approaching the crossing
 * @pre tile is a rail-road crossing
 */
static bool TrainApproachingCrossing(TileIndex tile)
{
        assert(IsLevelCrossingTile(tile));

        TileIndexDiff delta = TileOffsByDiagDir(AxisToDiagDir(GetCrossingRailAxis(tile)));
        return  TrainApproachingCrossingFrom (tile, tile + delta) ||
                TrainApproachingCrossingFrom (tile, tile - delta);
}


/**
 * Sets correct crossing state
 * @param tile tile to update
 * @param sound should we play sound?
 * @pre tile is a rail-road crossing
 */
void UpdateLevelCrossing(TileIndex tile, bool sound)
{
        assert(IsLevelCrossingTile(tile));

        /* reserved || train on crossing || train approaching crossing */
        bool new_state = HasCrossingReservation(tile) || TrainOnTile(tile) || TrainApproachingCrossing(tile);

        if (new_state != IsCrossingBarred(tile)) {
                if (new_state && sound) {
                        if (_settings_client.sound.ambient) SndPlayTileFx(SND_0E_LEVEL_CROSSING, tile);
                }
                SetCrossingBarred(tile, new_state);
                MarkTileDirtyByTile(tile);
        }
}


/**
 * Bars crossing and plays ding-ding sound if not barred already
 * @param tile tile with crossing
 * @pre tile is a rail-road crossing
 */
static inline void MaybeBarCrossingWithSound(TileIndex tile)
{
        if (!IsCrossingBarred(tile)) {
                BarCrossing(tile);
                if (_settings_client.sound.ambient) SndPlayTileFx(SND_0E_LEVEL_CROSSING, tile);
                MarkTileDirtyByTile(tile);
        }
}


/**
 * Advances wagons for train reversing, needed for variable length wagons.
 * This one is called before the train is reversed.
 * @param v First vehicle in chain
 */
static void AdvanceWagonsBeforeSwap(Train *v)
{
        Train *base = v;
        Train *first = base; // first vehicle to move
        Train *last = v->Last(); // last vehicle to move
        uint length = CountVehiclesInChain(v);

        while (length > 2) {
                last = last->Previous();
                first = first->Next();

                int differential = base->CalcNextVehicleOffset() - last->CalcNextVehicleOffset();

                /* do not update images now
                 * negative differential will be handled in AdvanceWagonsAfterSwap() */
                for (int i = 0; i < differential; i++) TrainController(first, last->Next());

                base = first; // == base->Next()
                length -= 2;
        }
}


/**
 * Advances wagons for train reversing, needed for variable length wagons.
 * This one is called after the train is reversed.
 * @param v First vehicle in chain
 */
static void AdvanceWagonsAfterSwap(Train *v)
{
        /* first of all, fix the situation when the train was entering a depot */
        Train *dep = v; // last vehicle in front of just left depot
        while (dep->Next() != NULL && (dep->trackdir == TRACKDIR_DEPOT || dep->Next()->trackdir != TRACKDIR_DEPOT)) {
                dep = dep->Next(); // find first vehicle outside of a depot, with next vehicle inside a depot
        }

        Train *leave = dep->Next(); // first vehicle in a depot we are leaving now

        if (leave != NULL) {
                /* 'pull' next wagon out of the depot, so we won't miss it (it could stay in depot forever) */
                int d = TicksToLeaveDepot(dep);

                if (d <= 0) {
                        leave->vehstatus &= ~VS_HIDDEN; // move it out of the depot
                        leave->trackdir = DiagDirToDiagTrackdir(GetGroundDepotDirection(leave->tile));
                        for (int i = 0; i >= d; i--) TrainController(leave, NULL); // maybe move it, and maybe let another wagon leave
                }
        } else {
                dep = NULL; // no vehicle in a depot, so no vehicle leaving a depot
        }

        Train *base = v;
        Train *first = base; // first vehicle to move
        Train *last = v->Last(); // last vehicle to move
        uint length = CountVehiclesInChain(v);

        /* We have to make sure all wagons that leave a depot because of train reversing are moved correctly
         * they have already correct spacing, so we have to make sure they are moved how they should */
        bool nomove = (dep == NULL); // If there is no vehicle leaving a depot, limit the number of wagons moved immediately.

        while (length > 2) {
                /* we reached vehicle (originally) in front of a depot, stop now
                 * (we would move wagons that are already moved with new wagon length). */
                if (base == dep) break;

                /* the last wagon was that one leaving a depot, so do not move it anymore */
                if (last == dep) nomove = true;

                last = last->Previous();
                first = first->Next();

                int differential = last->CalcNextVehicleOffset() - base->CalcNextVehicleOffset();

                /* do not update images now */
                for (int i = 0; i < differential; i++) TrainController(first, (nomove ? last->Next() : NULL));

                base = first; // == base->Next()
                length -= 2;
        }
}

/**
 * Turn a train around.
 * @param v %Train to turn around.
 */
void ReverseTrainDirection(Train *v)
{
        if (IsRailDepotTile(v->tile)) {
                InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
        }

        /* Clear path reservation in front if train is not stuck. */
        if (!HasBit(v->flags, VRF_TRAIN_STUCK)) FreeTrainTrackReservation(v);

        /* Check if we were approaching a rail/road-crossing */
        TileIndex crossing = TrainApproachingCrossingTile(v);

        /* count number of vehicles */
        int r = CountVehiclesInChain(v) - 1;  // number of vehicles - 1

        AdvanceWagonsBeforeSwap(v);

        /* swap start<>end, start+1<>end-1, ... */
        int l = 0;
        do {
                ReverseTrainSwapVeh(v, l++, r--);
        } while (l <= r);

        AdvanceWagonsAfterSwap(v);

        if (IsRailDepotTile(v->tile)) {
                InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
        }

        ToggleBit(v->flags, VRF_TOGGLE_REVERSE);

        ClrBit(v->flags, VRF_REVERSING);

        /* recalculate cached data */
        v->ConsistChanged(CCF_TRACK);

        /* update all images */
        for (Train *u = v; u != NULL; u = u->Next()) u->UpdateViewport(false, false);

        /* update crossing we were approaching */
        if (crossing != INVALID_TILE) UpdateLevelCrossing(crossing);

        /* maybe we are approaching crossing now, after reversal */
        crossing = TrainApproachingCrossingTile(v);
        if (crossing != INVALID_TILE) MaybeBarCrossingWithSound(crossing);

        /* If we are inside a depot after reversing, don't bother with path reserving. */
        if (v->trackdir == TRACKDIR_DEPOT) {
                /* Can't be stuck here as inside a depot is always a safe tile. */
                if (HasBit(v->flags, VRF_TRAIN_STUCK)) SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                ClrBit(v->flags, VRF_TRAIN_STUCK);
                return;
        }

        assert(IsSignalBufferEmpty());
        AddPosToSignalBuffer(v->GetPos(), v->owner);

        if (UpdateSignalsInBuffer() == SIGSEG_PBS || _settings_game.pf.reserve_paths) {
                RailPathPos pos = v->GetPos();

                /* If we are currently on a tile with conventional signals, we can't treat the
                 * current tile as a safe tile or we would enter a PBS block without a reservation. */
                bool first_tile_okay = !(pos.has_signal_along() &&
                        !IsPbsSignal(pos.get_signal_type()));

                /* If we are on a depot tile facing outwards, do not treat the current tile as safe. */
                if (!pos.in_wormhole() && IsRailDepotTile(pos.tile) && TrackdirToExitdir(pos.td) == GetGroundDepotDirection(pos.tile)) first_tile_okay = false;

                if (!pos.in_wormhole() && IsRailStationTile(pos.tile)) SetRailStationPlatformReservation(pos, true);
                if (TryPathReserve(v, false, first_tile_okay)) {
                        /* Do a look-ahead now in case our current tile was already a safe tile. */
                        CheckNextTrainTile(v);
                } else if (v->current_order.GetType() != OT_LOADING) {
                        /* Do not wait for a way out when we're still loading */
                        MarkTrainAsStuck(v);
                }
        } else if (HasBit(v->flags, VRF_TRAIN_STUCK)) {
                /* A train not inside a PBS block can't be stuck. */
                ClrBit(v->flags, VRF_TRAIN_STUCK);
                v->wait_counter = 0;
        }
}

/**
 * Reverse train.
 * @param tile unused
 * @param flags type of operation
 * @param p1 train to reverse
 * @param p2 if true, reverse a unit in a train (needs to be in a depot)
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdReverseTrainDirection(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        Train *v = Train::GetIfValid(p1);
        if (v == NULL) return CMD_ERROR;

        CommandCost ret = CheckOwnership(v->owner);
        if (ret.Failed()) return ret;

        if (p2 != 0) {
                /* turn a single unit around */

                if (v->IsMultiheaded() || HasBit(EngInfo(v->engine_type)->callback_mask, CBM_VEHICLE_ARTIC_ENGINE)) {
                        return_cmd_error(STR_ERROR_CAN_T_REVERSE_DIRECTION_RAIL_VEHICLE_MULTIPLE_UNITS);
                }
                if (!HasBit(EngInfo(v->engine_type)->misc_flags, EF_RAIL_FLIPS)) return CMD_ERROR;

                Train *front = v->First();
                /* make sure the vehicle is stopped in the depot */
                if (!front->IsStoppedInDepot()) {
                        return_cmd_error(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);
                }

                if (flags & DC_EXEC) {
                        ToggleBit(v->flags, VRF_REVERSE_DIRECTION);

                        front->ConsistChanged(CCF_ARRANGE);
                        SetWindowDirty(WC_VEHICLE_DEPOT, front->tile);
                        SetWindowDirty(WC_VEHICLE_DETAILS, front->index);
                        SetWindowDirty(WC_VEHICLE_VIEW, front->index);
                        SetWindowClassesDirty(WC_TRAINS_LIST);
                }
        } else {
                /* turn the whole train around */
                if ((v->vehstatus & VS_CRASHED) || v->breakdown_ctr != 0) return CMD_ERROR;

                if (flags & DC_EXEC) {
                        /* Properly leave the station if we are loading and won't be loading anymore */
                        if (v->current_order.IsType(OT_LOADING)) {
                                const Vehicle *last = v;
                                while (last->Next() != NULL) last = last->Next();

                                /* not a station || different station --> leave the station */
                                if (!IsStationTile(last->tile) || GetStationIndex(last->tile) != GetStationIndex(v->tile)) {
                                        v->LeaveStation();
                                }
                        }

                        /* We cancel any 'skip signal at dangers' here */
                        v->force_proceed = TFP_NONE;
                        SetWindowDirty(WC_VEHICLE_VIEW, v->index);

                        if (_settings_game.vehicle.train_acceleration_model != AM_ORIGINAL && v->cur_speed != 0) {
                                ToggleBit(v->flags, VRF_REVERSING);
                        } else {
                                v->cur_speed = 0;
                                v->SetLastSpeed();
                                HideFillingPercent(&v->fill_percent_te_id);
                                ReverseTrainDirection(v);
                        }
                }
        }
        return CommandCost();
}

/**
 * Force a train through a red signal
 * @param tile unused
 * @param flags type of operation
 * @param p1 train to ignore the red signal
 * @param p2 unused
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdForceTrainProceed(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        Train *t = Train::GetIfValid(p1);
        if (t == NULL) return CMD_ERROR;

        if (!t->IsPrimaryVehicle()) return CMD_ERROR;

        CommandCost ret = CheckOwnership(t->owner);
        if (ret.Failed()) return ret;


        if (flags & DC_EXEC) {
                /* If we are forced to proceed, cancel that order.
                 * If we are marked stuck we would want to force the train
                 * to proceed to the next signal. In the other cases we
                 * would like to pass the signal at danger and run till the
                 * next signal we encounter. */
                t->force_proceed = t->force_proceed == TFP_SIGNAL ? TFP_NONE : HasBit(t->flags, VRF_TRAIN_STUCK) || t->IsChainInDepot() ? TFP_STUCK : TFP_SIGNAL;
                SetWindowDirty(WC_VEHICLE_VIEW, t->index);
        }

        return CommandCost();
}

/**
 * Try to find a depot.
 * @param v %Train that wants a depot.
 * @param nearby Only consider nearby depots.
 * @param res Pointer to store information where the closest train depot is located.
 * @return Whether a depot was found.
 * @pre The given vehicle must not be crashed!
 */
static bool FindClosestTrainDepot(Train *v, bool nearby, FindDepotData *res)
{
        assert(!(v->vehstatus & VS_CRASHED));

        if (IsRailDepotTile(v->tile) && v->trackdir != DiagDirToDiagTrackdir(GetGroundDepotDirection(v->tile))) {
                *res = FindDepotData(v->tile);
                return true;
        }

        RailPathPos origin;
        FollowTrainReservation(v, &origin);
        if (IsRailDepotTile(origin.tile) && origin.td != DiagDirToDiagTrackdir(GetGroundDepotDirection(origin.tile))) {
                *res = FindDepotData(origin.tile);
                return true;
        }

        return YapfTrainFindNearestDepot (v, origin,
                nearby ? _settings_game.pf.yapf.maximum_go_to_depot_penalty : 0, res);
}

/**
 * Locate the closest depot for this consist, and return the information to the caller.
 * @param location [out]    If not \c NULL and a depot is found, store its location in the given address.
 * @param destination [out] If not \c NULL and a depot is found, store its index in the given address.
 * @param reverse [out]     If not \c NULL and a depot is found, store reversal information in the given address.
 * @return A depot has been found.
 */
bool Train::FindClosestDepot(TileIndex *location, DestinationID *destination, bool *reverse)
{
        FindDepotData tfdd;
        if (!FindClosestTrainDepot(this, false, &tfdd)) return false;

        if (location    != NULL) *location    = tfdd.tile;
        if (destination != NULL) *destination = GetDepotIndex(tfdd.tile);
        if (reverse     != NULL) *reverse     = tfdd.reverse;

        return true;
}

/** Play a sound for a train leaving the station. */
void Train::PlayLeaveStationSound() const
{
        static const SoundFx sfx[] = {
                SND_04_TRAIN,
                SND_0A_TRAIN_HORN,
                SND_0A_TRAIN_HORN,
                SND_47_MAGLEV_2,
                SND_41_MAGLEV
        };

        if (PlayVehicleSound(this, VSE_START)) return;

        EngineID engtype = this->engine_type;
        SndPlayVehicleFx(sfx[RailVehInfo(engtype)->engclass], this);
}

/**
 * Check if the train is on the last reserved tile and try to extend the path then.
 * @param v %Train that needs its path extended.
 */
static void CheckNextTrainTile(Train *v)
{
        /* Don't do any look-ahead if path_backoff_interval is 255. */
        if (_settings_game.pf.path_backoff_interval == 255) return;

        /* Exit if we are inside a depot. */
        if (v->trackdir == TRACKDIR_DEPOT) return;

        switch (v->current_order.GetType()) {
                /* Exit if we reached our destination depot. */
                case OT_GOTO_DEPOT:
                        if (v->tile == v->dest_tile) return;
                        break;

                case OT_GOTO_WAYPOINT:
                        /* If we reached our waypoint, make sure we see that. */
                        if (IsRailWaypointTile(v->tile) && GetStationIndex(v->tile) == v->current_order.GetDestination()) ProcessOrders(v);
                        break;

                case OT_NOTHING:
                case OT_LEAVESTATION:
                case OT_LOADING:
                        /* Exit if the current order doesn't have a destination, but the train has orders. */
                        if (v->GetNumOrders() > 0) return;
                        break;

                default:
                        break;
        }
        /* Exit if we are on a station tile and are going to stop. */
        if (IsRailStationTile(v->tile) && v->current_order.ShouldStopAtStation(v, GetStationIndex(v->tile))) return;

        RailPathPos pos = v->GetPos();

        /* On a tile with a red non-pbs signal, don't look ahead. */
        if (pos.has_signal_along() &&
                        !IsPbsSignal(pos.get_signal_type()) &&
                        pos.get_signal_state() == SIGNAL_STATE_RED) return;

        CFollowTrackRail ft(v, !_settings_game.pf.forbid_90_deg);
        if (ft.Follow (pos) != CFollowTrackRail::EC_NONE) return;

        if (ft.m_new.is_single() && ft.m_new.has_signal_along() &&
                        IsPbsSignal(ft.m_new.get_signal_type()) &&
                        !HasReservedPos(ft.m_new)) {
                /* If the next tile is a PBS signal, try to make a reservation. */
                ChooseTrainTrack (v, pos, ft.m_new, false);
        }
}

/**
 * Train entirely entered the depot, update its status, orders, vehicle windows, service it, etc.
 * @param v Train that entered a depot.
 */
static void TrainEnterDepot (Train *v)
{
        SetWindowClassesDirty (WC_TRAINS_LIST);
        /* Clear path reservation */
        SetDepotReservation (v->tile, false);
        if (_settings_client.gui.show_track_reservation) MarkTileDirtyByTile (v->tile);

        assert (IsSignalBufferEmpty());
        AddDepotToSignalBuffer (v->tile, v->owner);
        UpdateSignalsInBuffer();
        v->wait_counter = 0;
        v->force_proceed = TFP_NONE;
        ClrBit(v->flags, VRF_TOGGLE_REVERSE);
        v->ConsistChanged (CCF_ARRANGE);

        VehicleEnterDepot (v);
}

/**
 * Will the train stay in the depot the next tick?
 * @param v %Train to check.
 * @return True if it stays in the depot, false otherwise.
 */
static bool CheckTrainStayInDepot(Train *v)
{
        /* bail out if not all wagons are in the same depot or not in a depot at all */
        for (const Train *u = v; u != NULL; u = u->Next()) {
                if (u->trackdir != TRACKDIR_DEPOT || u->tile != v->tile) return false;
        }

        /* if the train got no power, then keep it in the depot */
        if (v->gcache.cached_power == 0) {
                v->vehstatus |= VS_STOPPED;
                SetWindowDirty(WC_VEHICLE_DEPOT, v->tile);
                return true;
        }

        bool try_reserve;

        if (v->force_proceed == TFP_NONE) {
                /* force proceed was not pressed */
                if (++v->wait_counter < 37) {
                        SetWindowClassesDirty(WC_TRAINS_LIST);
                        return true;
                }

                v->wait_counter = 0;

                if (HasDepotReservation(v->tile)) {
                        /* Depot reserved, can't exit. */
                        SetWindowClassesDirty(WC_TRAINS_LIST);
                        return true;
                }

                if (_settings_game.pf.reserve_paths) {
                        try_reserve = true;
                } else {
                        assert(IsSignalBufferEmpty());
                        AddDepotToSignalBuffer(v->tile, v->owner);
                        SigSegState seg_state = UpdateSignalsInBuffer();
                        if (seg_state == SIGSEG_FULL) {
                                /* Full and no PBS signal in block, can't exit. */
                                SetWindowClassesDirty(WC_TRAINS_LIST);
                                return true;
                        }
                        try_reserve = seg_state == SIGSEG_PBS;
                }
        } else if (_settings_game.pf.reserve_paths) {
                try_reserve = true;
        } else {
                assert(IsSignalBufferEmpty());
                AddDepotToSignalBuffer(v->tile, v->owner);
                try_reserve = UpdateSignalsInBuffer() == SIGSEG_PBS;
        }

        /* We are leaving a depot, but have to go to the exact same one; re-enter */
        if (v->current_order.IsType(OT_GOTO_DEPOT) && v->tile == v->dest_tile) {
                /* We need to have a reservation for this to work. */
                if (HasDepotReservation(v->tile)) return true;
                SetDepotReservation(v->tile, true);
                TrainEnterDepot (v);
                return true;
        }

        /* Only leave when we can reserve a path to our destination. */
        if (try_reserve) {
                if (HasDepotReservation (v->tile) || !TryPathExtend (v, v->GetPos())) {
                        /* Failed to get a reservation. */
                        if (v->force_proceed == TFP_NONE) {
                                /* No path and no force proceed. */
                                SetWindowClassesDirty(WC_TRAINS_LIST);
                                MarkTrainAsStuck(v);
                                return true;
                        }
                }
        }

        SetDepotReservation(v->tile, true);
        if (_settings_client.gui.show_track_reservation) MarkTileDirtyByTile(v->tile);

        VehicleServiceInDepot(v);
        SetWindowClassesDirty(WC_TRAINS_LIST);
        v->PlayLeaveStationSound();

        v->trackdir = DiagDirToDiagTrackdir(DirToDiagDir(v->direction));

        v->vehstatus &= ~VS_HIDDEN;
        v->cur_speed = 0;

        v->UpdateViewport(true, true);
        v->UpdatePosition();

        assert(IsSignalBufferEmpty());
        AddDepotToSignalBuffer(v->tile, v->owner);
        UpdateSignalsInBuffer();

        v->UpdateAcceleration();
        InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);

        return false;
}

/**
 * Clear the reservation of \a tile that was just left by a wagon on \a track_dir.
 * @param pos position to clear.
 */
static void ClearPathReservation (const RailPathPos &pos)
{
        DiagDirection dir = TrackdirToExitdir(pos.td);

        if (pos.in_wormhole()) {
                UnreserveRailTrack(pos);
        } else if (IsRailStationTile(pos.tile)) {
                TileIndex new_tile = TileAddByDiagDir(pos.tile, dir);
                /* If the new tile is not a further tile of the same station, we
                 * clear the reservation for the whole platform. */
                if (!IsCompatibleTrainStationTile(new_tile, pos.tile)) {
                        SetRailStationPlatformReservation(pos.tile, ReverseDiagDir(dir), false);
                }
        } else {
                /* Any other tile */
                UnreserveRailTrack(pos);
        }
}

/**
 * Free the reserved path in front of a vehicle.
 * @param v %Train owning the reserved path.
 * @param end Position where the reservation ends
 */
static void FreeTrainTrackReservation (const Train *v, const RailPathPos *end)
{
        assert(v->IsFrontEngine());

        RailPathPos pos = v->GetPos();
        assert (!IsRailDepotTile(pos.tile) || TrackdirToExitdir(pos.td) == GetGroundDepotDirection(pos.tile));

        /* Don't free reservation if it's not ours. */
        if (!pos.in_wormhole() && TracksOverlap(GetReservedTrackbits(pos.tile) | TrackToTrackBits(TrackdirToTrack(pos.td)))) return;

        CFollowTrackRail ft(v, true, v->railtype);
        ft.SetPos(pos);

        bool first = true;
        for (;;) {
                if (end != NULL && ft.m_new == *end) return;

                if (ft.FollowNext() != CFollowTrackRail::EC_NONE) break;

                if (!ft.m_new.in_wormhole()) {
                        TrackdirBits trackdirs = ft.m_new.trackdirs & TrackBitsToTrackdirBits(GetReservedTrackbits(ft.m_new.tile));
                        if (trackdirs == TRACKDIR_BIT_NONE) break;
                        ft.m_new.set_trackdirs (trackdirs);
                        assert(ft.m_new.is_single());
                }

                if (ft.m_new.has_signal_along()) {
                        if (!IsPbsSignal(ft.m_new.get_signal_type())) {
                                /* Conventional signal along trackdir: remove reservation and stop. */
                                UnreserveRailTrack(ft.m_new);
                                break;
                        } else if (ft.m_new.get_signal_state() == SIGNAL_STATE_RED) {
                                /* Red PBS signal? Can't be our reservation, would be green then. */
                                break;
                        } else {
                                /* Turn the signal back to red. */
                                ft.m_new.set_signal_state (SIGNAL_STATE_RED);
                                MarkTileDirtyByTile(ft.m_new.tile);
                        }
                } else if (ft.m_new.has_signal_against() && IsOnewaySignal(ft.m_new.get_signal_type())) {
                        break;
                }

                if (first) {
                        if (ft.m_flag == ft.TF_BRIDGE) {
                                assert(IsRailBridgeTile(ft.m_old.in_wormhole() ? ft.m_old.wormhole : ft.m_old.tile));
                        } else if (ft.m_flag == ft.TF_TUNNEL) {
                                assert(IsTunnelTile(ft.m_old.in_wormhole() ? ft.m_old.wormhole : ft.m_old.tile));
                        }
                }

                /* Don't free first station if we are on it. */
                if (!first || (ft.m_flag != ft.TF_STATION) ||
                                !IsRailStationTile(ft.m_old.tile) || GetStationIndex(ft.m_new.tile) != GetStationIndex(ft.m_old.tile)) {
                        ClearPathReservation (ft.m_new);
                }

                first = false;
        }

        /* If we were given an ending position but did not find it, then
         * something is wrong. */
        assert (end == NULL);
}

/**
 * Free the reserved path in front of a vehicle, if any.
 * @param v %Train owning the reserved path.
 * @return Whether the train had a reservation (not in or entering a depot)
 */
bool FreeTrainTrackReservation (const Train *v)
{
        assert(v->IsFrontEngine());

        /* Can't be holding a reservation if we enter a depot. */
        if (v->trackdir == TRACKDIR_DEPOT) return false;
        if (IsRailDepotTile (v->tile) && v->trackdir != DiagDirToDiagTrackdir (GetGroundDepotDirection (v->tile))) return false;

        FreeTrainTrackReservation (v, NULL);
        return true;
}

/**
 * Perform pathfinding for a train.
 *
 * @param v The train
 * @param origin The end of the current reservation
 * @param do_track_reservation Path reservation is requested
 * @param dest [out] State and destination of the requested path
 * @return The best trackdir the train should follow
 */
static Trackdir DoTrainPathfind(const Train *v, const RailPathPos &origin, bool do_track_reservation, PFResult *dest)
{
        return YapfTrainChooseTrack(v, origin, do_track_reservation, dest);
}

/**
 * Return value type for ExtendTrainReservation
 */
enum ExtendReservationResult {
        EXTEND_RESERVATION_SAFE,   ///< Reservation extended to a safe tile
        EXTEND_RESERVATION_UNSAFE, ///< Reservation extended to an unsafe tile
        EXTEND_RESERVATION_FAILED, ///< Reservation could not be extended
};

/**
 * Extend a train path as far as possible. Stops on encountering a safe tile,
 * another reservation or a track choice.
 * @param v The train whose reservation to extend
 * @param origin The end of the current reservation, which will be updated
 * @return An ExtendReservationResult value, showing reservation extension outcome
 */
static ExtendReservationResult ExtendTrainReservation(const Train *v, RailPathPos *origin)
{
        CFollowTrackRail ft(v, !_settings_game.pf.forbid_90_deg);
        ft.SetPos(*origin);

        for (;;) {
                CFollowTrackRail::ErrorCode err = ft.FollowNext();
                if (err == CFollowTrackRail::EC_NO_WAY) {
                        /* End of line, path valid and okay. */
                        *origin = ft.m_old;
                        return EXTEND_RESERVATION_SAFE;
                } else if (err != CFollowTrackRail::EC_NONE) {
                        break;
                }

                /* A depot is always a safe waiting position. */
                if (!ft.m_new.in_wormhole() && IsRailDepotTile(ft.m_new.tile)) {
                        /* Depot must be free for reservation to continue. */
                        if (HasDepotReservation(ft.m_new.tile)) break;

                        SetDepotReservation(ft.m_new.tile, true);
                        *origin = ft.m_new;
                        return EXTEND_RESERVATION_SAFE;
                }

                /* Station and waypoints are possible targets. */
                if (ft.m_flag == ft.TF_STATION) {
                        /* Possible target encountered.
                         * On finding a possible target, we need to stop and let the pathfinder handle the
                         * remaining path. This is because we don't know if this target is in one of our
                         * orders, so we might cause pathfinding to fail later on if we find a choice.
                         * This failure would cause a bogous call to TryReserveSafePath which might reserve
                         * a wrong path not leading to our next destination. */
                        if (!ft.MaskReservedTracks()) break;

                        /* If we did skip some tiles, backtrack to the first skipped tile so the pathfinder
                         * actually starts its search at the first unreserved tile. */
                        ft.m_new.tile -= TileOffsByDiagDir(ft.m_exitdir) * ft.m_tiles_skipped;

                        /* Possible target found, path valid but not okay. */
                        *origin = ft.m_old;
                        return EXTEND_RESERVATION_UNSAFE;
                }

                if (!ft.m_new.is_single()) {
                        /* Choice found. */
                        if (HasReservedTracks(ft.m_new.tile, TrackdirBitsToTrackBits(ft.m_new.trackdirs))) break;

                        assert(ft.m_tiles_skipped == 0);

                        /* Choice found, path valid but not okay. Save info about the choice tile as well. */
                        *origin = ft.m_old;
                        return EXTEND_RESERVATION_UNSAFE;
                }

                /* Possible signal tile. */
                if (ft.m_new.has_blocking_signal()) break;

                PBSPositionState state = CheckWaitingPosition(v, ft.m_new, _settings_game.pf.forbid_90_deg);
                if (state == PBS_BUSY) break;

                if (!TryReserveRailTrack(ft.m_new)) break;

                if (state == PBS_FREE) {
                        /* Safe position is all good, path valid and okay. */
                        *origin = ft.m_new;
                        return EXTEND_RESERVATION_SAFE;
                }
        }

        /* Sorry, can't reserve path, back out. */
        RailPathPos stopped = ft.m_old;
        ft.SetPos(*origin);
        while (ft.m_new != stopped) {
                if (ft.FollowNext() != CFollowTrackRail::EC_NONE) NOT_REACHED();

                assert(!ft.m_new.is_empty());
                assert(ft.m_new.is_single());

                UnreserveRailTrack(ft.m_new);
        }

        /* Path invalid. */
        return EXTEND_RESERVATION_FAILED;
}

/**
 * Try to reserve any path to a safe tile, ignoring the vehicle's destination.
 * Safe tiles are tiles in front of a signal, depots and station tiles at end of line.
 *
 * @param v The vehicle.
 * @param pos The position the search should start from.
 * @param override_railtype Whether all physically compatible railtypes should be followed.
 * @return True if a path to a safe stopping tile could be reserved.
 */
static bool TryReserveSafeTrack(const Train *v, const RailPathPos &pos, bool override_tailtype)
{
        return YapfTrainFindNearestSafeTile(v, pos, override_tailtype);
}

/** This class will save the current order of a vehicle and restore it on destruction. */
class VehicleOrderSaver {
private:
        Train          *v;
        BaseOrder      old_order;
        TileIndex      old_dest_tile;
        StationID      old_last_station_visited;
        VehicleOrderID index;
        bool           suppress_implicit_orders;

public:
        VehicleOrderSaver(Train *_v) :
                v(_v),
                old_order(_v->current_order),
                old_dest_tile(_v->dest_tile),
                old_last_station_visited(_v->last_station_visited),
                index(_v->cur_real_order_index),
                suppress_implicit_orders(HasBit(_v->gv_flags, GVF_SUPPRESS_IMPLICIT_ORDERS))
        {
        }

        ~VehicleOrderSaver()
        {
                this->v->current_order = this->old_order;
                this->v->dest_tile = this->old_dest_tile;
                this->v->last_station_visited = this->old_last_station_visited;
                SB(this->v->gv_flags, GVF_SUPPRESS_IMPLICIT_ORDERS, 1, suppress_implicit_orders ? 1: 0);
        }

        /**
         * Set the current vehicle order to the next order in the order list.
         * @param skip_first Shall the first (i.e. active) order be skipped?
         * @return True if a suitable next order could be found.
         */
        bool SwitchToNextOrder(bool skip_first)
        {
                if (this->v->GetNumOrders() == 0) return false;

                if (skip_first) ++this->index;

                int depth = 0;

                do {
                        /* Wrap around. */
                        if (this->index >= this->v->GetNumOrders()) this->index = 0;

                        Order *order = this->v->GetOrder(this->index);
                        assert(order != NULL);

                        switch (order->GetType()) {
                                case OT_GOTO_DEPOT:
                                        /* Skip service in depot orders when the train doesn't need service. */
                                        if ((order->GetDepotOrderType() & ODTFB_SERVICE) && !this->v->NeedsServicing()) break;
                                case OT_GOTO_STATION:
                                case OT_GOTO_WAYPOINT:
                                        this->v->current_order = *order;
                                        return UpdateOrderDest(this->v, order, 0, true);
                                case OT_CONDITIONAL: {
                                        VehicleOrderID next = ProcessConditionalOrder(order, this->v);
                                        if (next != INVALID_VEH_ORDER_ID) {
                                                depth++;
                                                this->index = next;
                                                /* Don't increment next, so no break here. */
                                                continue;
                                        }
                                        break;
                                }
                                default:
                                        break;
                        }
                        /* Don't increment inside the while because otherwise conditional
                         * orders can lead to an infinite loop. */
                        ++this->index;
                        depth++;
                } while (this->index != this->v->cur_real_order_index && depth < this->v->GetNumOrders());

                return false;
        }
};

/* choose a track */
static bool ChooseTrainTrack (Train *v, RailPathPos origin,
        const PathMPos<RailPathPos> &pos, bool force_res,
        Trackdir *best_trackdir)
{
        bool do_track_reservation = _settings_game.pf.reserve_paths || force_res;
        bool change_signal = false;

        assert (!pos.is_empty());

        /* Quick return in case only one possible trackdir is available */
        if (pos.is_single()) {
                if (best_trackdir != NULL) *best_trackdir = pos.td;
                /* We need to check for signals only here, as a junction tile can't have signals. */
                if (pos.has_signal_along() && IsPbsSignal (pos.get_signal_type())) {
                        do_track_reservation = true;
                        change_signal = true;
                } else if (!do_track_reservation) {
                        return true;
                }
        }

        if (do_track_reservation) {
                switch (ExtendTrainReservation(v, &origin)) {
                        default: NOT_REACHED();
                        case EXTEND_RESERVATION_FAILED:
                                if (best_trackdir != NULL) *best_trackdir = FindFirstTrackdir (pos.trackdirs);
                                return false;
                        case EXTEND_RESERVATION_SAFE:
                                assert (pos.is_single());
                                if (change_signal) {
                                        pos.set_signal_state (SIGNAL_STATE_GREEN);
                                        MarkTileDirtyByTile (pos.tile);
                                }
                                TryReserveRailTrack(v->GetPos());
                                return true;
                        case EXTEND_RESERVATION_UNSAFE:
                                break;
                }

                /* Check if the train needs service here, so it has a chance to always find a depot.
                 * Also check if the current order is a service order so we don't reserve a path to
                 * the destination but instead to the next one if service isn't needed. */
                CheckIfTrainNeedsService(v);
                if (v->current_order.IsType(OT_DUMMY) || v->current_order.IsType(OT_CONDITIONAL) || v->current_order.IsType(OT_GOTO_DEPOT)) ProcessOrders(v);
        }

        /* Save the current train order. The destructor will restore the old order on function exit. */
        VehicleOrderSaver orders(v);

        /* If the current tile is the destination of the current order and
         * a reservation was requested, advance to the next order.
         * Don't advance on a depot order as depots are always safe end points
         * for a path and no look-ahead is necessary. This also avoids a
         * problem with depot orders not part of the order list when the
         * order list itself is empty. */
        if (v->current_order.IsType(OT_LEAVESTATION)) {
                orders.SwitchToNextOrder(false);
        } else if (v->current_order.IsType(OT_LOADING) || (!v->current_order.IsType(OT_GOTO_DEPOT) && (
                        v->current_order.IsType(OT_GOTO_STATION) ?
                        IsRailStationTile(v->tile) && v->current_order.GetDestination() == GetStationIndex(v->tile) :
                        v->tile == v->dest_tile))) {
                orders.SwitchToNextOrder(true);
        }

        /* Call the pathfinder... */
        PFResult res_dest;
        Trackdir next_trackdir = DoTrainPathfind(v, origin, do_track_reservation, &res_dest);
        v->HandlePathfindingResult(res_dest.found);
        /* ...but only use the result if we were at the original tile. */
        if (best_trackdir != NULL && !pos.is_single()) {
                /* The initial tile had more than one available trackdir.
                 * This means that ExtendTrainReservation cannot possibly
                 * have extended the reservation, and we are pathfinding
                 * at the original tile. */
                *best_trackdir = next_trackdir != INVALID_TRACKDIR ? next_trackdir : FindFirstTrackdir (pos.trackdirs);
                /* If the initial tile only had one available trackdir, then
                 * *best_trackdir was set along with single_trackdir. */
        }

        /* No track reservation requested -> finished. */
        if (!do_track_reservation) {
                assert (!change_signal);
                return true;
        }

        if (change_signal) pos.set_signal_state (SIGNAL_STATE_GREEN);

        /* A path was found, but could not be reserved. */
        if (res_dest.pos.is_valid_tile() && !res_dest.okay) {
                FreeTrainTrackReservation (v, &origin);
                return false;
        }

        /* No possible reservation target found, we are probably lost. */
        if (!res_dest.pos.is_valid_tile()) {
                /* Try to find any safe destination. */
                if (TryReserveSafeTrack(v, origin, false)) {
                        if (best_trackdir != NULL && !pos.is_single()) {
                                TrackBits res = GetReservedTrackbits (pos.tile);
                                *best_trackdir = FindFirstTrackdir (TrackBitsToTrackdirBits(res) & pos.trackdirs);
                        }
                        TryReserveRailTrack(v->GetPos());
                        if (change_signal) MarkTileDirtyByTile (pos.tile);
                        return true;
                } else {
                        FreeTrainTrackReservation (v, &origin);
                        return false;
                }
        }

        /* Extend reservation until we have found a safe position. */
        bool safe = false;
        for (;;) {
                origin = res_dest.pos;
                if (IsSafeWaitingPosition(v, origin, _settings_game.pf.forbid_90_deg)) {
                        safe = true;
                        break;
                }

                /* Get next order with destination. */
                if (!orders.SwitchToNextOrder(true)) break;

                DoTrainPathfind(v, origin, true, &res_dest);
                /* Break if no safe position was found. */
                if (!res_dest.pos.is_valid_tile()) break;

                if (!res_dest.okay) {
                        /* Path found, but could not be reserved. */
                        FreeTrainTrackReservation (v, &origin);
                        return false;
                }
        }

        /* No order or no safe position found, try any position. */
        if (!safe) safe = TryReserveSafeTrack(v, origin, true);

        if (!safe) {
                FreeTrainTrackReservation (v, &origin);
        } else if (change_signal) {
                MarkTileDirtyByTile (pos.tile);
        }

        return safe;
}

/**
 * Try to extend a reserved path to a safe position.
 * @param v The vehicle.
 * @param origin Current end of the reservation.
 * @param mark_as_stuck Whether the train should be marked as stuck on a failed reservation.
 * @return Whether the reserved path could be extended.
 */
static bool TryPathExtend (Train *v, const RailPathPos &origin, bool mark_as_stuck)
{
        CFollowTrackRail ft (v, !_settings_game.pf.forbid_90_deg);

        if ((ft.Follow (origin) == CFollowTrackRail::EC_NONE)
                        && !ChooseTrainTrack (v, origin, ft.m_new, true)) {
                if (mark_as_stuck) MarkTrainAsStuck(v);
                return false;
        }

        if (HasBit (v->flags, VRF_TRAIN_STUCK)) {
                v->wait_counter = 0;
                SetWindowWidgetDirty (WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                ClrBit (v->flags, VRF_TRAIN_STUCK);
        }

        return true;
}

/**
 * Try to reserve a path to a safe position.
 *
 * @param v The vehicle
 * @param mark_as_stuck Should the train be marked as stuck on a failed reservation?
 * @param first_tile_okay True if no path should be reserved if the current tile is a safe position.
 * @return True if a path could be reserved.
 */
bool TryPathReserve(Train *v, bool mark_as_stuck, bool first_tile_okay)
{
        assert(v->IsFrontEngine());
        assert(v->trackdir != TRACKDIR_DEPOT);

        RailPathPos origin;
        /* The path we are driving on is already blocked by some other train.
         * This can only happen in certain situations when mixing path and
         * block signals or when changing tracks and/or signals.
         * Exit here as doing any further reservations will probably just
         * make matters worse. */
        if (!FollowTrainReservation (v, &origin, true)) {
                if (mark_as_stuck) MarkTrainAsStuck(v);
                return false;
        }

        /* If we have a reserved path and the path ends at a safe tile, we are finished already. */
        if ((v->tile != origin.tile || first_tile_okay) && IsSafeWaitingPosition(v, origin, _settings_game.pf.forbid_90_deg)) {
                /* Can't be stuck then. */
                if (HasBit(v->flags, VRF_TRAIN_STUCK)) SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                ClrBit(v->flags, VRF_TRAIN_STUCK);
                return true;
        }

        return TryPathExtend (v, origin, mark_as_stuck);
}


static bool CheckReverseTrain(const Train *v)
{
        if (_settings_game.difficulty.line_reverse_mode != 0 ||
                        v->trackdir == TRACKDIR_DEPOT || v->trackdir == TRACKDIR_WORMHOLE ||
                        !(v->direction & 1)) {
                return false;
        }

        assert(IsValidTrackdir(v->trackdir));

        return YapfTrainCheckReverse(v);
}

/**
 * Get the location of the next station to visit.
 * @param station Next station to visit.
 * @return Location of the new station.
 */
TileIndex Train::GetOrderStationLocation(StationID station)
{
        if (station == this->last_station_visited) this->last_station_visited = INVALID_STATION;

        const Station *st = Station::Get(station);
        if (!(st->facilities & FACIL_TRAIN)) {
                /* The destination station has no trainstation tiles. */
                this->IncrementRealOrderIndex();
                return 0;
        }

        return st->xy;
}

/** Goods at the consist have changed, update the graphics, cargo, and acceleration. */
void Train::MarkDirty()
{
        Train *v = this;
        do {
                v->colourmap = PAL_NONE;
                v->UpdateViewport(true, false);
        } while ((v = v->Next()) != NULL);

        /* need to update acceleration and cached values since the goods on the train changed. */
        this->CargoChanged();
        this->UpdateAcceleration();
}

/**
 * This function looks at the vehicle and updates its speed (cur_speed
 * and subspeed) variables. Furthermore, it returns the distance that
 * the train can drive this tick. #Vehicle::GetAdvanceDistance() determines
 * the distance to drive before moving a step on the map.
 * @return distance to drive.
 */
int Train::UpdateSpeed()
{
        switch (_settings_game.vehicle.train_acceleration_model) {
                default: NOT_REACHED();
                case AM_ORIGINAL:
                        return this->DoUpdateSpeed(this->acceleration * (this->GetAccelerationStatus() == AS_BRAKE ? -4 : 2), 0, this->GetCurrentMaxSpeed());

                case AM_REALISTIC:
                        return this->DoUpdateSpeed(this->GetAcceleration(), this->GetAccelerationStatus() == AS_BRAKE ? 0 : 2, this->GetCurrentMaxSpeed());
        }
}

/**
 * Trains enters a station, send out a news item if it is the first train, and start loading.
 * @param v Train that entered the station.
 * @param station Station visited.
 */
static void TrainEnterStation(Train *v, StationID station)
{
        v->last_station_visited = station;

        /* check if a train ever visited this station before */
        Station *st = Station::Get(station);
        if (!(st->had_vehicle_of_type & HVOT_TRAIN)) {
                st->had_vehicle_of_type |= HVOT_TRAIN;
                AddNewsItem<ArrivalNewsItem> (STR_NEWS_FIRST_TRAIN_ARRIVAL, v, st);
                AI::NewEvent(v->owner, new ScriptEventStationFirstVehicle(st->index, v->index));
                Game::NewEvent(new ScriptEventStationFirstVehicle(st->index, v->index));
        }

        v->force_proceed = TFP_NONE;
        SetWindowDirty(WC_VEHICLE_VIEW, v->index);

        v->BeginLoading();

        TriggerStationRandomisation(st, v->tile, SRT_TRAIN_ARRIVES);
        TriggerStationAnimation(st, v->tile, SAT_TRAIN_ARRIVES);
}

/* Check if the vehicle is compatible with the specified tile */
static inline bool CheckCompatibleRail(const Train *v, TileIndex tile, Track track = INVALID_TRACK)
{
        return IsTileOwner(tile, v->owner) &&
                        (!v->IsFrontEngine() || HasBit(v->compatible_railtypes, GetRailType(tile, track)));
}

/** Data structure for storing engine speed changes of an acceleration type. */
struct AccelerationSlowdownParams {
        byte small_turn; ///< Speed change due to a small turn.
        byte large_turn; ///< Speed change due to a large turn.
        byte z_up;       ///< Fraction to remove when moving up.
        byte z_down;     ///< Fraction to add when moving down.
};

/** Speed update fractions for each acceleration type. */
static const AccelerationSlowdownParams _accel_slowdown[] = {
        /* normal accel */
        {256 / 4, 256 / 2, 256 / 4, 2}, ///< normal
        {256 / 4, 256 / 2, 256 / 4, 2}, ///< monorail
        {0,       256 / 2, 256 / 4, 2}, ///< maglev
};

/**
 * Modify the speed of the vehicle due to a change in altitude.
 * @param v %Train to update.
 * @param old_z Previous height.
 */
static inline void AffectSpeedByZChange(Train *v, int old_z)
{
        if (old_z == v->z_pos || _settings_game.vehicle.train_acceleration_model != AM_ORIGINAL) return;

        const AccelerationSlowdownParams *asp = &_accel_slowdown[GetRailTypeInfo(v->railtype)->acceleration_type];

        if (old_z < v->z_pos) {
                v->cur_speed -= (v->cur_speed * asp->z_up >> 8);
        } else {
                uint16 spd = v->cur_speed + asp->z_down;
                if (spd <= v->gcache.cached_max_track_speed) v->cur_speed = spd;
        }
}

/** Tries to reserve track under whole train consist. */
void Train::ReserveTrackUnderConsist() const
{
        for (const Train *u = this; u != NULL; u = u->Next()) {
                switch (u->trackdir) {
                        case TRACKDIR_WORMHOLE:
                                if (IsRailwayTile(u->tile)) {
                                        SetBridgeMiddleReservation(u->tile, true);
                                        SetBridgeMiddleReservation(GetOtherBridgeEnd(u->tile), true);
                                } else {
                                        SetTunnelMiddleReservation(u->tile, true);
                                        SetTunnelMiddleReservation(GetOtherTunnelEnd(u->tile), true);
                                }
                                break;
                        case TRACKDIR_DEPOT:
                                break;
                        default:
                                TryReserveRailTrack(u->tile, TrackdirToTrack(u->trackdir));
                                break;
                }
        }
}

/**
 * The train vehicle crashed!
 * Update its status and other parts around it.
 * @param flooded Crash was caused by flooding.
 * @return Number of people killed.
 */
uint Train::Crash(bool flooded)
{
        uint pass = 0;
        if (this->IsFrontEngine()) {
                pass += 2; // driver

                /* Remove the reserved path in front of the train if it is not stuck.
                 * Also clear all reserved tracks the train is currently on. */
                if (!HasBit(this->flags, VRF_TRAIN_STUCK)) FreeTrainTrackReservation(this);
                for (const Train *v = this; v != NULL; v = v->Next()) {
                        ClearPathReservation (v->GetPos());
                }

                /* we may need to update crossing we were approaching,
                 * but must be updated after the train has been marked crashed */
                TileIndex crossing = TrainApproachingCrossingTile(this);
                if (crossing != INVALID_TILE) UpdateLevelCrossing(crossing);

                /* Remove the loading indicators (if any) */
                HideFillingPercent(&this->fill_percent_te_id);
        }

        pass += this->GroundVehicleBase::Crash(flooded);

        this->crash_anim_pos = flooded ? 4000 : 1; // max 4440, disappear pretty fast when flooded
        return pass;
}

/**
 * Marks train as crashed and creates an AI event.
 * Doesn't do anything if the train is crashed already.
 * @param v first vehicle of chain
 * @return number of victims (including 2 drivers; zero if train was already crashed)
 */
static uint TrainCrashed(Train *v)
{
        uint num = 0;

        /* do not crash train twice */
        if (!(v->vehstatus & VS_CRASHED)) {
                num = v->Crash();
                AI::NewEvent(v->owner, new ScriptEventVehicleCrashed(v->index, v->tile, ScriptEventVehicleCrashed::CRASH_TRAIN));
                Game::NewEvent(new ScriptEventVehicleCrashed(v->index, v->tile, ScriptEventVehicleCrashed::CRASH_TRAIN));
        }

        /* Try to re-reserve track under already crashed train too.
         * Crash() clears the reservation! */
        v->ReserveTrackUnderConsist();

        return num;
}

/**
 * Collision test function.
 * @param tcc %Train being examined.
 * @param v %Train vehicle to test collision with.
 * @return Total number of victims if train collided, else 0.
 */
static uint FindTrainCollision(Train *tcc, Vehicle *v)
{
        /* not a train or in depot */
        if (v->type != VEH_TRAIN || Train::From(v)->trackdir == TRACKDIR_DEPOT) return 0;

        /* do not crash into trains of another company. */
        if (v->owner != tcc->owner) return 0;

        /* get first vehicle now to make most usual checks faster */
        Train *coll = Train::From(v)->First();

        /* can't collide with own wagons */
        if (coll == tcc) return 0;

        int x_diff = v->x_pos - tcc->x_pos;
        int y_diff = v->y_pos - tcc->y_pos;

        /* Do fast calculation to check whether trains are not in close vicinity
         * and quickly reject trains distant enough for any collision.
         * Differences are shifted by 7, mapping range [-7 .. 8] into [0 .. 15]
         * Differences are then ORed and then we check for any higher bits */
        uint hash = (y_diff + 7) | (x_diff + 7);
        if (hash & ~15) return 0;

        /* Slower check using multiplication */
        int min_diff = (Train::From(v)->gcache.cached_veh_length + 1) / 2 + (tcc->gcache.cached_veh_length + 1) / 2 - 1;
        if (x_diff * x_diff + y_diff * y_diff > min_diff * min_diff) return 0;

        /* Happens when there is a train under bridge next to bridge head */
        if (abs(v->z_pos - tcc->z_pos) > 5) return 0;

        /* crash both trains */
        return TrainCrashed(tcc) + TrainCrashed(coll);
}

/** Temporary data storage for testing collisions. */
struct TrainCollideChecker {
        Train *v; ///< %Vehicle we are testing for collision.
        uint num; ///< Total number of victims if train collided.
};

/**
 * Collision test function.
 * @param v %Train vehicle to test collision with.
 * @param data %Train being examined.
 * @return \c NULL (always continue search)
 */
static Vehicle *FindTrainCollideEnum(Vehicle *v, void *data)
{
        TrainCollideChecker *tcc = (TrainCollideChecker*)data;

        tcc->num += FindTrainCollision (tcc->v, v);

        return NULL;
}

/**
 * Checks whether the specified train has a collision with another vehicle. If
 * so, destroys this vehicle, and the other vehicle if its subtype has TS_Front.
 * Reports the incident in a flashy news item, modifies station ratings and
 * plays a sound.
 * @param v %Train to test.
 */
static bool CheckTrainCollision(Train *v)
{
        /* can't collide in depot */
        if (v->trackdir == TRACKDIR_DEPOT) return false;

        assert(v->trackdir == TRACKDIR_WORMHOLE || TileVirtXY(v->x_pos, v->y_pos) == v->tile);

        TrainCollideChecker tcc;
        tcc.v = v;
        tcc.num = 0;

        /* find colliding vehicles */
        if (v->trackdir == TRACKDIR_WORMHOLE) {
                VehicleTileIterator iter1 (v->tile);
                while (!iter1.finished()) {
                        tcc.num += FindTrainCollision (v, iter1.next());
                }
                VehicleTileIterator iter2 (GetOtherTunnelBridgeEnd(v->tile));
                while (!iter2.finished()) {
                        tcc.num += FindTrainCollision (v, iter2.next());
                }
        } else {
                FindVehicleOnPosXY(v->x_pos, v->y_pos, &tcc, FindTrainCollideEnum);
        }

        /* any dead -> no crash */
        if (tcc.num == 0) return false;

        AddNewsItem<VehicleNewsItem> (STR_NEWS_TRAIN_CRASH, NT_ACCIDENT,
                        v->index, tcc.num);

        ModifyStationRatingAround(v->tile, v->owner, -160, 30);
        if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_13_BIG_CRASH, v);
        return true;
}


/**
 * Tile callback routine when vehicle enters a track tile
 * @see vehicle_enter_tile_proc
 */
static void TrainEnter_Track(Train *v, TileIndex tile, int x, int y)
{
        if (IsTileSubtype(tile, TT_TRACK)) return;

        assert(abs((int)(GetSlopePixelZ(x, y) - v->z_pos)) < 3);

        /* modify speed of vehicle */
        uint16 spd = GetBridgeSpec(GetRailBridgeType(tile))->speed;
        Vehicle *first = v->First();
        first->cur_speed = min(first->cur_speed, spd);
}

/**
 * Frame when the 'enter tunnel' sound should be played. This is the second
 * frame on a tile, so the sound is played shortly after entering the tunnel
 * tile, while the vehicle is still visible.
 */
static const byte TUNNEL_SOUND_FRAME = 1;

extern const byte _tunnel_visibility_frame[DIAGDIR_END];

/**
 * Compute number of ticks when next wagon will leave a depot.
 * Negative means next wagon should have left depot n ticks before.
 * @param v vehicle outside (leaving) the depot
 * @return number of ticks when the next wagon will leave
 */
int TicksToLeaveDepot(const Train *v)
{
        DiagDirection dir = GetGroundDepotDirection(v->tile);
        int length = v->CalcNextVehicleOffset();

        switch (dir) {
                case DIAGDIR_NE: return  ((int)(v->x_pos & 0x0F) - (_vehicle_initial_x_fract[dir] - (length + 1)));
                case DIAGDIR_SE: return -((int)(v->y_pos & 0x0F) - (_vehicle_initial_y_fract[dir] + (length + 1)));
                case DIAGDIR_SW: return -((int)(v->x_pos & 0x0F) - (_vehicle_initial_x_fract[dir] + (length + 1)));
                default:
                case DIAGDIR_NW: return  ((int)(v->y_pos & 0x0F) - (_vehicle_initial_y_fract[dir] - (length + 1)));
        }

        return 0; // make compilers happy
}

static void TrainEnter_Misc(Train *u, TileIndex tile, int x, int y)
{
        switch (GetTileSubtype(tile)) {
                default: break;

                case TT_MISC_TUNNEL: {
                        assert(abs((int)GetSlopePixelZ(x, y) - u->z_pos) < 3);

                        /* Direction into the wormhole */
                        const DiagDirection dir = GetTunnelBridgeDirection(tile);

                        if (u->direction == DiagDirToDir(dir)) {
                                uint frame = DistanceFromTileEdge(ReverseDiagDir(dir), x & 0xF, y & 0xF);
                                if (u->IsFrontEngine() && frame == TUNNEL_SOUND_FRAME) {
                                        if (!PlayVehicleSound(u, VSE_TUNNEL) && RailVehInfo(u->engine_type)->engclass == 0) {
                                                SndPlayVehicleFx(SND_05_TRAIN_THROUGH_TUNNEL, u);
                                        }
                                }
                                if (frame == _tunnel_visibility_frame[dir]) {
                                        u->vehstatus |= VS_HIDDEN;
                                }
                        } else if (u->direction == ReverseDir(DiagDirToDir(dir))) {
                                uint frame = DistanceFromTileEdge(dir, x & 0xF, y & 0xF);
                                if (frame == TILE_SIZE - _tunnel_visibility_frame[dir]) {
                                        u->vehstatus &= ~VS_HIDDEN;
                                }
                        }

                        break;
                }

                case TT_MISC_DEPOT: {
                        if (!IsRailDepot(tile)) break;

                        /* depot direction */
                        DiagDirection dir = GetGroundDepotDirection(tile);

                        /* make sure a train is not entering the tile from behind */
                        assert(DistanceFromTileEdge(ReverseDiagDir(dir), x & 0xF, y & 0xF) != 0);

                        int fract_x = (int)(x & 0xF) - _vehicle_initial_x_fract[dir];
                        int fract_y = (int)(y & 0xF) - _vehicle_initial_y_fract[dir];

                        if (u->direction == DiagDirToDir(ReverseDiagDir(dir))) {
                                if (fract_x == 0 && fract_y == 0) {
                                        /* enter the depot */
                                        u->trackdir = TRACKDIR_DEPOT,
                                        u->vehstatus |= VS_HIDDEN; // hide it
                                        u->direction = ReverseDir(u->direction);
                                        if (u->Next() == NULL) TrainEnterDepot (u->First());
                                        u->tile = tile;

                                        InvalidateWindowData(WC_VEHICLE_DEPOT, u->tile);
                                }
                        } else if (u->direction == DiagDirToDir(dir)) {
                                static const int8 delta_x[4] = { -1,  0,  1,  0 };
                                static const int8 delta_y[4] = {  0,  1,  0, -1 };

                                /* Calculate the point where the following wagon should be activated. */
                                int length = u->CalcNextVehicleOffset() + 1;

                                if ((fract_x == length * delta_x[dir]) && (fract_y == length * delta_y[dir])) {
                                        /* leave the depot? */
                                        if ((u = u->Next()) != NULL) {
                                                u->vehstatus &= ~VS_HIDDEN;
                                                u->trackdir = DiagDirToDiagTrackdir(dir);
                                        }
                                }
                        }

                        break;
                }
        }
}

static StationID TrainEnter_Station(Train *v, TileIndex tile, int x, int y)
{
        StationID station_id = GetStationIndex(tile);
        if (!v->current_order.ShouldStopAtStation(v, station_id)) return INVALID_STATION;
        if (!IsRailStation(tile) || !v->IsFrontEngine()) return INVALID_STATION;

        int station_ahead;
        int station_length;
        int stop = GetTrainStopLocation(station_id, tile, Train::From(v), &station_ahead, &station_length);

        /* Stop whenever that amount of station ahead + the distance from the
         * begin of the platform to the stop location is longer than the length
         * of the platform. Station ahead 'includes' the current tile where the
         * vehicle is on, so we need to subtract that. */
        if (stop + station_ahead - (int)TILE_SIZE >= station_length) return INVALID_STATION;

        DiagDirection dir = DirToDiagDir(v->direction);

        x &= 0xF;
        y &= 0xF;

        if (DiagDirToAxis(dir) != AXIS_X) Swap(x, y);
        if (y == TILE_SIZE / 2) {
                if (dir != DIAGDIR_SE && dir != DIAGDIR_SW) x = TILE_SIZE - 1 - x;
                stop &= TILE_SIZE - 1;

                if (x == stop) {
                        return station_id; // enter station
                } else if (x < stop) {
                        v->vehstatus |= VS_TRAIN_SLOWING;
                        uint16 spd = max(0, (stop - x) * 20 - 15);
                        if (spd < v->cur_speed) v->cur_speed = spd;
                }
        }

        return INVALID_STATION;
}

/**
 * Call the tile callback function for a train entering a tile
 * @param v    Train entering the tile
 * @param tile Tile entered
 * @param x    X position
 * @param y    Y position
 * @return Station ID of an entered station, or INVALID_STATION otherwise
 */
static StationID TrainEnterTile(Train *v, TileIndex tile, int x, int y)
{
        switch (GetTileType(tile)) {
                default: NOT_REACHED();

                case TT_RAILWAY:
                        TrainEnter_Track(v, tile, x, y);
                        break;

                case TT_MISC:
                        TrainEnter_Misc(v, tile, x, y);
                        break;

                case TT_STATION:
                        return TrainEnter_Station(v, tile, x, y);
        }

        return INVALID_STATION;
}

/**
 * Choose the trackdir to follow when a train enters a new tile.
 * @param v The train that enters the tile
 * @param tile The tile entered
 * @param enterdir The direction the train is moving between tiles
 * @param tsdir The direction to use for GetTileRailwayStatus
 * @param check_90deg Check for 90-degree turns and disallow them
 * @param reverse Set to false to not execute the vehicle reversing. This does not change any other logic.
 * @return The trackdir to use, or INVALID_TRACKDIR if the train cannot go forward
 */
static Trackdir TrainControllerChooseTrackdir(Train *v, TileIndex tile, DiagDirection enterdir, DiagDirection tsdir, bool check_90deg, bool reverse)
{
        /* Get the status of the tracks in the new tile and mask
         * away the bits that aren't reachable. */
        TrackStatus ts = GetTileRailwayStatus(tile, tsdir);
        TrackdirBits reachable_trackdirs = DiagdirReachesTrackdirs(enterdir);

        TrackdirBits trackdirbits = TrackStatusToTrackdirBits(ts) & reachable_trackdirs;
        if (check_90deg) trackdirbits &= ~TrackdirCrossesTrackdirs(v->trackdir);

        TrackdirBits red_signals = TrackStatusToRedSignals(ts);

        /* Check if the new tile constrains tracks that are compatible
         * with the current train, if not, bail out. */
        if (trackdirbits == TRACKDIR_BIT_NONE || !CheckCompatibleRail(v, tile, TrackdirToTrack(FindFirstTrackdir(trackdirbits)))) {
                if (reverse) {
                        v->wait_counter = 0;
                        v->cur_speed = 0;
                        v->subspeed = 0;
                        ReverseTrainDirection(v);
                }

                return INVALID_TRACKDIR;
        }

        Trackdir chosen_trackdir;

        /* Don't use trackdirbits here as the setting to forbid 90 deg turns might have been switched between reservation and now. */
        TrackdirBits res_trackdirs = TrackBitsToTrackdirBits(GetReservedTrackbits(tile)) & reachable_trackdirs;
        /* Do we have a suitable reserved trackdir? */
        if (res_trackdirs != TRACKDIR_BIT_NONE) {
                chosen_trackdir = FindFirstTrackdir(res_trackdirs);
        } else {
                if (!ChooseTrainTrack (v, v->GetPos(),
                                PathMPos<RailPathPos> (tile, trackdirbits),
                                false, &chosen_trackdir)) {
                        MarkTrainAsStuck(v);
                }
                assert(chosen_trackdir != INVALID_TRACKDIR);
                assert(HasBit(trackdirbits, chosen_trackdir));
        }

        /* Make sure chosen trackdir is a valid trackdir */
        assert(IsValidTrackdir(chosen_trackdir));

        if (v->force_proceed != TFP_NONE) {
                /* For each signal we find decrease the counter by one.
                 * We start at two, so the first signal we pass decreases
                 * this to one, then if we reach the next signal it is
                 * decreased to zero and we won't pass that new signal. */
                bool at_signal;
                if (IsRailwayTile(tile)) {
                        Track track = TrackdirToTrack(chosen_trackdir);
                        /* However, we do not want to be stopped by PBS
                         * signals entered via the back. */
                        at_signal = HasSignalOnTrack(tile, track) &&
                                (GetSignalType(tile, track) != SIGTYPE_PBS ||
                                        HasSignalOnTrackdir(tile, chosen_trackdir));
                } else if (maptile_is_rail_tunnel(tile)) {
                        at_signal = maptile_has_tunnel_signals(tile);
                } else {
                        at_signal = false;
                }

                if (at_signal) {
                        v->force_proceed = (v->force_proceed == TFP_SIGNAL) ? TFP_STUCK : TFP_NONE;
                        SetWindowDirty(WC_VEHICLE_VIEW, v->index);
                }
        }

        /* Check if it's a red signal and if force proceed is clicked. */
        if (!HasBit(red_signals, chosen_trackdir) || v->force_proceed != TFP_NONE) {
                /* Proceed */
                TryReserveRailTrack(tile, TrackdirToTrack(chosen_trackdir), false);
                return chosen_trackdir;
        }

        /* In front of a red signal */
        assert(trackdirbits == TrackdirToTrackdirBits(chosen_trackdir));

        /* Don't handle stuck trains here. */
        if (HasBit(v->flags, VRF_TRAIN_STUCK)) return INVALID_TRACKDIR;

        bool is_track = IsRailwayTile (tile);

        SignalPair sp;
        bool is_along;
        if (is_track) {
                sp = *maptile_signalpair (tile, TrackdirToTrack (chosen_trackdir));
                is_along = trackdir_is_signal_along (chosen_trackdir);
        } else {
                assert (maptile_is_rail_tunnel (tile));
                assert (IsDiagonalTrackdir (chosen_trackdir));
                sp = *maptile_tunnel_signalpair (tile);
                /* For tunnels, along means inwards. */
                is_along = (chosen_trackdir == DiagDirToDiagTrackdir (GetTunnelBridgeDirection (tile)));
        }

        assert (signalpair_has_signals (&sp));

        /* Is the train stuck at the wrong side of a one-way signal? */
        bool blocked;

        if (!signalpair_has_signal (&sp, !is_along)) {
                /* No signal against; wait here for the signal to clear. */
                v->cur_speed = 0;
                v->subspeed = 0;
                v->progress = 255 - 100;
                if (!_settings_game.pf.reverse_at_signals || ++v->wait_counter < _settings_game.pf.wait_oneway_signal * 20) return INVALID_TRACKDIR;
                blocked = false;
        } else if (signalpair_has_signal (&sp, is_along)) {
                /* Signals both along and against. */
                v->cur_speed = 0;
                v->subspeed = 0;
                v->progress = 255 - 10;
                if ((!_settings_game.pf.reverse_at_signals || ++v->wait_counter < _settings_game.pf.wait_twoway_signal * 73)
                                && (is_track || !is_along)) {
                        DiagDirection exitdir = TrackdirToExitdir(chosen_trackdir);
                        TileIndex o_tile = TileAddByDiagDir(tile, exitdir);

                        exitdir = ReverseDiagDir(exitdir);

                        /* check if a train is waiting on the other side */
                        VehicleTileFinder iter (o_tile);
                        while (!iter.finished()) {
                                Vehicle *v = iter.next();
                                if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) continue;

                                Train *t = Train::From(v);
                                if (t->IsFrontEngine() && (t->trackdir < TRACKDIR_END) && (t->cur_speed <= 5) && TrackdirToExitdir(t->trackdir) == exitdir) {
                                        iter.set_found();
                                }
                        }
                        if (!iter.was_found()) return INVALID_TRACKDIR;
                }
                blocked = false;
        } else {
                /* Signal against, but not along; reverse immediately. */
                assert (IsOnewaySignal (signalpair_get_type (&sp)));
                blocked = true;
        }

        /* If we would reverse but are currently in a PBS block and
         * reversing of stuck trains is disabled, don't reverse.
         * This does not apply if the reason for reversing is a one-way
         * signal blocking us, because a train would then be stuck forever. */
        if (!blocked && !_settings_game.pf.reverse_at_signals) {
                assert(IsSignalBufferEmpty());
                AddPosToSignalBuffer(v->GetPos(), v->owner);
                if (UpdateSignalsInBuffer() == SIGSEG_PBS) {
                        v->wait_counter = 0;
                        return INVALID_TRACKDIR;
                }
        }

        if (reverse) {
                v->wait_counter = 0;
                v->cur_speed = 0;
                v->subspeed = 0;
                ReverseTrainDirection(v);
        }

        return INVALID_TRACKDIR;
}

/**
 * Move a vehicle chain one movement stop forwards.
 * @param v First vehicle to move.
 * @param nomove Stop moving this and all following vehicles.
 * @param reverse Set to false to not execute the vehicle reversing. This does not change any other logic.
 * @return True if the vehicle could be moved forward, false otherwise.
 */
bool TrainController(Train *v, Vehicle *nomove, bool reverse)
{
        Train *first = v->First();
        Train *prev;
        bool direction_changed = false; // has direction of any part changed?

        /* For every vehicle after and including the given vehicle */
        for (prev = v->Previous(); v != nomove; prev = v, v = v->Next()) {
                TileIndex old_tile; // old virtual tile
                bool old_in_wormhole; // whether old position was in wormhole
                enum {
                        WORMHOLE_NONE,
                        WORMHOLE_BRIDGE,
                        WORMHOLE_TUNNEL,
                } new_in_wormhole; // whether new position is in a wormhole, and of which kind
                DiagDirection enterdir = INVALID_DIAGDIR; // direction into the new tile, or INVALID_DIAGDIR if we stay on the old tile
                DiagDirection tsdir = INVALID_DIAGDIR; // direction to use for GetTileRailwayStatus, only when moving into a new tile

                FullPosTile gp = GetNewVehiclePos(v);
                if (v->trackdir == TRACKDIR_WORMHOLE) {
                        /* In a tunnel or on a bridge (middle part) */
                        old_tile = TileVirtXY(v->x_pos, v->y_pos);
                        old_in_wormhole = true;

                        if (gp.tile == v->tile) {
                                new_in_wormhole = WORMHOLE_NONE;
                                enterdir = ReverseDiagDir(GetTunnelBridgeDirection(gp.tile));
                                tsdir = INVALID_DIAGDIR;
                        } else if (!(v->vehstatus & VS_HIDDEN)) {
                                /* Still on the bridge. */
                                new_in_wormhole = WORMHOLE_BRIDGE;
                        } else {
                                /* Still in the tunnel. */
                                if (v->IsFrontEngine() && maptile_has_tunnel_signal (v->tile, false) && (FindTunnelPrevTrain(v) < TILE_SIZE)) {
                                        /* too close to train ahead, stop */
                                        return false;
                                }
                                new_in_wormhole = WORMHOLE_TUNNEL;
                        }
                } else if (v->trackdir == TRACKDIR_DEPOT) {
                        /* Inside depot */
                        assert(gp.tile == v->tile);
                        continue;
                } else if (gp.tile == v->tile) {
                        /* Not inside tunnel or depot, staying in the old tile */
                        old_tile = v->tile;
                        old_in_wormhole = false;
                        new_in_wormhole = WORMHOLE_NONE;
                } else {
                        /* Not inside tunnel or depot, about to enter a new tile */
                        old_tile = v->tile;
                        old_in_wormhole = false;

                        /* Determine what direction we're entering the new tile from */
                        enterdir = DiagdirBetweenTiles(v->tile, gp.tile);
                        assert(IsValidDiagDirection(enterdir));

                        if (IsTunnelTile(v->tile) && GetTunnelBridgeDirection(v->tile) == enterdir) {
                                TileIndex end_tile = GetOtherTunnelEnd(v->tile);
                                if (end_tile != gp.tile) {
                                        /* Entering a tunnel */
                                        new_in_wormhole = WORMHOLE_TUNNEL;
                                        gp.tile = end_tile;
                                } else {
                                        new_in_wormhole = WORMHOLE_NONE;
                                        tsdir = INVALID_DIAGDIR;
                                }
                        } else if (IsRailBridgeTile(v->tile) && GetTunnelBridgeDirection(v->tile) == enterdir) {
                                TileIndex end_tile = GetOtherBridgeEnd(v->tile);
                                if (end_tile != gp.tile) {
                                        /* Entering a bridge */
                                        new_in_wormhole = WORMHOLE_BRIDGE;
                                        gp.tile = end_tile;
                                        ClrBit(v->gv_flags, GVF_GOINGUP_BIT);
                                        ClrBit(v->gv_flags, GVF_GOINGDOWN_BIT);

                                        first->cur_speed = min(first->cur_speed, GetBridgeSpec(GetRailBridgeType(v->tile))->speed);
                                } else {
                                        new_in_wormhole = WORMHOLE_NONE;
                                        tsdir = INVALID_DIAGDIR;
                                }
                        } else {
                                new_in_wormhole = WORMHOLE_NONE;
                                tsdir = ReverseDiagDir(enterdir);
                        }
                }

                if (enterdir == INVALID_DIAGDIR) {
                        /* Staying on the same tile */

                        /* Reverse when we are at the end of the track already, do not move to the new position */
                        if ((new_in_wormhole == WORMHOLE_NONE) && v->IsFrontEngine() && !TrainCheckIfLineEnds(v, reverse)) return false;
                } else {
                        /* Entering a new tile */

                        Trackdir chosen_trackdir;
                        if (new_in_wormhole == WORMHOLE_BRIDGE) {
                                /* entering a bridge */
                                assert(!old_in_wormhole);
                                if (prev == NULL) {
                                        SetBridgeMiddleReservation (old_tile, true);
                                        SetBridgeMiddleReservation (gp.tile, true);
                                }
                        } else if (new_in_wormhole == WORMHOLE_TUNNEL) {
                                /* entering a tunnel */
                                assert(!old_in_wormhole);
                                if (prev == NULL) {
                                        SetTunnelMiddleReservation (old_tile, true);
                                        SetTunnelMiddleReservation (gp.tile, true);
                                }
                        } else if (prev == NULL) {
                                /* locomotive entering a new tile, so choose a track */
                                chosen_trackdir = TrainControllerChooseTrackdir(v, gp.tile, enterdir, tsdir, !old_in_wormhole && _settings_game.pf.forbid_90_deg, reverse);
                                if (chosen_trackdir == INVALID_TRACKDIR) return false;

                                bool mark_dirty = false;
                                if (IsRailwayTile (gp.tile)) {
                                        if (HasSignalOnTrackdir (gp.tile, chosen_trackdir) && IsPbsSignal (GetSignalType (gp.tile, TrackdirToTrack (chosen_trackdir)))) {
                                                SetSignalStateByTrackdir (gp.tile, chosen_trackdir, SIGNAL_STATE_RED);
                                                mark_dirty = true;
                                        }
                                } else if (old_in_wormhole) {
                                        assert (maptile_is_rail_tunnel (gp.tile));
                                        assert (TrackdirToExitdir (chosen_trackdir) != GetTunnelBridgeDirection (gp.tile));
                                        if (maptile_has_tunnel_signal (gp.tile, false) && IsPbsSignal (maptile_get_tunnel_signal_type (gp.tile))) {
                                                maptile_set_tunnel_signal_state (gp.tile, false, SIGNAL_STATE_RED);
                                                mark_dirty = true;
                                        }
                                }
                                if (mark_dirty) MarkTileDirtyByTile (gp.tile);
                        } else {
                                /* wagon entering a new tile, just follow the previous vehicle */
                                if (prev->tile == gp.tile) {
                                        /* Choose the same track as prev */
                                        assert(prev->trackdir != TRACKDIR_WORMHOLE);
                                        chosen_trackdir = prev->trackdir;
                                } else {
                                        /* Choose the track that leads to the tile where prev is.
                                         * This case is active if 'prev' is already on the second next tile, when 'v' just enters the next tile.
                                         * I.e. when the tile between them has only space for a single vehicle like
                                         *  1) horizontal/vertical track tiles and
                                         *  2) some orientations of tunnel entries, where the vehicle is already inside the wormhole at 8/16 from the tile edge.
                                         *     Is also the train just reversing, the wagon inside the tunnel is 'on' the tile of the opposite tunnel entry.
                                         */
                                        DiagDirection exitdir = DiagdirBetweenTiles(gp.tile, prev->tile);
                                        assert(IsValidDiagDirection(exitdir));
                                        chosen_trackdir = EnterdirExitdirToTrackdir(enterdir, exitdir);
                                        assert(!IsReversingRoadTrackdir(chosen_trackdir));
                                }

                                assert(CheckCompatibleRail(v, gp.tile, TrackdirToTrack(chosen_trackdir)));
                        }

                        if (v->Next() == NULL) {
                                /* Clear any track reservation when the last vehicle leaves the tile */
                                ClearPathReservation (v->GetPos());

                                RailPathPos rev = v->GetReversePos();
                                if (rev.has_signals()) {
                                        assert(IsSignalBufferEmpty());
                                        AddPosToSignalBuffer(rev, v->owner);
                                        /* Defer actual updating of signals until the train has moved */
                                }
                        }

                        Direction chosen_dir;
                        if (new_in_wormhole != WORMHOLE_NONE) {
                                /* Just entered the wormhole */
                                v->tile = gp.tile;
                                v->trackdir = TRACKDIR_WORMHOLE;
                                chosen_dir = DiagDirToDir(enterdir);
                        } else {
                                bool track_changed = !old_in_wormhole &&
                                        (GetRailType (v->tile, TrackdirToTrack(v->trackdir)) !=
                                                GetRailType (gp.tile, TrackdirToTrack(chosen_trackdir)));

                                v->tile = gp.tile;
                                v->trackdir = chosen_trackdir;

                                if (track_changed) {
                                        v->First()->ConsistChanged(CCF_TRACK);
                                }

                                /* Update XY to reflect the entrance to the new tile, and select the direction to use */
                                const InitialSubcoords *b = get_initial_subcoords (chosen_trackdir);
                                gp.adjust_subcoords (b);
                                chosen_dir = b->dir;
                        }

                        if (chosen_dir != v->direction) {
                                if (prev == NULL && _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
                                        const AccelerationSlowdownParams *asp = &_accel_slowdown[GetRailTypeInfo(v->railtype)->acceleration_type];
                                        DirDiff diff = DirDifference(v->direction, chosen_dir);
                                        v->cur_speed -= (diff == DIRDIFF_45RIGHT || diff == DIRDIFF_45LEFT ? asp->small_turn : asp->large_turn) * v->cur_speed >> 8;
                                }
                                direction_changed = true;
                                v->direction = chosen_dir;
                        }

                        /* update image of train, as well as delta XY */
                        v->UpdateDeltaXY(v->direction);
                }

                if (new_in_wormhole == WORMHOLE_NONE) {
                        /* Call the landscape function and tell it that the vehicle entered the tile */
                        StationID sid = TrainEnterTile(v, gp.tile, gp.xx, gp.yy);
                        if (sid != INVALID_STATION) {
                                /* The new position is the location where we want to stop */
                                TrainEnterStation(v, sid);
                        }
                }

                if (v->IsFrontEngine()) {
                        v->wait_counter = 0;

                        /* Always try to extend the reservation when entering a tile. */
                        bool check_next_tile;
                        if (new_in_wormhole == WORMHOLE_NONE) {
                                /* If we are approaching a crossing that is reserved, play the sound now. */
                                TileIndex crossing = TrainApproachingCrossingTile(v);
                                if (crossing != INVALID_TILE && HasCrossingReservation(crossing) && _settings_client.sound.ambient) SndPlayTileFx(SND_0E_LEVEL_CROSSING, crossing);

                                check_next_tile = enterdir != INVALID_DIAGDIR;
                        } else {
                                check_next_tile = (gp.tile != old_tile) &&
                                                DistanceAlongAxis (old_tile, v->tile) == 2;
                        }

                        if (check_next_tile) CheckNextTrainTile(v);
                }

                v->x_pos = gp.xx;
                v->y_pos = gp.yy;
                v->UpdatePosition();

                if (new_in_wormhole == WORMHOLE_BRIDGE) {
                        v->Vehicle::UpdateViewport (true);
                } else if (new_in_wormhole == WORMHOLE_NONE) {
                        /* update the Z position of the vehicle */
                        int old_z = v->z_pos;

                        if (enterdir != INVALID_DIAGDIR) {
                                v->ResetZPosition();

                                /* Only rail tiles can be sloped, and only
                                 * if they have a single trackbit and it is
                                 * along an axis. */
                                if (IsRailwayTile (v->tile)) {
                                        assert_compile (TRACK_BIT_X == 1);
                                        assert_compile (TRACK_BIT_Y == 2);
                                        if (GetTrackBits (v->tile) < 3) {
                                                v->UpdateInclination();
                                        }
                                }
                        } else {
                                if (HasBit(v->gv_flags, GVF_GOINGUP_BIT) || HasBit(v->gv_flags, GVF_GOINGDOWN_BIT)) {
                                        v->UpdateZPosition();
                                }
                                assert (v->z_pos == GetSlopePixelZ (v->x_pos, v->y_pos));
                        }

                        v->UpdateViewport (true, false);

                        if (prev == NULL) {
                                /* This is the first vehicle in the train */
                                AffectSpeedByZChange(v, old_z);
                        }
                }

                if (enterdir != INVALID_DIAGDIR) {
                        /* Update signals or crossing state if we changed tile */
                        /* Signals can only change when the first or the last vehicle moves. */
                        if (v->Next() == NULL) {
                                /* Update the signal segment added before, if any */
                                UpdateSignalsInBuffer();
                                if (!old_in_wormhole && IsLevelCrossingTile(old_tile)) UpdateLevelCrossing(old_tile);
                        }

                        if (v->IsFrontEngine()) {
                                RailPathPos pos = v->GetPos();
                                if (pos.has_signals()) {
                                        assert(IsSignalBufferEmpty());
                                        AddPosToSignalBuffer(pos, v->owner);

                                        if (UpdateSignalsInBuffer() == SIGSEG_PBS &&
                                                        pos.has_signal_along() &&
                                                        /* A PBS block with a non-PBS signal facing us? */
                                                        !IsPbsSignal(pos.get_signal_type())) {
                                                /* We are entering a block with PBS signals right now, but
                                                 * not through a PBS signal. This means we don't have a
                                                 * reservation right now. As a conventional signal will only
                                                 * ever be green if no other train is in the block, getting
                                                 * a path should always be possible. If the player built
                                                 * such a strange network that it is not possible, the train
                                                 * will be marked as stuck and the player has to deal with
                                                 * the problem. */
                                                TryReserveRailTrack(pos);
                                                /* Signals cannot be built on junctions, so
                                                 * a track on which there is a signal either
                                                 * is already reserved or can be reserved. */
                                                assert (HasReservedPos(pos));
                                                if (!TryPathReserve(v)) {
                                                        MarkTrainAsStuck(v);
                                                }
                                        }
                                }
                        }
                }

                if (old_in_wormhole && old_tile != gp.tile && v->Next() == NULL && maptile_is_rail_tunnel(v->tile) && maptile_has_tunnel_signal(v->tile, false)
                                && TileAddByDiagDir(old_tile, GetTunnelBridgeDirection(v->tile)) == GetOtherTunnelEnd(v->tile)) {
                        AddTunnelToSignalBuffer(v->tile, v->owner);
                        UpdateSignalsInBuffer();
                }

                /* Do not check on every tick to save some computing time. */
                if (v->IsFrontEngine() && v->tick_counter % _settings_game.pf.path_backoff_interval == 0
                                && (!old_in_wormhole || (DistanceAlongAxis (old_tile, v->tile) == 1))) {
                        CheckNextTrainTile(v);
                }
        }

        if (direction_changed) first->tcache.cached_max_curve_speed = first->GetCurveSpeedLimit();

        return true;
}


/**
 * Deletes/Clears the last wagon of a crashed train. It takes the engine of the
 * train, then goes to the last wagon and deletes that. Each call to this function
 * will remove the last wagon of a crashed train. If this wagon was on a crossing,
 * or inside a tunnel/bridge, recalculate the signals as they might need updating
 * @param v the Vehicle of which last wagon is to be removed
 */
static void DeleteLastWagon(Train *v)
{
        Train *first = v->First();

        /* Go to the last wagon and delete the link pointing there
         * *u is then the one-before-last wagon, and *v the last
         * one which will physically be removed */
        Train *u = v;
        for (; v->Next() != NULL; v = v->Next()) u = v;
        u->SetNext(NULL);

        if (first != v) {
                /* Recalculate cached train properties */
                first->ConsistChanged(CCF_ARRANGE);
                /* Update the depot window if the first vehicle is in depot -
                 * if v == first, then it is updated in PreDestructor() */
                if (first->trackdir == TRACKDIR_DEPOT) {
                        SetWindowDirty(WC_VEHICLE_DEPOT, first->tile);
                }
                v->last_station_visited = first->last_station_visited; // for PreDestructor
        }

        /* 'v' shouldn't be accessed after it has been deleted */
        Trackdir trackdir = v->trackdir;
        TileIndex tile = v->tile;
        Owner owner = v->owner;

        delete v;
        v = NULL; // make sure nobody will try to read 'v' anymore

        if (trackdir == TRACKDIR_DEPOT) return;

        if (trackdir == TRACKDIR_WORMHOLE) {
                TileIndex endtile = GetOtherTunnelBridgeEnd(tile);
                if (CheckTunnelBridgeMiddleFree (tile, endtile)) {
                        if (IsRailwayTile(tile)) {
                                SetBridgeMiddleReservation(tile, false);
                                SetBridgeMiddleReservation(endtile, false);
                        } else {
                                SetTunnelMiddleReservation(tile, false);
                                SetTunnelMiddleReservation(endtile, false);
                        }
                }

                assert(IsSignalBufferEmpty());
                if (IsRailwayTile(tile)) {
                        AddBridgeToSignalBuffer(tile, owner);
                } else {
                        AddTunnelToSignalBuffer(tile, owner);
                }
                UpdateSignalsInBuffer();
                return;
        }

        Track track = TrackdirToTrack(trackdir);
        if (HasReservedTrack(tile, track)) {
                UnreserveRailTrack(tile, track);

                /* If there are still crashed vehicles on the tile, give the track reservation to them */
                TrackBits remaining_trackbits = TRACK_BIT_NONE;
                VehicleTileIterator iter (tile);
                while (!iter.finished()) {
                        Vehicle *v = iter.next();
                        if (v->type == VEH_TRAIN && (v->vehstatus & VS_CRASHED) != 0) {
                                Trackdir trackdir = Train::From(v)->trackdir;
                                if (IsValidTrackdir (trackdir)) {
                                        remaining_trackbits |= TrackToTrackBits(TrackdirToTrack(trackdir));
                                }
                        }
                }

                /* It is important that these two are the first in the loop, as reservation cannot deal with every trackbit combination */
                assert_compile (TRACK_X == TRACK_BEGIN);
                assert_compile (TRACK_Y == TRACK_BEGIN + 1);
                Track t;
                FOR_EACH_SET_TRACK(t, remaining_trackbits) TryReserveRailTrack(tile, t);
        }

        /* check if the wagon was on a road/rail-crossing */
        if (IsLevelCrossingTile(tile)) UpdateLevelCrossing(tile);

        /* Update signals */
        assert(IsSignalBufferEmpty());
        if (IsRailDepotTile(tile)) {
                AddDepotToSignalBuffer(tile, owner);
        } else if (IsTunnelTile(tile)) {
                AddTunnelToSignalBuffer(tile, owner);
        } else {
                AddTrackToSignalBuffer(tile, track, owner);
        }
        UpdateSignalsInBuffer();
}

/**
 * Rotate all vehicles of a (crashed) train chain randomly to animate the crash.
 * @param v First crashed vehicle.
 */
static void ChangeTrainDirRandomly(Train *v)
{
        static const DirDiff delta[] = {
                DIRDIFF_45LEFT, DIRDIFF_SAME, DIRDIFF_SAME, DIRDIFF_45RIGHT
        };

        do {
                /* We don't need to twist around vehicles if they're not visible */
                if (!(v->vehstatus & VS_HIDDEN)) {
                        v->direction = ChangeDir(v->direction, delta[GB(Random(), 0, 2)]);
                        v->UpdateDeltaXY(v->direction);
                        v->GetImage(v->direction, EIT_ON_MAP, &v->sprite_seq);
                        if (v->trackdir != TRACKDIR_WORMHOLE) {
                                v->UpdatePosition();
                                v->UpdateViewport (true, false);
                        }
                }
        } while ((v = v->Next()) != NULL);
}

/**
 * Handle a crashed train.
 * @param v First train vehicle.
 * @return %Vehicle chain still exists.
 */
static bool HandleCrashedTrain(Train *v)
{
        int state = ++v->crash_anim_pos;

        if (state == 4 && !(v->vehstatus & VS_HIDDEN)) {
                CreateEffectVehicleRel(v, 4, 4, 8, EV_EXPLOSION_LARGE);
        }

        uint32 r;
        if (state <= 200 && Chance16R(1, 7, r)) {
                int index = (r * 10 >> 16);

                Vehicle *u = v;
                do {
                        if (--index < 0) {
                                r = Random();

                                CreateEffectVehicleRel(u,
                                        GB(r,  8, 3) + 2,
                                        GB(r, 16, 3) + 2,
                                        GB(r,  0, 3) + 5,
                                        EV_EXPLOSION_SMALL);
                                break;
                        }
                } while ((u = u->Next()) != NULL);
        }

        if (state <= 240 && !(v->tick_counter & 3)) ChangeTrainDirRandomly(v);

        if (state >= 4440 && !(v->tick_counter & 0x1F)) {
                bool ret = v->Next() != NULL;
                DeleteLastWagon(v);
                return ret;
        }

        return true;
}

/** Maximum speeds for train that is broken down or approaching line end */
static const uint16 _breakdown_speeds[16] = {
        225, 210, 195, 180, 165, 150, 135, 120, 105, 90, 75, 60, 45, 30, 15, 15
};


/**
 * Train is approaching line end, slow down and possibly reverse
 *
 * @param v front train engine
 * @param signal not line end, just a red signal
 * @param reverse Set to false to not execute the vehicle reversing. This does not change any other logic.
 * @return true iff we did NOT have to reverse
 */
static bool TrainApproachingLineEnd(Train *v, bool signal, bool reverse)
{
        /* Calc position within the current tile */
        uint x = v->x_pos & 0xF;
        uint y = v->y_pos & 0xF;

        /* for diagonal directions, 'x' will be 0..15 -
         * for other directions, it will be 1, 3, 5, ..., 15 */
        switch (v->direction) {
                case DIR_N : x = ~x + ~y + 25; break;
                case DIR_NW: x = y;            // FALL THROUGH
                case DIR_NE: x = ~x + 16;      break;
                case DIR_E : x = ~x + y + 9;   break;
                case DIR_SE: x = y;            break;
                case DIR_S : x = x + y - 7;    break;
                case DIR_W : x = ~y + x + 9;   break;
                default: break;
        }

        /* Do not reverse when approaching red signal. Make sure the vehicle's front
         * does not cross the tile boundary when we do reverse, but as the vehicle's
         * location is based on their center, use half a vehicle's length as offset.
         * Multiply the half-length by two for straight directions to compensate that
         * we only get odd x offsets there. */
        if (!signal && x + (v->gcache.cached_veh_length + 1) / 2 * (IsDiagonalDirection(v->direction) ? 1 : 2) >= TILE_SIZE) {
                /* we are too near the tile end, reverse now */
                v->cur_speed = 0;
                if (reverse) ReverseTrainDirection(v);
                return false;
        }

        /* slow down */
        v->vehstatus |= VS_TRAIN_SLOWING;
        uint16 break_speed = _breakdown_speeds[x & 0xF];
        if (break_speed < v->cur_speed) v->cur_speed = break_speed;

        return true;
}


/**
 * Determines whether a train is on the map and will stay on it after leaving the current tile
 * (as opposed to being in a wormhole or depot)
 * @param v train to test
 * @return true iff vehicle is NOT entering or inside a depot or tunnel/bridge
 */
static bool TrainStayOnMap(const Train *v)
{
        /* Exit if inside a tunnel/bridge or a depot */
        if (v->trackdir == TRACKDIR_WORMHOLE || v->trackdir == TRACKDIR_DEPOT) return false;

        TileIndex tile = v->tile;

        /* entering a tunnel/bridge? */
        if (IsRailBridgeTile(tile)) {
                if (TrackdirToExitdir(v->trackdir) == GetTunnelBridgeDirection(tile)) return false;
        }

        if (IsTunnelTile(tile)) {
                DiagDirection dir = GetTunnelBridgeDirection(tile);
                if (DiagDirToDir(dir) == v->direction) return false;
        }

        /* entering a depot? */
        if (IsRailDepotTile(tile)) {
                DiagDirection dir = ReverseDiagDir(GetGroundDepotDirection(tile));
                if (DiagDirToDir(dir) == v->direction) return false;
        }

        return true;
}


/**
 * Determines whether train is approaching a rail-road crossing
 *   (thus making it barred)
 * @param v front engine of train
 * @return TileIndex of crossing the train is approaching, else INVALID_TILE
 * @pre v in non-crashed front engine
 */
static TileIndex TrainApproachingCrossingTile(const Train *v)
{
        assert(v->IsFrontEngine());
        assert(!(v->vehstatus & VS_CRASHED));

        if (!TrainStayOnMap(v)) return INVALID_TILE;

        DiagDirection dir = TrackdirToExitdir(v->trackdir);
        TileIndex tile = v->tile + TileOffsByDiagDir(dir);

        /* not a crossing || wrong axis || unusable rail (wrong type or owner) */
        if (!IsLevelCrossingTile(tile) || DiagDirToAxis(dir) == GetCrossingRoadAxis(tile) ||
                        !CheckCompatibleRail(v, tile)) {
                return INVALID_TILE;
        }

        return tile;
}


/**
 * Checks for line end. Also, bars crossing at next tile if needed
 *
 * @param v vehicle we are checking
 * @param reverse Set to false to not execute the vehicle reversing. This does not change any other logic.
 * @return true iff we did NOT have to reverse
 */
static bool TrainCheckIfLineEnds(Train *v, bool reverse)
{
        /* First, handle broken down train */

        int t = v->breakdown_ctr;
        if (t > 1) {
                v->vehstatus |= VS_TRAIN_SLOWING;

                uint16 break_speed = _breakdown_speeds[GB(~t, 4, 4)];
                if (break_speed < v->cur_speed) v->cur_speed = break_speed;
        } else {
                v->vehstatus &= ~VS_TRAIN_SLOWING;
        }

        if (v->trackdir == TRACKDIR_WORMHOLE) {
                DiagDirection dir = GetTunnelBridgeDirection(v->tile);

                /* Only check when the train is on the last tile segment */
                if (TileVirtXY(v->x_pos, v->y_pos) != v->tile + TileOffsByDiagDir(dir)) return true;

                TrackStatus ts = GetTileRailwayStatus(v->tile, INVALID_DIAGDIR);
                TrackdirBits reachable_trackdirs = DiagdirReachesTrackdirs(ReverseDiagDir(dir));

                TrackdirBits trackdirbits = TrackStatusToTrackdirBits(ts) & reachable_trackdirs;
                TrackdirBits red_signals = TrackStatusToRedSignals(ts) & reachable_trackdirs;

                assert(trackdirbits != TRACKDIR_BIT_NONE);
                assert(CheckCompatibleRail(v, v->tile, TrackdirToTrack(FindFirstTrackdir(trackdirbits))));

                return (trackdirbits & red_signals) == 0 || TrainApproachingLineEnd(v, true, reverse);
        }

        if (!TrainStayOnMap(v)) return true;

        /* Determine the non-diagonal direction in which we will exit this tile */
        DiagDirection dir = TrackdirToExitdir(v->trackdir);
        /* Calculate next tile */
        TileIndex tile = v->tile + TileOffsByDiagDir(dir);

        /* Determine the track status on the next tile */
        TrackStatus ts = GetTileRailwayStatus(tile, ReverseDiagDir(dir));
        TrackdirBits reachable_trackdirs = DiagdirReachesTrackdirs(dir);

        TrackdirBits trackdirbits = TrackStatusToTrackdirBits(ts) & reachable_trackdirs;
        TrackdirBits red_signals = TrackStatusToRedSignals(ts) & reachable_trackdirs;

        /* We are sure the train is not entering a depot, it is detected above */

        /* mask unreachable track bits if we are forbidden to do 90deg turns */
        if (_settings_game.pf.forbid_90_deg) {
                trackdirbits &= ~TrackdirCrossesTrackdirs(v->trackdir);
        }

        /* no suitable trackbits at all || unusable rail (wrong type or owner) */
        if (trackdirbits == TRACKDIR_BIT_NONE || !CheckCompatibleRail(v, tile, TrackdirToTrack(FindFirstTrackdir(trackdirbits)))) {
                return TrainApproachingLineEnd(v, false, reverse);
        }

        /* approaching red signal */
        if ((trackdirbits & red_signals) != 0) return TrainApproachingLineEnd(v, true, reverse);

        /* approaching a rail/road crossing? then make it red */
        if (IsLevelCrossingTile(tile)) MaybeBarCrossingWithSound(tile);

        return true;
}


static bool TrainLocoHandler(Train *v, bool mode)
{
        /* train has crashed? */
        if (v->vehstatus & VS_CRASHED) {
                return mode ? true : HandleCrashedTrain(v); // 'this' can be deleted here
        }

        if (v->force_proceed != TFP_NONE) {
                ClrBit(v->flags, VRF_TRAIN_STUCK);
                SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
        }

        /* train is broken down? */
        if (v->HandleBreakdown()) return true;

        if (HasBit(v->flags, VRF_REVERSING) && v->cur_speed == 0) {
                ReverseTrainDirection(v);
        }

        /* exit if train is stopped */
        if ((v->vehstatus & VS_STOPPED) && v->cur_speed == 0) return true;

        bool valid_order = !v->current_order.IsType(OT_NOTHING) && v->current_order.GetType() != OT_CONDITIONAL;
        if (ProcessOrders(v) && CheckReverseTrain(v)) {
                v->wait_counter = 0;
                v->cur_speed = 0;
                v->subspeed = 0;
                ClrBit(v->flags, VRF_LEAVING_STATION);
                ReverseTrainDirection(v);
                return true;
        } else if (HasBit(v->flags, VRF_LEAVING_STATION)) {
                /* Try to reserve a path when leaving the station as we
                 * might not be marked as wanting a reservation, e.g.
                 * when an overlength train gets turned around in a station. */
                if (v->trackdir != TRACKDIR_DEPOT) {
                        assert(IsSignalBufferEmpty());
                        AddPosToSignalBuffer(v->GetPos(), v->owner);
                        if (UpdateSignalsInBuffer() == SIGSEG_PBS || _settings_game.pf.reserve_paths) {
                                TryPathReserve(v, true, true);
                        }
                }
                ClrBit(v->flags, VRF_LEAVING_STATION);
        }

        v->HandleLoading(mode);

        if (v->current_order.IsType(OT_LOADING)) return true;

        if (CheckTrainStayInDepot(v)) return true;

        if (!mode) v->ShowVisualEffect();

        /* We had no order but have an order now, do look ahead. */
        if (!valid_order && !v->current_order.IsType(OT_NOTHING)) {
                CheckNextTrainTile(v);
        }

        /* Handle stuck trains. */
        if (!mode && HasBit(v->flags, VRF_TRAIN_STUCK)) {
                ++v->wait_counter;

                /* Should we try reversing this tick if still stuck? */
                bool turn_around = v->wait_counter % (_settings_game.pf.wait_for_pbs_path * DAY_TICKS) == 0 && _settings_game.pf.reverse_at_signals;

                if (!turn_around && v->wait_counter % _settings_game.pf.path_backoff_interval != 0 && v->force_proceed == TFP_NONE) return true;
                if (!TryPathReserve(v)) {
                        /* Still stuck. */
                        if (turn_around) ReverseTrainDirection(v);

                        if (HasBit(v->flags, VRF_TRAIN_STUCK) && v->wait_counter > 2 * _settings_game.pf.wait_for_pbs_path * DAY_TICKS) {
                                /* Show message to player. */
                                if (_settings_client.gui.lost_vehicle_warn && v->owner == _local_company) {
                                        AddNewsItem<VehicleAdviceNewsItem> (STR_NEWS_TRAIN_IS_STUCK, v->index);
                                }
                                v->wait_counter = 0;
                        }
                        /* Exit if force proceed not pressed, else reset stuck flag anyway. */
                        if (v->force_proceed == TFP_NONE) return true;
                        ClrBit(v->flags, VRF_TRAIN_STUCK);
                        v->wait_counter = 0;
                        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                }
        }

        if (v->current_order.IsType(OT_LEAVESTATION)) {
                v->current_order.Clear();
                SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                return true;
        }

        int j = v->UpdateSpeed();

        /* we need to invalidate the widget if we are stopping from 'Stopping 0 km/h' to 'Stopped' */
        if (v->cur_speed == 0 && (v->vehstatus & VS_STOPPED)) {
                /* If we manually stopped, we're not force-proceeding anymore. */
                v->force_proceed = TFP_NONE;
                SetWindowDirty(WC_VEHICLE_VIEW, v->index);
        }

        int adv_spd = v->GetAdvanceDistance();
        if (j < adv_spd) {
                /* if the vehicle has speed 0, update the last_speed field. */
                if (v->cur_speed == 0) v->SetLastSpeed();
        } else {
                TrainCheckIfLineEnds(v);
                /* Loop until the train has finished moving. */
                for (;;) {
                        j -= adv_spd;
                        TrainController(v, NULL);
                        /* Don't continue to move if the train crashed. */
                        if (CheckTrainCollision(v)) break;
                        /* Determine distance to next map position */
                        adv_spd = v->GetAdvanceDistance();

                        /* No more moving this tick */
                        if (j < adv_spd || v->cur_speed == 0) break;

                        OrderType order_type = v->current_order.GetType();
                        /* Do not skip waypoints (incl. 'via' stations) when passing through at full speed. */
                        if ((order_type == OT_GOTO_WAYPOINT || order_type == OT_GOTO_STATION) &&
                                                (v->current_order.GetNonStopType() & ONSF_NO_STOP_AT_DESTINATION_STATION) &&
                                                IsStationTile(v->tile) &&
                                                v->current_order.GetDestination() == GetStationIndex(v->tile)) {
                                ProcessOrders(v);
                        }
                }
                v->SetLastSpeed();
        }

        for (Train *u = v; u != NULL; u = u->Next()) {
                if ((u->vehstatus & VS_HIDDEN) != 0) continue;

                u->UpdateViewport(false, false);
        }

        if (v->progress == 0) v->progress = j; // Save unused spd for next time, if TrainController didn't set progress

        return true;
}

/**
 * Get running cost for the train consist.
 * @return Yearly running costs.
 */
Money Train::GetRunningCost() const
{
        Money cost = 0;
        const Train *v = this;

        do {
                const Engine *e = v->GetEngine();
                if (e->u.rail.running_cost_class == INVALID_PRICE) continue;

                uint cost_factor = GetVehicleProperty(v, PROP_TRAIN_RUNNING_COST_FACTOR, e->u.rail.running_cost);
                if (cost_factor == 0) continue;

                /* Halve running cost for multiheaded parts */
                if (v->IsMultiheaded()) cost_factor /= 2;

                cost += GetPrice(e->u.rail.running_cost_class, cost_factor, e->GetGRF());
        } while ((v = v->GetNextVehicle()) != NULL);

        return cost;
}

/**
 * Update train vehicle data for a tick.
 * @return True if the vehicle still exists, false if it has ceased to exist (front of consists only).
 */
bool Train::Tick()
{
        this->tick_counter++;

        if (this->IsFrontEngine()) {
                if (!(this->vehstatus & VS_STOPPED) || this->cur_speed > 0) this->running_ticks++;

                this->current_order_time++;

                if (!TrainLocoHandler(this, false)) return false;

                return TrainLocoHandler(this, true);
        } else if (this->IsFreeWagon() && (this->vehstatus & VS_CRASHED)) {
                /* Delete flooded standalone wagon chain */
                if (++this->crash_anim_pos >= 4400) {
                        delete this;
                        return false;
                }
        }

        return true;
}

/**
 * Check whether a train needs service, and if so, find a depot or service it.
 * @return v %Train to check.
 */
static void CheckIfTrainNeedsService(Train *v)
{
        if (Company::Get(v->owner)->settings.vehicle.servint_trains == 0 || !v->NeedsAutomaticServicing()) return;
        if (v->IsChainInDepot()) {
                VehicleServiceInDepot(v);
                return;
        }

        FindDepotData tfdd;
        /* Only go to the depot if it is not too far out of our way. */
        if (!FindClosestTrainDepot(v, true, &tfdd)) {
                if (v->current_order.IsType(OT_GOTO_DEPOT)) {
                        /* If we were already heading for a depot but it has
                         * suddenly moved farther away, we continue our normal
                         * schedule? */
                        v->current_order.MakeDummy();
                        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                }
                return;
        }

        DepotID depot = GetDepotIndex(tfdd.tile);

        if (v->current_order.IsType(OT_GOTO_DEPOT) &&
                        v->current_order.GetDestination() != depot &&
                        !Chance16(3, 16)) {
                return;
        }

        SetBit(v->gv_flags, GVF_SUPPRESS_IMPLICIT_ORDERS);
        v->current_order.MakeGoToDepot(depot, ODTFB_SERVICE);
        v->dest_tile = tfdd.tile;
        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
}

/** Update day counters of the train vehicle. */
void Train::OnNewDay()
{
        AgeVehicle(this);

        if ((++this->day_counter & 7) == 0) DecreaseVehicleValue(this);

        if (this->IsFrontEngine()) {
                CheckVehicleBreakdown(this);

                CheckIfTrainNeedsService(this);

                CheckOrders(this);

                /* update destination */
                if (this->current_order.IsType(OT_GOTO_STATION)) {
                        TileIndex tile = Station::Get(this->current_order.GetDestination())->train_station.tile;
                        if (tile != INVALID_TILE) this->dest_tile = tile;
                }

                if (this->running_ticks != 0) {
                        /* running costs */
                        CommandCost cost(EXPENSES_TRAIN_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR  * DAY_TICKS));

                        this->profit_this_year -= cost.GetCost();
                        this->running_ticks = 0;

                        SubtractMoneyFromCompanyFract(this->owner, cost);

                        SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
                        SetWindowClassesDirty(WC_TRAINS_LIST);
                }
        }
}

/**
 * Get the trackdir of the train vehicle.
 * @return Current trackdir of the vehicle.
 */
Trackdir Train::GetTrackdir() const
{
        assert(!(this->vehstatus & VS_CRASHED));
        assert(this->trackdir != TRACKDIR_WORMHOLE);

        if (this->trackdir == TRACKDIR_DEPOT) {
                /* We'll assume the train is facing outwards */
                return DiagDirToDiagTrackdir(GetGroundDepotDirection(this->tile)); // Train in depot
        }

        return this->trackdir;
}

RailPathPos Train::GetPos() const
{
        if (this->vehstatus & VS_CRASHED) return RailPathPos();

        if (this->trackdir == TRACKDIR_WORMHOLE) {
                DiagDirection rev = GetTunnelBridgeDirection(this->tile);
                assert(ReverseDiagDir(rev) == DirToDiagDir(this->direction));
                return RailPathPos(TILE_ADD(this->tile, TileOffsByDiagDir(rev)), DiagDirToDiagTrackdir(ReverseDiagDir(rev)), this->tile);
        }

        return RailPathPos(this->tile, this->GetTrackdir());
}

RailPathPos Train::GetReversePos() const
{
        if (this->vehstatus & VS_CRASHED) return RailPathPos();

        if (this->trackdir == TRACKDIR_WORMHOLE) {
                TileIndex other_end = GetOtherTunnelBridgeEnd(this->tile);
                DiagDirection dir = GetTunnelBridgeDirection(other_end);
                assert(dir == DirToDiagDir(this->direction));
                return RailPathPos(TILE_ADD(other_end, TileOffsByDiagDir(dir)), DiagDirToDiagTrackdir(ReverseDiagDir(dir)), other_end);
        }

        return RailPathPos(this->tile, ReverseTrackdir(this->GetTrackdir()));
}