edit.lua

   1 local M = {}
   2
   3 -- XXX: in Lua 5.2 unpack() was moved into table
   4 local unpack = unpack or table.unpack
   5
   6 local swap = {["["] = "(", ["{"] = "[", ["("] = "{"}
   7
   8 local function startof(node) return node.start end
   9 local function finishof(node) return node.finish end
  10 local function is_comment(node) return node.is_comment end
  11
  12 local function normalize_spacing(start, delta, list)
  13         if delta > 0 then
  14                 table.insert(list, {start + delta, -delta})
  15         elseif delta < 0 then
  16                 table.insert(list, {start, -delta})
  17         end
  18         return delta
  19 end
  20
  21 local function leading_space(s, deltas, adj, parent, i, pstart, has_eol)
  22         local prev = parent[i - 1]
  23         if not s.indent and not (prev and (s.d == "|" or prev.d == "|")) and not has_eol then
  24                 local off = prev and prev.finish + 1 or pstart
  25                 adj = adj + normalize_spacing(off, s.start - off - (prev and 1 or 0), deltas)
  26         end
  27         return adj
  28 end
  29
  30 local function trailing_space(s, deltas, adj, parent, i, has_eol, keep_electric_space)
  31         local nxt = parent[i + 1]
  32         local is_last = not nxt
  33         if (is_last and not keep_electric_space) or nxt and nxt.indent then
  34                 local off = is_last and parent.finish - (has_eol and i < #parent and 1 or 0) or nxt.start - nxt.indent - 1
  35                 local finish = s.finish + (has_eol and i < #parent and 0 or 1)
  36                 normalize_spacing(finish, off - finish, deltas)
  37         end
  38         return adj
  39 end
  40
  41 local function indentation(s, deltas, adj, parent, i, pstart, base_indent, last_distinguished, first_argument,
  42         op_adj, indent_adj)
  43         if s.indent then
  44                 local delta = base_indent - s.indent
  45                 local firstarg_delta = base_indent + parent[1].finish + 2 - pstart - s.indent - op_adj - (indent_adj or 0)
  46                 if last_distinguished and i > 1 then
  47                         delta = delta + 1
  48                         if i - 1 <= last_distinguished then
  49                                 if parent[first_argument + 1].indent then
  50                                         delta = delta + 2
  51                                 else
  52                                         delta = firstarg_delta
  53                                 end
  54                         elseif last_distinguished < 0
  55                                 and i > first_argument + 1 and not parent[first_argument + 1].indent then
  56                                 delta = firstarg_delta
  57                         end
  58                 elseif i == 1 then
  59                         -- remove leading space
  60                         delta = -(s.start - pstart)
  61                 elseif                               -- align further arguments below the second one
  62                         parent.d == "("              -- [] and {} contain data, so no arguments
  63                         and not parent[1].is_string  -- a string can't have arguments
  64                         --and not parent[1].is_list  -- wrong, GNU Emacs compatible behaviour
  65                         then
  66                         if i > first_argument + 1 and not parent[first_argument + 1].indent then
  67                                 delta = firstarg_delta
  68                         end
  69                         if delta < 0 then delta = math.max(-s.indent, delta) end
  70                 end
  71                 if delta ~= 0 then
  72                         table.insert(deltas, {s.start, delta})
  73                 end
  74                 adj = adj - delta
  75         end
  76         return adj
  77 end
  78
  79 local function is_lone_prefix(node)
  80         return node and node.p and (#node.p == node.finish - node.start + 1)
  81 end
  82
  83 function M.new(parser, walker, fmt, write, delete, eol_at)
  84
  85         local function refmt_list(parent, base_indent, padj, deltas, keep_electric_space)
  86                 local adj = 0
  87                 local op_adj = 0
  88                 local indent_adj = 0
  89                 local pstart = parent.start + (parent.p and #parent.p or 0) + #parent.d
  90                 if parent.is_empty then
  91                         normalize_spacing(pstart, parent.finish - pstart, deltas)
  92                         return deltas
  93                 end
  94                 local last_distinguished = fmt:last_distinguished(parent)
  95                 local first_argument = 1
  96                 if #parent > 2 and parent[1].is_list and #parent[1] > 1 then
  97                         local op = parent[1]
  98                         local nearest_indented = op[#op].indent and op[#op] or walker.indented_before(op[#op])
  99                         indent_adj = nearest_indented.start - pstart - nearest_indented.indent + 1
 100                 end
 101                 for i, s in ipairs(parent) do
 102                         adj = s.indent and 0 or adj
 103                         if last_distinguished then
 104                                 -- do not let early comments influence the indentation of real expressions:
 105                                 if i <= last_distinguished and s.is_comment then
 106                                         last_distinguished = last_distinguished + 1
 107                                 end
 108                                 -- s is the name of a named let. account for it:
 109                                 if i == last_distinguished + 1 and not s.is_list and parent[1].text == "let" then
 110                                         last_distinguished = last_distinguished + 1
 111                                 end
 112                                 -- do not let early comments influence the indentation of real expressions:
 113                         elseif i <= first_argument + 1 and s.is_comment then
 114                                 first_argument = first_argument + 1
 115                         end
 116                         local has_eol = s.is_line_comment
 117                         adj = leading_space(s, deltas, adj, parent, i, pstart, has_eol)
 118                         adj = trailing_space(s, deltas, adj, parent, i, has_eol, keep_electric_space)
 119                         adj = indentation(s, deltas, adj, parent, i, pstart, base_indent, last_distinguished, first_argument,
 120                                 op_adj, indent_adj)
 121                         if i == 1 then
 122                                 op_adj = adj
 123                         end
 124                         if s.is_list then
 125                                 local nearest_indented = s.indent and s or walker.indented_before(s)
 126                                 local parent_column = nearest_indented and
 127                                         nearest_indented.indent + (s.start + (s.p and #s.p or 0) + #s.d) - nearest_indented.start
 128                                         or base_indent + (s.start + (s.p and #s.p or 0) + #s.d) - pstart
 129                                 refmt_list(s, parent_column - adj, padj + adj, deltas, keep_electric_space)
 130                         end
 131                 end
 132                 return deltas
 133         end
 134
 135         local function path_from(range)
 136                 local _, parent_at, m = walker.sexp_at(range, true)
 137                 local path
 138                 if parent_at[m] then
 139                         path = walker.sexp_path(parent_at[m])
 140                         local base = parent_at[m]
 141                         if range.finish == base.finish + 1 then
 142                                 path.after_finish = 0  -- lists can end up with a different length
 143                         else
 144                                 path.after_start = range.start - base.start
 145                         end
 146                 else
 147                         local s = parent_at[#parent_at]
 148                         if not s or range.start >= s.finish + 1 + (s.is_line_comment and 1 or 0) then
 149                                 path = walker.sexp_path(parent_at)
 150                                 path.at_pfinish = true
 151                         else
 152                                 local prev, n = parent_at.before(range.start, finishof)
 153                                 if prev then
 154                                         path = walker.sexp_path(prev)
 155                                         local nxt = parent_at[n + 1]
 156                                         path.after_finish = nxt and not nxt.indent and 1 or range.finish - prev.finish - 1
 157                                 else
 158                                         path = walker.sexp_path(parent_at[1])
 159                                         path.after_start = 0
 160                                 end
 161                         end
 162                 end
 163                 return path
 164         end
 165
 166         local function pos_from(path, range)
 167                 local sexp, parentng, n = walker.goto_path(path)
 168                 if sexp then
 169                         if path.after_finish then
 170                                 local nxt = n and parentng[n + 1]
 171                                 local max = nxt and nxt.start - sexp.finish - 1
 172                                 return sexp.finish + 1 - (range.finish - range.start) +
 173                                         (max and math.min(path.after_finish, max) or path.after_finish)
 174                         elseif path.at_pfinish then
 175                                 return sexp.finish
 176                         else
 177                                 return sexp.start + path.after_start
 178                         end
 179                 end
 180         end
 181
 182         local function refmt_at(scope, range, keep_electric_space)
 183                 if not range or not scope or scope.is_root or (scope.finish - scope.start < 2) then return range.start end
 184                 local parent = walker.sexp_at(scope, true)
 185                 if not (parent and parent.is_list) then return range.start end
 186                 local path = path_from(range)
 187                 local indented_parent = parent.indent and parent or parent.is_list and walker.indented_before(parent)
 188                 local parent_column = indented_parent and (indented_parent.indent + parent.start - indented_parent.start +
 189                         (parent.p and #parent.p or 0) + #parent.d) or
 190                         0
 191                 local deltas = refmt_list(parent, parent_column, 0, {}, keep_electric_space)
 192                 table.sort(deltas, function(d1, d2) return d1[1] > d2[1] end)
 193                 for _, pair in ipairs(deltas) do
 194                         local offset, delta = unpack(pair)
 195                         if delta > 0 then
 196                                 write(offset, string.rep(" ", delta))
 197                         elseif delta < 0 then
 198                                 delete(offset + delta, -delta)
 199                         end
 200                 end
 201                 parser.tree.rewind(parent.start or 0)
 202                 return path and pos_from(path, range) or range.start
 203         end
 204
 205         local function splice(pos, sexps, skip, backwards, action)
 206                 local spliced
 207                 local sexp = walker.sexp_at(skip, true)
 208                 local start = sexp.start + (sexp.p and #sexp.p or 0)
 209                 -- XXX: don't splice empty line comments _yet_. See _join_or_splice
 210                 local tosplice = action.splice or action.wrap or not sexp.is_line_comment and sexp.is_empty
 211                 local opening = (sexp.p or "")..sexp.d
 212                 local closing = parser.opposite[sexp.d]
 213                 local real_start = tosplice and sexp.start or start + #sexp.d
 214                 local splice_closing = not sexp.is_line_comment or sexp.is_empty
 215                 local real_finish = sexp.finish + 1 - (tosplice and splice_closing and 0 or #closing)
 216                 local first = backwards and
 217                         {start = real_start, finish = math.max(pos, start + #sexp.d)} or
 218                         {start = real_start, finish = sexp.is_empty and pos or start + #sexp.d}
 219                 local second = backwards and
 220                         {start = sexp.is_empty and pos or sexp.finish + 1 - #closing, finish = real_finish} or
 221                         {start = math.min(pos, sexp.finish + 1 - #closing), finish = real_finish}
 222                 action.func(second)
 223                 action.func(first)
 224                 spliced = tosplice
 225                 if action.kill then
 226                         local ndeleted = first.finish - first.start + second.finish - second.start
 227                         if ndeleted > 0 then
 228                                 sexps.rewind(sexp.start)
 229                         end
 230                 end
 231                 return first.finish - first.start, spliced, opening, closing
 232         end
 233
 234         -- If you try to delete some part of indentation, this function joins the current line with
 235         -- the previous one, unless the latter is a line comment.
 236         -- it does this by
 237         -- a) extending or shrinking the range that is to be deleted
 238         -- b) returning a truthy value to trick pick_out to glide the cursor, but refmt to restore the deleted spaces
 239         -- c) both a) and b)
 240         local function delete_indentation(range, pos)
 241                 local node, parent = walker.sexp_at(range)
 242                 if node or not parent.is_list then return end
 243                 local prev = parent.before(pos, finishof)
 244                 local nxt = parent.after(pos, startof)
 245                 if prev and prev.finish >= range.start or nxt and nxt.start < range.finish then return end
 246                 local backwards = pos == range.finish
 247                 local adj = 0
 248                 local eol = eol_at(pos)
 249                 local on_empty_line = not nxt or eol and nxt.start > eol
 250                 local empty_line_after_comment = prev and prev.is_line_comment
 251                         and on_empty_line
 252                 if nxt and nxt.indent then
 253                         if backwards and prev then
 254                                 range.start = prev.finish + (empty_line_after_comment and 0 or 1)
 255                                 if not prev.d then
 256                                         range.finish = range.start + 1
 257                                         adj = (on_empty_line and 0 or 1)
 258                                 end
 259                         end
 260                         return adj
 261                 end
 262                 if not nxt and prev then
 263                         range.start = prev.finish + 1
 264                         range.finish = parent.finish
 265                 elseif nxt and nxt.start == range.finish and (not prev or prev.finish + 1 == range.start) then
 266                         if prev and prev.d or nxt and nxt.d and not is_lone_prefix(prev) then
 267                                 -- don't delete spaces near delimiters, just slide the cursor:
 268                                 if backwards then
 269                                         range.finish = range.start
 270                                 else
 271                                         range.start = range.finish
 272                                 end
 273                         end
 274                         return adj
 275                 end
 276         end
 277
 278         local function big_enough_parent(pos1, pos2)
 279                 -- since the pos1-pos2 range can cross list boundaries, find which list contains both pos1 and pos2
 280                 local _, p1, p2
 281                 _, p1 = walker.sexp_at({start = pos1, finish = pos1}, true)
 282                 if p1.is_root or not (p1.start < pos1 and p1.finish > pos2) then
 283                         _, p2 = walker.sexp_at({start = pos2, finish = pos2}, true)
 284                 end
 285                 return p2 and not p2.is_root and p2 or p1
 286         end
 287
 288         local function extend_overlap(range)
 289                 local rnode = walker.sexp_at({start = range.finish, finish = range.finish})
 290                 if rnode and rnode.p and rnode.p:find";"
 291                         and range.finish > rnode.start and range.finish < rnode.start + #rnode.p then
 292                         return {start = range.start, finish = rnode.start + #rnode.p}
 293                 end
 294                 return range
 295         end
 296
 297         local function pick_out(range, pos, action)
 298                 local ndeleted = 0
 299                 if range.start == range.finish then return ndeleted end
 300                 local sexps = parser.tree
 301                 local skips = sexps.unbalanced_delimiters(range)
 302                 -- handle splice and kill-splice of forms and strings:
 303                 if #skips == 1 then
 304                         local sexp = walker.sexp_at(skips[1], true)
 305                         local backward_splice = skips[1].opening and pos >= sexp.start + (sexp.p and #sexp.p or 0) + #sexp.d
 306                                 and range.start >= sexp.start
 307                         local forward_splice = skips[1].closing and pos <= sexp.finish + 1 - #parser.opposite[sexp.d]
 308                                 and range.finish <= sexp.finish + 1
 309                         if backward_splice or forward_splice then
 310                                 return splice(backward_splice and range.finish or range.start, sexps, sexp, backward_splice, action)
 311                         end
 312                 end
 313                 local node, parent = walker.sexp_at({start = range.finish, finish = range.finish})
 314                 -- if the range ends with a line comment, don't delete its closing newline:
 315                 local drop_eol = action.kill and node and
 316                         node.finish + 1 == range.finish and node.is_line_comment
 317                 local par = big_enough_parent(range.start, range.finish)
 318                 local operator_changed = par[1] and par[1].finish >= range.start
 319                 local refmt = #skips == 0 and delete_indentation(range, pos) or operator_changed and 0
 320                 table.sort(skips, function(a, b) return a.start < b.start end)
 321                 table.insert(skips, {start = range.finish - (drop_eol and 1 or 0)})
 322                 table.insert(skips, 1, {finish = range.start})
 323                 ndeleted = ndeleted + (drop_eol and 1 or 0)
 324                 for i = #skips - 1, 1, -1 do
 325                         local region = {start = skips[i].finish, finish = skips[i + 1].start}
 326                         if skips[i].closing and skips[i + 1].opening then
 327                                 -- leave out some of the space between adjacent lists
 328                                 local _, rparent = walker.sexp_at(region)
 329                                 local nxt = rparent.after(region.start, startof)
 330                                 region.start = nxt and nxt.start or region.start
 331                         end
 332                         if action then
 333                                 action.func(region)
 334                                 ndeleted = ndeleted + (region.finish - region.start)
 335                         end
 336                 end
 337                 -- if parent[#parent + 1] is nil, we are at EOF
 338                 if ndeleted > 0 and (not parent.is_root or parent.is_parsed(range.start) or parent[#parent + 1]) then
 339                         sexps.rewind(range.start)
 340                 end
 341                 return ndeleted - (refmt or 0), nil, nil, nil, refmt
 342         end
 343
 344         local function raise_sexp(range, pos)
 345                 local sexp, parent = walker.sexp_at(range, true)
 346                 if sexp and parent and parent.is_list then
 347                         delete(sexp.finish + 1, parent.finish - sexp.finish)
 348                         delete(parent.start, sexp.start - parent.start)
 349                         parser.tree.rewind(parent.start)
 350                         range.start = parent.start + pos - sexp.start
 351                         range.finish = range.start
 352                         local _, nodes = walker.sexp_path(range)
 353                         local grandparent = nodes[#nodes - 2]
 354                         return grandparent and refmt_at(grandparent, range) or range.start
 355                 end
 356         end
 357
 358         local function slurp_sexp(range, forward)
 359                 local _, parent = walker.sexp_at(range, true)
 360                 local seeker = forward and walker.finish_after or walker.start_before
 361                 if not parent or not parent.is_list then return range.start end
 362                 local r = {start = parent.start, finish = parent.finish + 1}
 363                 local newpos = seeker(r, is_comment)
 364                 if not newpos then return range.start end
 365                 local opening = (parent.p or "")..parent.d
 366                 local closing = parser.opposite[parent.d]
 367                 local delimiter = forward and closing or opening
 368                 if forward then
 369                         write(newpos, delimiter)
 370                 end
 371                 delete(forward and parent.finish or parent.start, #delimiter)
 372                 if not forward then
 373                         write(newpos, delimiter)
 374                 end
 375                 parser.tree.rewind(math.min(parent.start, newpos))
 376                 return refmt_at(big_enough_parent(newpos, range.start), range)
 377         end
 378
 379         local function barf_sexp(range, forward)
 380                 local _, parent = walker.sexp_at(range, true)
 381                 local seeker = forward and walker.finish_before or walker.start_after
 382                 -- TODO: barfing out of strings requires calling the parser on them
 383                 if not parent or not parent.is_list or parent.is_empty then return range.start end
 384                 local opening = (parent.p or "")..parent.d
 385                 local pstart = parent.start + #opening
 386                 local r = {start = forward and parent.finish - 1 or pstart, finish = forward and parent.finish or pstart + 1}
 387                 local newpos = seeker(r, is_comment) or forward and pstart or parent.finish
 388                 local closing = parser.opposite[parent.d]
 389                 local delimiter = forward and closing or opening
 390                 if not forward then
 391                         write(newpos, delimiter)
 392                 end
 393                 delete(forward and parent.finish or parent.start, #delimiter)
 394                 if forward then
 395                         write(newpos, delimiter)
 396                 end
 397                 parser.tree.rewind(math.min(parent.start, newpos))
 398                 local drag = forward and (newpos < range.finish) or not forward and (newpos > range.start)
 399                 local keep_inside = forward and #parent > 1 and range.finish > range.start and 1 or 0
 400                 newpos = drag and newpos - keep_inside or range.start
 401                 local rangeng = {start = newpos, finish = newpos}
 402                 return refmt_at(big_enough_parent(newpos, parent.finish + 1), rangeng)
 403         end
 404
 405         local function splice_sexp(range, _, no_refmt)
 406                 local _, parent = walker.sexp_at(range)
 407                 if not parent or not parent.d then return end
 408                 local opening = (parent.p or "")..parent.d
 409                 local closing = parser.opposite[parent.d]
 410                 local finish = parent.finish + 1 - #closing
 411                 if not parent.is_line_comment then
 412                         delete(finish, #closing)
 413                 end
 414                 -- TODO: (un)escape special characters, if necessary
 415                 delete(parent.start, parent.is_empty and (finish - parent.start) or #opening)
 416                 parser.tree.rewind(parent.start)
 417                 range.start = range.start - #opening
 418                 range.finish = range.start
 419                 local _, parentng = walker.sexp_at(range, true)
 420                 return not no_refmt and refmt_at(parentng, range) or range.start
 421         end
 422
 423         local function rewrap(parent, kind)
 424                 local pstart = parent.start + #((parent.p or "")..parent.d) - 1
 425                 delete(parent.finish, 1)
 426                 write(parent.finish, parser.opposite[kind])
 427                 delete(pstart, #parent.d)
 428                 write(pstart, kind)
 429                 parser.tree.rewind(parent.start)
 430         end
 431
 432         local function cycle_wrap(range, pos)
 433                 local _, parent = walker.sexp_at(range)
 434                 if not parent or not parent.is_list then return end
 435                 local next_kind = {["("] = "[", ["["] = "{", ["{"] = "("}
 436                 rewrap(parent, next_kind[parent.d])
 437                 return pos
 438         end
 439
 440         local function split_sexp(range)
 441                 local _, parent = walker.sexp_at(range)
 442                 if not (parent and parent.d) then return end
 443                 local new_finish, new_start
 444                 if parent.is_list then
 445                         local prev = parent.before(range.start, finishof, is_comment)
 446                         new_finish = prev and prev.finish + 1
 447                         -- XXX: do not skip comments here, so they end up in the second list
 448                         -- and are not separated from their target expression:
 449                         local nxt = new_finish and parent.after(new_finish, startof)
 450                         new_start = nxt and nxt.start
 451                 else
 452                         new_start = range.start
 453                         new_finish = range.start
 454                 end
 455                 if not (new_start and new_finish) then return end
 456                 local opening = (parent.p or "")..parent.d
 457                 local closing = parser.opposite[parent.d]
 458                 write(new_start, opening)
 459                 local sep = parent.is_line_comment and ""  -- line comments already have a separator
 460                         or new_finish == new_start and " "  -- only add a separator if there was none before
 461                         or ""
 462                 write(new_finish, closing..sep)
 463                 parser.tree.rewind(parent.start)
 464                 range.start = new_start + (parent.is_list and 0 or #opening + #closing)
 465                 range.finish = range.start
 466                 local _, nodes = walker.sexp_path(range)
 467                 local parentng, grandparent = nodes[#nodes - 1], nodes[#nodes - 2]
 468                 local scope = parentng and not parentng.is_root and parentng or grandparent
 469                 return refmt_at(scope, range)
 470         end
 471
 472         local function join_sexps(range)
 473                 local node, parent = walker.sexp_at(range, true)
 474                 local first = node and node.finish + 1 == range.start and node or parent.before(range.start, finishof)
 475                 local second = first ~= node and node or parent.after(range.start, startof)
 476                 if not (first and second and first.d and
 477                         -- don't join line comments to margin comments:
 478                         (not first.is_line_comment or first.indent and second.indent) and
 479                         (first.d == second.d or
 480                                 -- join line comments even when their delimiters differ slightly
 481                                 -- (different number of semicolons, existence/lack of a space after them)
 482                                 parser.opposite[first.d] == parser.opposite[second.d])) then
 483                         return
 484                 end
 485                 local opening = (second.p or "")..second.d
 486                 local closing = parser.opposite[first.d]
 487                 local pos
 488                 if not first.is_list then
 489                         pos = first.finish + 1 - #closing
 490                         delete(pos, second.start + #opening - pos)
 491                 else
 492                         delete(second.start, #opening)
 493                         delete(first.finish, #closing)
 494                         pos = second.start - #closing
 495                 end
 496                 parser.tree.rewind(first.start)
 497                 range.start = pos
 498                 range.finish = range.start
 499                 local _, nodes = walker.sexp_path(range)
 500                 local parentng, grandparent = nodes[#nodes - 1], nodes[#nodes - 2]
 501                 local scope = parentng and not parentng.is_root and parentng or grandparent
 502                 return refmt_at(scope, range)
 503         end
 504
 505         local function delete_splicing(range, pos, splicing, delete_and_yank)
 506                 local action = {kill = true, wrap = splicing, splice = splicing, func = delete_and_yank}
 507                 local sexp, parent, n = walker.sexp_at(range, true)
 508                 range = extend_overlap(range)
 509                 local ndeleted, spliced = pick_out(range, pos, action)
 510                 local closing = spliced and parser.opposite[sexp.d]
 511                 local inner_list_len = spliced and sexp.finish - sexp.start + 1 - #sexp.d - #closing
 512                 local range_len = range.finish - range.start
 513                 local backwards = pos == range.finish
 514                 local whole_object = sexp and
 515                         (sexp.start == range.start and sexp.finish + 1 == range.finish
 516                         or spliced and (inner_list_len <= (backwards and range_len + ndeleted or range_len)))
 517                 local in_head_atom = sexp and not sexp.d and n == 1 and #parent > 1
 518                 local in_whitespace = not sexp
 519                 if whole_object or in_whitespace or in_head_atom then
 520                         local cur = whole_object and sexp.start or range.start
 521                         -- if parent[#parent + 1] is nil, we are at EOF
 522                         if not parent.is_root or parent.is_parsed(cur) or parent[#parent + 1] then
 523                                 parser.tree.rewind(cur)
 524                         end
 525                         local r = {start = cur, finish = cur}
 526                         local _, parentng = walker.sexp_at(r, true)
 527                         return refmt_at(parentng, r)
 528                 end
 529                 return spliced and (backwards and sexp.start or range.start - ndeleted)
 530                         or not backwards and ndeleted <= 0 and range.finish - ndeleted
 531                         or backwards and ndeleted <= 0 and range.start + ndeleted
 532                         or range.start
 533         end
 534
 535         local function transpose(range, first, second)
 536                 if not (first and second) then return end
 537                 local copy1 = first.text
 538                 local copy2 = second.text
 539                 delete(second.start, second.finish + 1 - second.start)
 540                 write(second.start, copy1)
 541                 delete(first.start, first.finish + 1 - first.start)
 542                 write(first.start, copy2)
 543                 parser.tree.rewind(first.start)
 544                 range.start = second.finish + 1
 545                 range.finish = range.start
 546                 return refmt_at(big_enough_parent(first.start, second.finish), range)
 547         end
 548
 549         local function transpose_sexps(range)
 550                 local node, parent = walker.sexp_at(range, true)
 551                 local first = node and node.finish + 1 == range.start and node or parent.before(range.start, finishof)
 552                 local second = first ~= node and node or parent.after(range.start, startof)
 553                 return transpose(range, first, second)
 554         end
 555
 556         local function transpose_words(range)
 557                 local _, first = walker.start_float_before(range)
 558                 local _, second = walker.finish_float_after(range)
 559                 if first and second and first.start == second.start then
 560                         _, first = walker.start_float_before(first)
 561                 end
 562                 return transpose(range, first, second)
 563         end
 564
 565         local function transpose_chars(range)
 566                 local node, parent, i = walker.sexp_at(range)
 567                 local nxt = i and parent[i + 1]
 568                 local pstart = not parent.is_root and parent.start + (parent.p and #parent.p or 0) + #parent.d
 569                 local pfinish = not parent.is_root and parent.finish
 570                 local npref = node and node.p and node.start + #node.p
 571                 -- only allow transposing while inside atoms/words and prefixes
 572                 if node and ((npref and (range.start <= npref and range.start > node.start) or
 573                         node.d and range.start > node.finish + 1) or not node.d and (not pstart or range.start > pstart)) then
 574                         local start = range.start -
 575                                 ((range.start == pfinish or range.start == npref or
 576                                 range.start == node.finish + 1 and (parent.is_list or parent.is_root) and (not nxt or nxt.indent)) and 1 or 0)
 577                         local str_start = start - node.start + 1
 578                         local char = node.text:sub(str_start, str_start)
 579                         delete(start, 1)
 580                         write(start - 1, #char > 0 and char or " ")
 581                         parser.tree.rewind(start)
 582                         local in_head_atom = i == 1 and #parent > 1
 583                         return parent.is_list and in_head_atom and refmt_at(parent, {start = start + 1, finish = start + 1}) or start + 1
 584                 end
 585         end
 586
 587         local function _join_or_splice(parent, n, range, pos)
 588                 local sexp = parent[n]
 589                 local nxt = parent[n + 1]
 590                 local is_last = not nxt or not nxt.is_line_comment
 591                 local newpos = not (is_last and sexp.is_empty) and join_sexps(range)
 592                 if not newpos and sexp.is_empty then
 593                         newpos = splice_sexp({start = pos, finish = pos}, nil, true)
 594                 end
 595                 return newpos or pos
 596         end
 597
 598         local function delete_nonsplicing(range, pos, delete_maybe_yank)
 599                 local action = {kill = true, wrap = false, splice = false, func = delete_maybe_yank}
 600                 range = extend_overlap(range)
 601                 local ndeleted, spliced, opening, _, refmt = pick_out(range, pos, action)
 602                 local backwards = pos == range.finish
 603                 if opening then
 604                         if spliced then
 605                                 return pos - ndeleted
 606                         else
 607                                 if ndeleted == 0 then
 608                                         local closing = parser.opposite[opening] -- XXX: why don't I use the pick_out return value?
 609                                         if closing == "\n" then
 610                                                 local sexp, parent, n = walker.sexp_at(range)
 611                                                 if pos == sexp.start + #sexp.d and backwards then
 612                                                         return _join_or_splice(parent, n, range, pos)
 613                                                 elseif pos == sexp.finish then
 614                                                         local r = {start = pos + #closing, finish = pos + #closing}
 615                                                         return _join_or_splice(parent, n, r, pos)
 616                                                 end
 617                                         end
 618                                 end
 619                                 return backwards and (range.finish - ndeleted) or range.start
 620                         end
 621                 else
 622                         local newpos = backwards and range.start + (ndeleted <= 0 and ndeleted or 0) or (range.finish - ndeleted)
 623                         if refmt then
 624                                 local r = {start = newpos, finish = newpos}
 625                                 return refmt_at(big_enough_parent(range.start, range.finish - ndeleted), r, true)
 626                         end
 627                         return newpos
 628                 end
 629         end
 630
 631         local function insert_pair(range, delimiter, shiftless, auto_square)
 632                 local indices, nodes = walker.sexp_path(range)
 633                 local sexp = nodes[#nodes]
 634                 local right_after_prefix = sexp and sexp.p and range.start == sexp.start + #sexp.p
 635                 -- XXX: here I assume that # is a valid prefix for the dialect
 636                 local mb_closing = (delimiter == "|") and right_after_prefix and parser.opposite[sexp.p .. delimiter]
 637                 local closing = mb_closing or parser.opposite[delimiter]
 638                 local squarewords = fmt.squarewords
 639                 if squarewords and not right_after_prefix
 640                         and not (closing == "]" and shiftless and not auto_square)
 641                         and (auto_square or squarewords.not_optional)
 642                         and not fmt:adjust_bracket_p(indices, nodes, range) then
 643                                 delimiter, closing = "[", "]"
 644                 end
 645                 write(range.finish, closing)
 646                 write(range.start, delimiter)
 647                 if right_after_prefix or parser.tree.is_parsed(range.start) then
 648                         parser.tree.rewind(right_after_prefix and sexp.start or range.start)
 649                 end
 650                 return range.start + #delimiter
 651         end
 652
 653         local function make_wrap(kind)
 654                 return function(range, pos, shiftless, auto_square)
 655                         local opening = shiftless and swap[kind] or kind
 656                         local function _wrap(r)
 657                                 if not (r.finish > r.start) then return end
 658                                 insert_pair(r, opening, false, auto_square)
 659                         end
 660                         local action = {kill = false, wrap = false, splice = false, func = _wrap}
 661                         pick_out(range, pos, action)
 662                         local rangeng = {start = pos + #opening, finish = range.finish}
 663                         local _, parentng = walker.sexp_at(range)  -- TODO: range.finish is wrong. use sexp_path and big_enough_parent
 664                         return refmt_at(parentng, rangeng)
 665                 end
 666         end
 667
 668         local function newline(parent, range)
 669                 local line_comment = parent.is_line_comment
 670                 -- do not autoextend margin comments:
 671                 if line_comment and range.start < parent.finish + (parent.indent and 1 or 0)  then
 672                         local newpos = split_sexp(range)
 673                         if newpos then
 674                                 return newpos
 675                         end
 676                 end
 677                 if not parent.is_list and not line_comment then
 678                         -- if parent[#parent + 1] is nil, we are at EOF
 679                         if not parent.is_root or parent.is_parsed(range.start) or parent[#parent + 1] then
 680                                 parser.tree.rewind(parent.start or range.start)
 681                         end
 682                         local newpos = range.start
 683                         write(newpos, "\n")
 684                         return newpos + 1
 685                 end
 686                 if not parent.is_list then
 687                         local _
 688                         _, parent = walker.sexp_at(parent, true)
 689                 end
 690                 local last_nonblank_in_list = not parent.is_empty and parent[#parent].finish - (line_comment and 1 or 0)
 691                 local nxt = parent.after(range.start, startof)
 692                 local last_on_line = range.start == eol_at(range.start)
 693                 local margin = nxt and not nxt.indent and nxt.is_line_comment and nxt.finish
 694                 local after_last = last_nonblank_in_list and range.start > last_nonblank_in_list
 695                 local in_indent = nxt and nxt.indent and range.start <= nxt.start and range.start >= (nxt.start - nxt.indent)
 696                 local placeholder = "asdf"
 697                 local newpos = margin or range.start
 698                 if not parent.is_empty then
 699                         if in_indent then
 700                                 write(newpos, (placeholder.."\n"))
 701                         else
 702                                 write(newpos, "\n"..((after_last or last_on_line or margin) and placeholder or ""))
 703                         end
 704                 end
 705                 parser.tree.rewind(parent.start or newpos)
 706                 -- move the cursor onto the placeholder, so refmt_at can restore the position:
 707                 local r = {start = newpos, finish = newpos}
 708                 newpos = walker.start_after(r) or newpos
 709                 local rangeng = {start = newpos, finish = newpos}
 710                 newpos = refmt_at(parent, rangeng)
 711                 local _, parentng = walker.sexp_at({start = newpos, finish = newpos}, true)
 712                 if after_last then
 713                         local autoindent = parentng[#parentng].indent
 714                         write(parentng.finish, "\n"..string.rep(" ", autoindent or 0))
 715                 end
 716                 if after_last or last_on_line or margin or in_indent then
 717                         delete(newpos, #placeholder)
 718                 end
 719                 parser.tree.rewind(parentng.start or newpos)
 720                 return newpos
 721         end
 722
 723         local function close_and_newline(range, closing)
 724                 local opening = closing and parser.opposite[closing]
 725                 local parent = walker.quasilist_at(range, opening)
 726                 if parent then
 727                         local has_eol = parent.is_line_comment
 728                         local r = {start = parent.finish, finish = parent.finish}
 729                         local newpos = refmt_at(parent, r)
 730                         r = {start = newpos + (has_eol and 0 or 1), finish = newpos + (has_eol and 0 or 1)}
 731                         local list, parentng = walker.sexp_at(r)
 732                         newpos = list and list.finish + 1 or r.start
 733                         newpos = newline(parentng, {start = newpos, finish = newpos})
 734                         if not newpos then
 735                                 newpos = r.finish + 1
 736                                 write(newpos, "\n")
 737                                 parser.tree.rewind(parentng.start or list.start)
 738                         end
 739                         return newpos
 740                 elseif closing == "\n" then
 741                         local eol = eol_at(range.start)
 742                         local _, parentng = walker.sexp_at({start = eol, finish = eol})
 743                         local newpos = newline(parentng, {start = eol, finish = eol})
 744                         return newpos
 745                 end
 746                 return range.start
 747         end
 748
 749         local function join_line(_, pos)
 750                 local eol = eol_at(pos)
 751                 local r = {start = eol, finish = eol + 1}
 752                 return delete_nonsplicing(r, r.start, delete)
 753         end
 754
 755         local wrap_doublequote = make_wrap'"'
 756
 757         local function meta_doublequote(range, pos, auto_square)
 758                 local escaped = walker.escaped_at(range)
 759                 if not escaped then
 760                         return wrap_doublequote(range, pos, nil, auto_square)
 761                 elseif escaped.is_string then
 762                         return close_and_newline(range, '"')
 763                 end
 764                 return pos
 765         end
 766
 767         local block_comment_start
 768         for o, c in pairs(parser.opposite) do
 769                 if #c > 1 then
 770                         block_comment_start = o
 771                         break
 772                 end
 773         end
 774
 775         local wrap_comment = make_wrap(block_comment_start)
 776
 777         return {
 778                 delete_splicing = delete_splicing,
 779                 delete_nonsplicing = delete_nonsplicing,
 780                 refmt_at = refmt_at,
 781                 pick_out = pick_out,
 782                 raise_sexp = raise_sexp,
 783                 slurp_sexp = slurp_sexp,
 784                 barf_sexp = barf_sexp,
 785                 splice_sexp = splice_sexp,
 786                 wrap_round = make_wrap"(",
 787                 wrap_square = make_wrap"[",
 788                 wrap_curly = make_wrap"{",
 789                 meta_doublequote = meta_doublequote,
 790                 wrap_comment = wrap_comment,
 791                 insert_pair = insert_pair,
 792                 newline = newline,
 793                 join_line = join_line,
 794                 close_and_newline = close_and_newline,
 795                 cycle_wrap = cycle_wrap,
 796                 split_sexp = split_sexp,
 797                 join_sexps = join_sexps,
 798                 transpose_sexps = transpose_sexps,
 799                 transpose_words = transpose_words,
 800                 transpose_chars = transpose_chars,
 801         }
 802 end
 803
 804 return M