C4/HoldsQueue.pm

   1 package C4::HoldsQueue;
   2
   3 # Copyright 2011 Catalyst IT
   4 #
   5 # This file is part of Koha.
   6 #
   7 # Koha is free software; you can redistribute it and/or modify it
   8 # under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; either version 3 of the License, or
  10 # (at your option) any later version.
  11 #
  12 # Koha is distributed in the hope that it will be useful, but
  13 # WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with Koha; if not, see <http://www.gnu.org/licenses>.
  19
  20 # FIXME: expand perldoc, explain intended logic
  21
  22 use strict;
  23 use warnings;
  24
  25 use C4::Context;
  26 use C4::Search;
  27 use C4::Items;
  28 use C4::Branch;
  29 use C4::Circulation;
  30 use C4::Members;
  31 use C4::Biblio;
  32
  33 use List::Util qw(shuffle);
  34 use List::MoreUtils qw(any);
  35 use Data::Dumper;
  36
  37 use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);
  38 BEGIN {
  39     $VERSION = 3.03;
  40     require Exporter;
  41     @ISA = qw(Exporter);
  42     @EXPORT_OK = qw(
  43         &CreateQueue
  44         &GetHoldsQueueItems
  45
  46         &TransportCostMatrix
  47         &UpdateTransportCostMatrix
  48      );
  49 }
  50
  51
  52 =head1 FUNCTIONS
  53
  54 =head2 TransportCostMatrix
  55
  56   TransportCostMatrix();
  57
  58 Returns Transport Cost Matrix as a hashref <to branch code> => <from branch code> => cost
  59
  60 =cut
  61
  62 sub TransportCostMatrix {
  63     my $dbh   = C4::Context->dbh;
  64     my $transport_costs = $dbh->selectall_arrayref("SELECT * FROM transport_cost",{ Slice => {} });
  65
  66     my %transport_cost_matrix;
  67     foreach (@$transport_costs) {
  68         my $from = $_->{frombranch};
  69         my $to = $_->{tobranch};
  70         my $cost = $_->{cost};
  71         my $disabled = $_->{disable_transfer};
  72         $transport_cost_matrix{$to}{$from} = { cost => $cost, disable_transfer => $disabled };
  73     }
  74     return \%transport_cost_matrix;
  75 }
  76
  77 =head2 UpdateTransportCostMatrix
  78
  79   UpdateTransportCostMatrix($records);
  80
  81 Updates full Transport Cost Matrix table. $records is an arrayref of records.
  82 Records: { frombranch => <code>, tobranch => <code>, cost => <figure>, disable_transfer => <0,1> }
  83
  84 =cut
  85
  86 sub UpdateTransportCostMatrix {
  87     my ($records) = @_;
  88     my $dbh   = C4::Context->dbh;
  89
  90     my $sth = $dbh->prepare("INSERT INTO transport_cost (frombranch, tobranch, cost, disable_transfer) VALUES (?, ?, ?, ?)");
  91
  92     $dbh->do("TRUNCATE TABLE transport_cost");
  93     foreach (@$records) {
  94         my $cost = $_->{cost};
  95         my $from = $_->{frombranch};
  96         my $to = $_->{tobranch};
  97         if ($_->{disable_transfer}) {
  98             $cost ||= 0;
  99         }
 100         elsif ( !defined ($cost) || ($cost !~ m/(0|[1-9][0-9]*)(\.[0-9]*)?/o) ) {
 101             warn  "Invalid $from -> $to cost $cost - must be a number >= 0, disablig";
 102             $cost = 0;
 103             $_->{disable_transfer} = 1;
 104         }
 105         $sth->execute( $from, $to, $cost, $_->{disable_transfer} ? 1 : 0 );
 106     }
 107 }
 108
 109 =head2 GetHoldsQueueItems
 110
 111   GetHoldsQueueItems($branch);
 112
 113 Returns hold queue for a holding branch. If branch is omitted, then whole queue is returned
 114
 115 =cut
 116
 117 sub GetHoldsQueueItems {
 118     my ($branchlimit) = @_;
 119     my $dbh   = C4::Context->dbh;
 120
 121     my @bind_params = ();
 122     my $query = q/SELECT tmp_holdsqueue.*, biblio.author, items.ccode, items.itype, biblioitems.itemtype, items.location, items.enumchron, items.cn_sort, biblioitems.publishercode,biblio.copyrightdate,biblioitems.publicationyear,biblioitems.pages,biblioitems.size,biblioitems.publicationyear,biblioitems.isbn,items.copynumber
 123                   FROM tmp_holdsqueue
 124                        JOIN biblio      USING (biblionumber)
 125                   LEFT JOIN biblioitems USING (biblionumber)
 126                   LEFT JOIN items       USING (  itemnumber)
 127                 /;
 128     if ($branchlimit) {
 129         $query .=" WHERE tmp_holdsqueue.holdingbranch = ?";
 130         push @bind_params, $branchlimit;
 131     }
 132     $query .= " ORDER BY ccode, location, cn_sort, author, title, pickbranch, reservedate";
 133     my $sth = $dbh->prepare($query);
 134     $sth->execute(@bind_params);
 135     my $items = [];
 136     while ( my $row = $sth->fetchrow_hashref ){
 137         my $record = GetMarcBiblio($row->{biblionumber});
 138         if ($record){
 139             $row->{subtitle} = [ map { $_->{subfield} } @{ GetRecordValue( 'subtitle', $record, '' ) } ];
 140             $row->{parts} = GetRecordValue('parts',$record,'')->[0]->{subfield};
 141             $row->{numbers} = GetRecordValue('numbers',$record,'')->[0]->{subfield};
 142         }
 143
 144         # return the bib-level or item-level itype per syspref
 145         if (!C4::Context->preference('item-level_itypes')) {
 146             $row->{itype} = $row->{itemtype};
 147         }
 148         delete $row->{itemtype};
 149
 150         push @$items, $row;
 151     }
 152     return $items;
 153 }
 154
 155 =head2 CreateQueue
 156
 157   CreateQueue();
 158
 159 Top level function that turns reserves into tmp_holdsqueue and hold_fill_targets.
 160
 161 =cut
 162
 163 sub CreateQueue {
 164     my $dbh   = C4::Context->dbh;
 165
 166     $dbh->do("DELETE FROM tmp_holdsqueue");  # clear the old table for new info
 167     $dbh->do("DELETE FROM hold_fill_targets");
 168
 169     my $total_bibs            = 0;
 170     my $total_requests        = 0;
 171     my $total_available_items = 0;
 172     my $num_items_mapped      = 0;
 173
 174     my $branches_to_use;
 175     my $transport_cost_matrix;
 176     my $use_transport_cost_matrix = C4::Context->preference("UseTransportCostMatrix");
 177     if ($use_transport_cost_matrix) {
 178         $transport_cost_matrix = TransportCostMatrix();
 179         unless (keys %$transport_cost_matrix) {
 180             warn "UseTransportCostMatrix set to yes, but matrix not populated";
 181             undef $transport_cost_matrix;
 182         }
 183     }
 184     unless ($transport_cost_matrix) {
 185         $branches_to_use = load_branches_to_pull_from();
 186     }
 187
 188     my $bibs_with_pending_requests = GetBibsWithPendingHoldRequests();
 189
 190     foreach my $biblionumber (@$bibs_with_pending_requests) {
 191         $total_bibs++;
 192         my $hold_requests   = GetPendingHoldRequestsForBib($biblionumber);
 193         my $available_items = GetItemsAvailableToFillHoldRequestsForBib($biblionumber, $branches_to_use);
 194         $total_requests        += scalar(@$hold_requests);
 195         $total_available_items += scalar(@$available_items);
 196
 197         my $item_map = MapItemsToHoldRequests($hold_requests, $available_items, $branches_to_use, $transport_cost_matrix);
 198         $item_map  or next;
 199         my $item_map_size = scalar(keys %$item_map)
 200           or next;
 201
 202         $num_items_mapped += $item_map_size;
 203         CreatePicklistFromItemMap($item_map);
 204         AddToHoldTargetMap($item_map);
 205         if (($item_map_size < scalar(@$hold_requests  )) and
 206             ($item_map_size < scalar(@$available_items))) {
 207             # DOUBLE CHECK, but this is probably OK - unfilled item-level requests
 208             # FIXME
 209             #warn "unfilled requests for $biblionumber";
 210             #warn Dumper($hold_requests), Dumper($available_items), Dumper($item_map);
 211         }
 212     }
 213 }
 214
 215 =head2 GetBibsWithPendingHoldRequests
 216
 217   my $biblionumber_aref = GetBibsWithPendingHoldRequests();
 218
 219 Return an arrayref of the biblionumbers of all bibs
 220 that have one or more unfilled hold requests.
 221
 222 =cut
 223
 224 sub GetBibsWithPendingHoldRequests {
 225     my $dbh = C4::Context->dbh;
 226
 227     my $bib_query = "SELECT DISTINCT biblionumber
 228                      FROM reserves
 229                      WHERE found IS NULL
 230                      AND priority > 0
 231                      AND reservedate <= CURRENT_DATE()
 232                      AND suspend = 0
 233                      ";
 234     my $sth = $dbh->prepare($bib_query);
 235
 236     $sth->execute();
 237     my $biblionumbers = $sth->fetchall_arrayref();
 238
 239     return [ map { $_->[0] } @$biblionumbers ];
 240 }
 241
 242 =head2 GetPendingHoldRequestsForBib
 243
 244   my $requests = GetPendingHoldRequestsForBib($biblionumber);
 245
 246 Returns an arrayref of hashrefs to pending, unfilled hold requests
 247 on the bib identified by $biblionumber.  The following keys
 248 are present in each hashref:
 249
 250     biblionumber
 251     borrowernumber
 252     itemnumber
 253     priority
 254     branchcode
 255     reservedate
 256     reservenotes
 257     borrowerbranch
 258
 259 The arrayref is sorted in order of increasing priority.
 260
 261 =cut
 262
 263 sub GetPendingHoldRequestsForBib {
 264     my $biblionumber = shift;
 265
 266     my $dbh = C4::Context->dbh;
 267
 268     my $request_query = "SELECT biblionumber, borrowernumber, itemnumber, priority, reserves.branchcode,
 269                                 reservedate, reservenotes, borrowers.branchcode AS borrowerbranch
 270                          FROM reserves
 271                          JOIN borrowers USING (borrowernumber)
 272                          WHERE biblionumber = ?
 273                          AND found IS NULL
 274                          AND priority > 0
 275                          AND reservedate <= CURRENT_DATE()
 276                          AND suspend = 0
 277                          ORDER BY priority";
 278     my $sth = $dbh->prepare($request_query);
 279     $sth->execute($biblionumber);
 280
 281     my $requests = $sth->fetchall_arrayref({});
 282     return $requests;
 283
 284 }
 285
 286 =head2 GetItemsAvailableToFillHoldRequestsForBib
 287
 288   my $available_items = GetItemsAvailableToFillHoldRequestsForBib($biblionumber, $branches_ar);
 289
 290 Returns an arrayref of items available to fill hold requests
 291 for the bib identified by C<$biblionumber>.  An item is available
 292 to fill a hold request if and only if:
 293
 294     * it is not on loan
 295     * it is not withdrawn
 296     * it is not marked notforloan
 297     * it is not currently in transit
 298     * it is not lost
 299     * it is not sitting on the hold shelf
 300     * it is not damaged (unless AllowHoldsOnDamagedItems is on)
 301
 302 =cut
 303
 304 sub GetItemsAvailableToFillHoldRequestsForBib {
 305     my ($biblionumber, $branches_to_use) = @_;
 306
 307     my $dbh = C4::Context->dbh;
 308     my $items_query = "SELECT itemnumber, homebranch, holdingbranch, itemtypes.itemtype AS itype
 309                        FROM items ";
 310
 311     if (C4::Context->preference('item-level_itypes')) {
 312         $items_query .=   "LEFT JOIN itemtypes ON (itemtypes.itemtype = items.itype) ";
 313     } else {
 314         $items_query .=   "JOIN biblioitems USING (biblioitemnumber)
 315                            LEFT JOIN itemtypes USING (itemtype) ";
 316     }
 317     $items_query .=   "WHERE items.notforloan = 0
 318                        AND holdingbranch IS NOT NULL
 319                        AND itemlost = 0
 320                        AND withdrawn = 0";
 321     $items_query .= "  AND damaged = 0" unless C4::Context->preference('AllowHoldsOnDamagedItems');
 322     $items_query .= "  AND items.onloan IS NULL
 323                        AND (itemtypes.notforloan IS NULL OR itemtypes.notforloan = 0)
 324                        AND itemnumber NOT IN (
 325                            SELECT itemnumber
 326                            FROM reserves
 327                            WHERE biblionumber = ?
 328                            AND itemnumber IS NOT NULL
 329                            AND (found IS NOT NULL OR priority = 0)
 330                         )
 331                        AND items.biblionumber = ?";
 332
 333     my @params = ($biblionumber, $biblionumber);
 334     if ($branches_to_use && @$branches_to_use) {
 335         $items_query .= " AND holdingbranch IN (" . join (",", map { "?" } @$branches_to_use) . ")";
 336         push @params, @$branches_to_use;
 337     }
 338     my $sth = $dbh->prepare($items_query);
 339     $sth->execute(@params);
 340
 341     my $itm = $sth->fetchall_arrayref({});
 342     my @items = grep { ! scalar GetTransfers($_->{itemnumber}) } @$itm;
 343     return [ grep {
 344         my $rule = GetBranchItemRule($_->{homebranch}, $_->{itype});
 345         $_->{holdallowed} = $rule->{holdallowed};
 346     } @items ];
 347 }
 348
 349 =head2 MapItemsToHoldRequests
 350
 351   MapItemsToHoldRequests($hold_requests, $available_items, $branches, $transport_cost_matrix)
 352
 353 =cut
 354
 355 sub MapItemsToHoldRequests {
 356     my ($hold_requests, $available_items, $branches_to_use, $transport_cost_matrix) = @_;
 357
 358     # handle trival cases
 359     return unless scalar(@$hold_requests) > 0;
 360     return unless scalar(@$available_items) > 0;
 361
 362     # identify item-level requests
 363     my %specific_items_requested = map { $_->{itemnumber} => 1 }
 364                                    grep { defined($_->{itemnumber}) }
 365                                    @$hold_requests;
 366
 367     # group available items by itemnumber
 368     my %items_by_itemnumber = map { $_->{itemnumber} => $_ } @$available_items;
 369
 370     # items already allocated
 371     my %allocated_items = ();
 372
 373     # map of items to hold requests
 374     my %item_map = ();
 375
 376     # figure out which item-level requests can be filled
 377     my $num_items_remaining = scalar(@$available_items);
 378     foreach my $request (@$hold_requests) {
 379         last if $num_items_remaining == 0;
 380
 381         # is this an item-level request?
 382         if (defined($request->{itemnumber})) {
 383             # fill it if possible; if not skip it
 384             if (exists $items_by_itemnumber{$request->{itemnumber}} and
 385                 not exists $allocated_items{$request->{itemnumber}}) {
 386                 $item_map{$request->{itemnumber}} = {
 387                     borrowernumber => $request->{borrowernumber},
 388                     biblionumber => $request->{biblionumber},
 389                     holdingbranch =>  $items_by_itemnumber{$request->{itemnumber}}->{holdingbranch},
 390                     pickup_branch => $request->{branchcode} || $request->{borrowerbranch},
 391                     item_level => 1,
 392                     reservedate => $request->{reservedate},
 393                     reservenotes => $request->{reservenotes},
 394                 };
 395                 $allocated_items{$request->{itemnumber}}++;
 396                 $num_items_remaining--;
 397             }
 398         } else {
 399             # it's title-level request that will take up one item
 400             $num_items_remaining--;
 401         }
 402     }
 403
 404     # group available items by branch
 405     my %items_by_branch = ();
 406     foreach my $item (@$available_items) {
 407         next unless $item->{holdallowed};
 408
 409         push @{ $items_by_branch{ $item->{holdingbranch} } }, $item
 410           unless exists $allocated_items{ $item->{itemnumber} };
 411     }
 412     return \%item_map unless keys %items_by_branch;
 413
 414     # now handle the title-level requests
 415     $num_items_remaining = scalar(@$available_items) - scalar(keys %allocated_items);
 416     my $pull_branches;
 417     foreach my $request (@$hold_requests) {
 418         last if $num_items_remaining == 0;
 419         next if defined($request->{itemnumber}); # already handled these
 420
 421         # look for local match first
 422         my $pickup_branch = $request->{branchcode} || $request->{borrowerbranch};
 423         my ($itemnumber, $holdingbranch);
 424
 425         my $holding_branch_items = $items_by_branch{$pickup_branch};
 426         if ( $holding_branch_items ) {
 427             foreach my $item (@$holding_branch_items) {
 428                 if ( $request->{borrowerbranch} eq $item->{homebranch} ) {
 429                     $itemnumber = $item->{itemnumber};
 430                     last;
 431                 }
 432             }
 433             $holdingbranch = $pickup_branch;
 434         }
 435         elsif ($transport_cost_matrix) {
 436             $pull_branches = [keys %items_by_branch];
 437             $holdingbranch = least_cost_branch( $pickup_branch, $pull_branches, $transport_cost_matrix );
 438             if ( $holdingbranch ) {
 439
 440                 my $holding_branch_items = $items_by_branch{$holdingbranch};
 441                 foreach my $item (@$holding_branch_items) {
 442                     next if $request->{borrowerbranch} ne $item->{homebranch};
 443
 444                     $itemnumber = $item->{itemnumber};
 445                     last;
 446                 }
 447             }
 448             else {
 449                 warn "No transport costs for $pickup_branch";
 450             }
 451         }
 452
 453         unless ($itemnumber) {
 454             # not found yet, fall back to basics
 455             if ($branches_to_use) {
 456                 $pull_branches = $branches_to_use;
 457             } else {
 458                 $pull_branches = [keys %items_by_branch];
 459             }
 460
 461             # Try picking items where the home and pickup branch match first
 462             PULL_BRANCHES:
 463             foreach my $branch (@$pull_branches) {
 464                 my $holding_branch_items = $items_by_branch{$branch}
 465                   or next;
 466
 467                 $holdingbranch ||= $branch;
 468                 foreach my $item (@$holding_branch_items) {
 469                     next if $pickup_branch ne $item->{homebranch};
 470                     next if ( $item->{holdallowed} == 1 && $item->{homebranch} ne $request->{borrowerbranch} );
 471
 472                     $itemnumber = $item->{itemnumber};
 473                     $holdingbranch = $branch;
 474                     last PULL_BRANCHES;
 475                 }
 476             }
 477
 478             # Now try items from the least cost branch based on the transport cost matrix or StaticHoldsQueueWeight
 479             unless ( $itemnumber ) {
 480                 foreach my $current_item ( @{ $items_by_branch{$holdingbranch} } ) {
 481                     if ( $holdingbranch && ( $current_item->{holdallowed} == 2 || $request->{borrowerbranch} eq $current_item->{homebranch} ) ) {
 482                         $itemnumber = $current_item->{itemnumber};
 483                         last; # quit this loop as soon as we have a suitable item
 484                     }
 485                 }
 486             }
 487
 488             # Now try for items for any item that can fill this hold
 489             unless ( $itemnumber ) {
 490                 PULL_BRANCHES2:
 491                 foreach my $branch (@$pull_branches) {
 492                     my $holding_branch_items = $items_by_branch{$branch}
 493                       or next;
 494
 495                     foreach my $item (@$holding_branch_items) {
 496                         next if ( $item->{holdallowed} == 1 && $item->{homebranch} ne $request->{borrowerbranch} );
 497
 498                         $itemnumber = $item->{itemnumber};
 499                         $holdingbranch = $branch;
 500                         last PULL_BRANCHES2;
 501                     }
 502                 }
 503             }
 504         }
 505
 506         if ($itemnumber) {
 507             my $holding_branch_items = $items_by_branch{$holdingbranch}
 508               or die "Have $itemnumber, $holdingbranch, but no items!";
 509             @$holding_branch_items = grep { $_->{itemnumber} != $itemnumber } @$holding_branch_items;
 510             delete $items_by_branch{$holdingbranch} unless @$holding_branch_items;
 511
 512             $item_map{$itemnumber} = {
 513                 borrowernumber => $request->{borrowernumber},
 514                 biblionumber => $request->{biblionumber},
 515                 holdingbranch => $holdingbranch,
 516                 pickup_branch => $pickup_branch,
 517                 item_level => 0,
 518                 reservedate => $request->{reservedate},
 519                 reservenotes => $request->{reservenotes},
 520             };
 521             $num_items_remaining--;
 522         }
 523     }
 524     return \%item_map;
 525 }
 526
 527 =head2 CreatePickListFromItemMap
 528
 529 =cut
 530
 531 sub CreatePicklistFromItemMap {
 532     my $item_map = shift;
 533
 534     my $dbh = C4::Context->dbh;
 535
 536     my $sth_load=$dbh->prepare("
 537         INSERT INTO tmp_holdsqueue (biblionumber,itemnumber,barcode,surname,firstname,phone,borrowernumber,
 538                                     cardnumber,reservedate,title, itemcallnumber,
 539                                     holdingbranch,pickbranch,notes, item_level_request)
 540         VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)
 541     ");
 542
 543     foreach my $itemnumber  (sort keys %$item_map) {
 544         my $mapped_item = $item_map->{$itemnumber};
 545         my $biblionumber = $mapped_item->{biblionumber};
 546         my $borrowernumber = $mapped_item->{borrowernumber};
 547         my $pickbranch = $mapped_item->{pickup_branch};
 548         my $holdingbranch = $mapped_item->{holdingbranch};
 549         my $reservedate = $mapped_item->{reservedate};
 550         my $reservenotes = $mapped_item->{reservenotes};
 551         my $item_level = $mapped_item->{item_level};
 552
 553         my $item = GetItem($itemnumber);
 554         my $barcode = $item->{barcode};
 555         my $itemcallnumber = $item->{itemcallnumber};
 556
 557         my $borrower = GetMember('borrowernumber'=>$borrowernumber);
 558         my $cardnumber = $borrower->{'cardnumber'};
 559         my $surname = $borrower->{'surname'};
 560         my $firstname = $borrower->{'firstname'};
 561         my $phone = $borrower->{'phone'};
 562
 563         my $bib = GetBiblioData($biblionumber);
 564         my $title = $bib->{title};
 565
 566         $sth_load->execute($biblionumber, $itemnumber, $barcode, $surname, $firstname, $phone, $borrowernumber,
 567                            $cardnumber, $reservedate, $title, $itemcallnumber,
 568                            $holdingbranch, $pickbranch, $reservenotes, $item_level);
 569     }
 570 }
 571
 572 =head2 AddToHoldTargetMap
 573
 574 =cut
 575
 576 sub AddToHoldTargetMap {
 577     my $item_map = shift;
 578
 579     my $dbh = C4::Context->dbh;
 580
 581     my $insert_sql = q(
 582         INSERT INTO hold_fill_targets (borrowernumber, biblionumber, itemnumber, source_branchcode, item_level_request)
 583                                VALUES (?, ?, ?, ?, ?)
 584     );
 585     my $sth_insert = $dbh->prepare($insert_sql);
 586
 587     foreach my $itemnumber (keys %$item_map) {
 588         my $mapped_item = $item_map->{$itemnumber};
 589         $sth_insert->execute($mapped_item->{borrowernumber}, $mapped_item->{biblionumber}, $itemnumber,
 590                              $mapped_item->{holdingbranch}, $mapped_item->{item_level});
 591     }
 592 }
 593
 594 # Helper functions, not part of any interface
 595
 596 sub _trim {
 597     return $_[0] unless $_[0];
 598     $_[0] =~ s/^\s+//;
 599     $_[0] =~ s/\s+$//;
 600     $_[0];
 601 }
 602
 603 sub load_branches_to_pull_from {
 604     my $static_branch_list = C4::Context->preference("StaticHoldsQueueWeight")
 605       or return;
 606
 607     my @branches_to_use = map _trim($_), split /,/, $static_branch_list;
 608
 609     @branches_to_use = shuffle(@branches_to_use) if  C4::Context->preference("RandomizeHoldsQueueWeight");
 610
 611     return \@branches_to_use;
 612 }
 613
 614 sub least_cost_branch {
 615
 616     #$from - arrayref
 617     my ($to, $from, $transport_cost_matrix) = @_;
 618
 619     # Nothing really spectacular: supply to branch, a list of potential from branches
 620     # and find the minimum from - to value from the transport_cost_matrix
 621     return $from->[0] if @$from == 1;
 622
 623     # If the pickup library is in the list of libraries to pull from,
 624     # return that library right away, it is obviously the least costly
 625     return ($to) if any { $_ eq $to } @$from;
 626
 627     my ($least_cost, @branch);
 628     foreach (@$from) {
 629         my $cell = $transport_cost_matrix->{$to}{$_};
 630         next if $cell->{disable_transfer};
 631
 632         my $cost = $cell->{cost};
 633         next unless defined $cost; # XXX should this be reported?
 634
 635         unless (defined $least_cost) {
 636             $least_cost = $cost;
 637             push @branch, $_;
 638             next;
 639         }
 640
 641         next if $cost > $least_cost;
 642
 643         if ($cost == $least_cost) {
 644             push @branch, $_;
 645             next;
 646         }
 647
 648         @branch = ($_);
 649         $least_cost = $cost;
 650     }
 651
 652     return $branch[0];
 653
 654     # XXX return a random @branch with minimum cost instead of the first one;
 655     # return $branch[0] if @branch == 1;
 656 }
 657
 658
 659 1;