summaryrefslogtreecommitdiff
path: root/src/autoreplace_cmd.cpp
blob: c0483ff1cf97d10a4bca19eb7683b77f80c3d698 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
/* $Id$ */

/** @file autoreplace_cmd.cpp Deals with autoreplace execution but not the setup */

#include "stdafx.h"
#include "openttd.h"
#include "company_func.h"
#include "debug.h"
#include "vehicle_gui.h"
#include "train.h"
#include "aircraft.h"
#include "roadveh.h"
#include "rail.h"
#include "command_func.h"
#include "engine_base.h"
#include "engine_func.h"
#include "vehicle_func.h"
#include "functions.h"
#include "autoreplace_func.h"
#include "articulated_vehicles.h"
#include "core/alloc_func.hpp"

#include "table/strings.h"

/** Figure out if two engines got at least one type of cargo in common (refitting if needed)
 * @param engine_a one of the EngineIDs
 * @param engine_b the other EngineID
 * @param type the type of the engines
 * @return true if they can both carry the same type of cargo (or at least one of them got no capacity at all)
 */
static bool EnginesGotCargoInCommon(EngineID engine_a, EngineID engine_b, VehicleType type)
{
	uint32 available_cargos_a = GetUnionOfArticulatedRefitMasks(engine_a, type, true);
	uint32 available_cargos_b = GetUnionOfArticulatedRefitMasks(engine_b, type, true);
	return (available_cargos_a == 0 || available_cargos_b == 0 || (available_cargos_a & available_cargos_b) != 0);
}

/**
 * Checks some basic properties whether autoreplace is allowed
 * @param from Origin engine
 * @param to Destination engine
 * @param company Company to check for
 * @return true if autoreplace is allowed
 */
bool CheckAutoreplaceValidity(EngineID from, EngineID to, CompanyID company)
{
	/* First we make sure that it's a valid type the user requested
	 * check that it's an engine that is in the engine array */
	if (!IsEngineIndex(from) || !IsEngineIndex(to)) return false;

	/* we can't replace an engine into itself (that would be autorenew) */
	if (from == to) return false;

	VehicleType type = GetEngine(from)->type;

	/* check that the new vehicle type is available to the company and its type is the same as the original one */
	if (!IsEngineBuildable(to, type, company)) return false;

	switch (type) {
		case VEH_TRAIN: {
			const RailVehicleInfo *rvi_from = RailVehInfo(from);
			const RailVehicleInfo *rvi_to   = RailVehInfo(to);

			/* make sure the railtypes are compatible */
			if ((GetRailTypeInfo(rvi_from->railtype)->compatible_railtypes & GetRailTypeInfo(rvi_to->railtype)->compatible_railtypes) == 0) return false;

			/* make sure we do not replace wagons with engines or vise versa */
			if ((rvi_from->railveh_type == RAILVEH_WAGON) != (rvi_to->railveh_type == RAILVEH_WAGON)) return false;
			break;
		}

		case VEH_ROAD:
			/* make sure that we do not replace a tram with a normal road vehicles or vise versa */
			if (HasBit(EngInfo(from)->misc_flags, EF_ROAD_TRAM) != HasBit(EngInfo(to)->misc_flags, EF_ROAD_TRAM)) return false;
			break;

		case VEH_AIRCRAFT:
			/* make sure that we do not replace a plane with a helicopter or vise versa */
			if ((AircraftVehInfo(from)->subtype & AIR_CTOL) != (AircraftVehInfo(to)->subtype & AIR_CTOL)) return false;
			break;

		default: break;
	}

	/* the engines needs to be able to carry the same cargo */
	return EnginesGotCargoInCommon(from, to, type);
}

/** Transfer cargo from a single (articulated )old vehicle to the new vehicle chain
 * @param old_veh Old vehicle that will be sold
 * @param new_head Head of the completely constructed new vehicle chain
 * @param part_of_chain The vehicle is part of a train
 */
static void TransferCargo(Vehicle *old_veh, Vehicle *new_head, bool part_of_chain)
{
	assert(!part_of_chain || new_head->IsPrimaryVehicle());
	/* Loop through source parts */
	for (Vehicle *src = old_veh; src != NULL; src = src->Next()) {
		if (!part_of_chain && src->type == VEH_TRAIN && src != old_veh && src != old_veh->u.rail.other_multiheaded_part && !IsArticulatedPart(src)) {
			/* Skip vehicles, which do not belong to old_veh */
			src = GetLastEnginePart(src);
			continue;
		}
		if (src->cargo_type >= NUM_CARGO || src->cargo.Count() == 0) continue;

		/* Find free space in the new chain */
		for (Vehicle *dest = new_head; dest != NULL && src->cargo.Count() > 0; dest = dest->Next()) {
			if (!part_of_chain && dest->type == VEH_TRAIN && dest != new_head && dest != new_head->u.rail.other_multiheaded_part && !IsArticulatedPart(dest)) {
				/* Skip vehicles, which do not belong to new_head */
				dest = GetLastEnginePart(dest);
				continue;
			}
			if (dest->cargo_type != src->cargo_type) continue;

			uint amount = min(src->cargo.Count(), dest->cargo_cap - dest->cargo.Count());
			if (amount <= 0) continue;

			src->cargo.MoveTo(&dest->cargo, amount);
		}
	}

	/* Update train weight etc., the old vehicle will be sold anyway */
	if (part_of_chain && new_head->type == VEH_TRAIN) TrainConsistChanged(new_head, true);
}

/**
 * Tests whether refit orders that applied to v will also apply to the new vehicle type
 * @param v The vehicle to be replaced
 * @param engine_type The type we want to replace with
 * @return true iff all refit orders stay valid
 */
static bool VerifyAutoreplaceRefitForOrders(const Vehicle *v, EngineID engine_type)
{
	const Order *o;
	const Vehicle *u;

	uint32 union_refit_mask_a = GetUnionOfArticulatedRefitMasks(v->engine_type, v->type, false);
	uint32 union_refit_mask_b = GetUnionOfArticulatedRefitMasks(engine_type, v->type, false);

	if (v->type == VEH_TRAIN) {
		u = v->First();
	} else {
		u = v;
	}

	FOR_VEHICLE_ORDERS(u, o) {
		if (!o->IsRefit()) continue;
		CargoID cargo_type = o->GetRefitCargo();

		if (!HasBit(union_refit_mask_a, cargo_type)) continue;
		if (!HasBit(union_refit_mask_b, cargo_type)) return false;
	}

	return true;
}

/**
 * Function to find what type of cargo to refit to when autoreplacing
 * @param *v Original vehicle, that is being replaced
 * @param engine_type The EngineID of the vehicle that is being replaced to
 * @param part_of_chain The vehicle is part of a train
 * @return The cargo type to replace to
 *    CT_NO_REFIT is returned if no refit is needed
 *    CT_INVALID is returned when both old and new vehicle got cargo capacity and refitting the new one to the old one's cargo type isn't possible
 */
static CargoID GetNewCargoTypeForReplace(Vehicle *v, EngineID engine_type, bool part_of_chain)
{
	CargoID cargo_type;

	if (GetUnionOfArticulatedRefitMasks(engine_type, v->type, true) == 0) return CT_NO_REFIT; // Don't try to refit an engine with no cargo capacity

	if (IsArticulatedVehicleCarryingDifferentCargos(v, &cargo_type)) return CT_INVALID; // We cannot refit to mixed cargos in an automated way

	uint32 available_cargo_types = GetIntersectionOfArticulatedRefitMasks(engine_type, v->type, true);

	if (cargo_type == CT_INVALID) {
		if (v->type != VEH_TRAIN) return CT_NO_REFIT; // If the vehicle does not carry anything at all, every replacement is fine.

		if (!part_of_chain) return CT_NO_REFIT;

		/* the old engine didn't have cargo capacity, but the new one does
		 * now we will figure out what cargo the train is carrying and refit to fit this */

		for (v = v->First(); v != NULL; v = v->Next()) {
			if (v->cargo_cap == 0) continue;
			/* Now we found a cargo type being carried on the train and we will see if it is possible to carry to this one */
			if (HasBit(available_cargo_types, v->cargo_type)) {
				/* Do we have to refit the vehicle, or is it already carrying the right cargo? */
				uint16 *default_capacity = GetCapacityOfArticulatedParts(engine_type, v->type);
				for (CargoID cid = 0; cid < NUM_CARGO; cid++) {
					if (cid != v->cargo_type && default_capacity[cid] > 0) return v->cargo_type;
				}

				return CT_NO_REFIT;
			}
		}

		return CT_NO_REFIT; // We failed to find a cargo type on the old vehicle and we will not refit the new one
	} else {
		if (!HasBit(available_cargo_types, cargo_type)) return CT_INVALID; // We can't refit the vehicle to carry the cargo we want

		if (part_of_chain && !VerifyAutoreplaceRefitForOrders(v, engine_type)) return CT_INVALID; // Some refit orders lose their effect

		/* Do we have to refit the vehicle, or is it already carrying the right cargo? */
		uint16 *default_capacity = GetCapacityOfArticulatedParts(engine_type, v->type);
		for (CargoID cid = 0; cid < NUM_CARGO; cid++) {
			if (cid != cargo_type && default_capacity[cid] > 0) return cargo_type;
		}

		return CT_NO_REFIT;
	}
}

/** Get the EngineID of the replacement for a vehicle
 * @param v The vehicle to find a replacement for
 * @param c The vehicle's owner (it's faster to forward the pointer than refinding it)
 * @return the EngineID of the replacement. INVALID_ENGINE if no buildable replacement is found
 */
static EngineID GetNewEngineType(const Vehicle *v, const Company *c)
{
	assert(v->type != VEH_TRAIN || !IsArticulatedPart(v));

	if (v->type == VEH_TRAIN && IsRearDualheaded(v)) {
		/* we build the rear ends of multiheaded trains with the front ones */
		return INVALID_ENGINE;
	}

	EngineID e = EngineReplacementForCompany(c, v->engine_type, v->group_id);

	if (e != INVALID_ENGINE && IsEngineBuildable(e, v->type, _current_company)) {
		return e;
	}

	if (v->NeedsAutorenewing(c) && // replace if engine is too old
	    IsEngineBuildable(v->engine_type, v->type, _current_company)) { // engine can still be build
		return v->engine_type;
	}

	return INVALID_ENGINE;
}

/** Builds and refits a replacement vehicle
 * Important: The old vehicle is still in the original vehicle chain (used for determining the cargo when the old vehicle did not carry anything, but the new one does)
 * @param old_veh A single (articulated/multiheaded) vehicle that shall be replaced.
 * @param new_vehicle Returns the newly build and refittet vehicle
 * @param part_of_chain The vehicle is part of a train
 * @return cost or error
 */
static CommandCost BuildReplacementVehicle(Vehicle *old_veh, Vehicle **new_vehicle, bool part_of_chain)
{
	*new_vehicle = NULL;

	/* Shall the vehicle be replaced? */
	const Company *c = GetCompany(_current_company);
	EngineID e = GetNewEngineType(old_veh, c);
	if (e == INVALID_ENGINE) return CommandCost(); // neither autoreplace is set, nor autorenew is triggered

	/* Does it need to be refitted */
	CargoID refit_cargo = GetNewCargoTypeForReplace(old_veh, e, part_of_chain);
	if (refit_cargo == CT_INVALID) return CommandCost(); // incompatible cargos

	/* Build the new vehicle */
	CommandCost cost = DoCommand(old_veh->tile, e, 0, DC_EXEC | DC_AUTOREPLACE, GetCmdBuildVeh(old_veh));
	if (cost.Failed()) return cost;

	Vehicle *new_veh = GetVehicle(_new_vehicle_id);
	*new_vehicle = new_veh;

	/* Refit the vehicle if needed */
	if (refit_cargo != CT_NO_REFIT) {
		cost.AddCost(DoCommand(0, new_veh->index, refit_cargo, DC_EXEC, GetCmdRefitVeh(new_veh)));
		assert(cost.Succeeded()); // This should be ensured by GetNewCargoTypeForReplace()
	}

	/* Try to reverse the vehicle, but do not care if it fails as the new type might not be reversible */
	if (new_veh->type == VEH_TRAIN && HasBit(old_veh->u.rail.flags, VRF_REVERSE_DIRECTION)) {
		DoCommand(0, new_veh->index, true, DC_EXEC, CMD_REVERSE_TRAIN_DIRECTION);
	}

	return cost;
}

/** Issue a start/stop command
 * @param v a vehicle
 * @param evaluate_callback shall the start/stop callback be evaluated?
 * @return success or error
 */
static inline CommandCost StartStopVehicle(const Vehicle *v, bool evaluate_callback)
{
	return DoCommand(0, v->index, evaluate_callback ? 1 : 0, DC_EXEC | DC_AUTOREPLACE, CMD_START_STOP_VEHICLE);
}

/** Issue a train vehicle move command
 * @param v The vehicle to move
 * @param after The vehicle to insert 'v' after, or NULL to start new chain
 * @param whole_chain move all vehicles following 'v' (true), or only 'v' (false)
 * @return success or error
 */
static inline CommandCost MoveVehicle(const Vehicle *v, const Vehicle *after, uint32 flags, bool whole_chain)
{
	return DoCommand(0, v->index | (after != NULL ? after->index : INVALID_VEHICLE) << 16, whole_chain ? 1 : 0, flags, CMD_MOVE_RAIL_VEHICLE);
}

/** Copy head specific things to the new vehicle chain after it was successfully constructed
 * @param old_head The old front vehicle (no wagons attached anymore)
 * @param new_head The new head of the completely replaced vehicle chain
 * @param flags the command flags to use
 */
static CommandCost CopyHeadSpecificThings(Vehicle *old_head, Vehicle *new_head, uint32 flags)
{
	CommandCost cost = CommandCost();

	/* Share orders */
	if (cost.Succeeded() && old_head != new_head) cost.AddCost(DoCommand(0, (old_head->index << 16) | new_head->index, CO_SHARE, DC_EXEC, CMD_CLONE_ORDER));

	/* Copy group membership */
	if (cost.Succeeded() && old_head != new_head) cost.AddCost(DoCommand(0, old_head->group_id, new_head->index, DC_EXEC, CMD_ADD_VEHICLE_GROUP));

	/* Perform start/stop check whether the new vehicle suits newgrf restrictions etc. */
	if (cost.Succeeded()) {
		/* Start the vehicle, might be denied by certain things */
		assert((new_head->vehstatus & VS_STOPPED) != 0);
		cost.AddCost(StartStopVehicle(new_head, true));

		/* Stop the vehicle again, but do not care about evil newgrfs allowing starting but not stopping :p */
		if (cost.Succeeded()) cost.AddCost(StartStopVehicle(new_head, false));
	}

	/* Last do those things which do never fail (resp. we do not care about), but which are not undo-able */
	if (cost.Succeeded() && old_head != new_head && (flags & DC_EXEC) != 0) {
		/* Copy vehicle name */
		if (old_head->name != NULL) {
			DoCommand(0, new_head->index, 0, DC_EXEC | DC_AUTOREPLACE, CMD_RENAME_VEHICLE, old_head->name);
		}

		/* Copy other things which cannot be copied by a command and which shall not stay resetted from the build vehicle command */
		new_head->CopyVehicleConfigAndStatistics(old_head);

		/* Switch vehicle windows to the new vehicle, so they are not closed when the old vehicle is sold */
		ChangeVehicleViewWindow(old_head->index, new_head->index);
	}

	return cost;
}

/** Replace a single unit in a free wagon chain
 * @param single_unit vehicle to let autoreplace/renew operator on
 * @param flags command flags
 * @param wagon_removal remove wagons when the resulting chain occupies more tiles than the old did
 * @param nothing_to_do is set to 'false' when something was done (only valid when not failed)
 * @return cost or error
 */
static CommandCost ReplaceFreeUnit(Vehicle **single_unit, uint32 flags, bool *nothing_to_do)
{
	Vehicle *old_v = *single_unit;
	assert(old_v->type == VEH_TRAIN && !IsArticulatedPart(old_v) && !IsRearDualheaded(old_v));

	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);

	/* Build and refit replacement vehicle */
	Vehicle *new_v = NULL;
	cost.AddCost(BuildReplacementVehicle(old_v, &new_v, false));

	/* Was a new vehicle constructed? */
	if (cost.Succeeded() && new_v != NULL) {
		*nothing_to_do = false;

		if ((flags & DC_EXEC) != 0) {
			/* Move the new vehicle behind the old */
			MoveVehicle(new_v, old_v, DC_EXEC, false);

			/* Take over cargo
			 * Note: We do only transfer cargo from the old to the new vehicle.
			 *       I.e. we do not transfer remaining cargo to other vehicles.
			 *       Else you would also need to consider moving cargo to other free chains,
			 *       or doing the same in ReplaceChain(), which would be quite troublesome.
			 */
			TransferCargo(old_v, new_v, false);

			*single_unit = new_v;
		}

		/* Sell the old vehicle */
		cost.AddCost(DoCommand(0, old_v->index, 0, flags, GetCmdSellVeh(old_v)));

		/* If we are not in DC_EXEC undo everything */
		if ((flags & DC_EXEC) == 0) {
			DoCommand(0, new_v->index, 0, DC_EXEC, GetCmdSellVeh(new_v));
		}
	}

	return cost;
}

/** Replace a whole vehicle chain
 * @param chain vehicle chain to let autoreplace/renew operator on
 * @param flags command flags
 * @param wagon_removal remove wagons when the resulting chain occupies more tiles than the old did
 * @param nothing_to_do is set to 'false' when something was done (only valid when not failed)
 * @return cost or error
 */
static CommandCost ReplaceChain(Vehicle **chain, uint32 flags, bool wagon_removal, bool *nothing_to_do)
{
	Vehicle *old_head = *chain;
	assert(old_head->IsPrimaryVehicle());

	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);

	if (old_head->type == VEH_TRAIN) {
		/* Store the length of the old vehicle chain, rounded up to whole tiles */
		uint16 old_total_length = (old_head->u.rail.cached_total_length + TILE_SIZE - 1) / TILE_SIZE * TILE_SIZE;

		int num_units = 0; ///< Number of units in the chain
		for (Vehicle *w = old_head; w != NULL; w = GetNextUnit(w)) num_units++;

		Vehicle **old_vehs = CallocT<Vehicle *>(num_units); ///< Will store vehicles of the old chain in their order
		Vehicle **new_vehs = CallocT<Vehicle *>(num_units); ///< New vehicles corresponding to old_vehs or NULL if no replacement
		Money *new_costs = MallocT<Money>(num_units);       ///< Costs for buying and refitting the new vehicles

		/* Collect vehicles and build replacements
		 * Note: The replacement vehicles can only successfully build as long as the old vehicles are still in their chain */
		int i;
		Vehicle *w;
		for (w = old_head, i = 0; w != NULL; w = GetNextUnit(w), i++) {
			assert(i < num_units);
			old_vehs[i] = w;

			CommandCost ret = BuildReplacementVehicle(old_vehs[i], &new_vehs[i], true);
			cost.AddCost(ret);
			if (cost.Failed()) break;

			new_costs[i] = ret.GetCost();
			if (new_vehs[i] != NULL) *nothing_to_do = false;
		}
		Vehicle *new_head = (new_vehs[0] != NULL ? new_vehs[0] : old_vehs[0]);

		/* Note: When autoreplace has already failed here, old_vehs[] is not completely initialized. But it is also not needed. */
		if (cost.Succeeded()) {
			/* Separate the head, so we can start constructing the new chain */
			Vehicle *second = GetNextUnit(old_head);
			if (second != NULL) cost.AddCost(MoveVehicle(second, NULL, DC_EXEC | DC_AUTOREPLACE, true));

			assert(GetNextUnit(new_head) == NULL);

			/* Append engines to the new chain
			 * We do this from back to front, so that the head of the temporary vehicle chain does not change all the time.
			 * OTOH the vehicle attach callback is more expensive this way :s */
			Vehicle *last_engine = NULL; ///< Shall store the last engine unit after this step
			if (cost.Succeeded()) {
				for (int i = num_units - 1; i > 0; i--) {
					Vehicle *append = (new_vehs[i] != NULL ? new_vehs[i] : old_vehs[i]);

					if (RailVehInfo(append->engine_type)->railveh_type == RAILVEH_WAGON) continue;

					if (last_engine == NULL) last_engine = append;
					cost.AddCost(MoveVehicle(append, new_head, DC_EXEC, false));
					if (cost.Failed()) break;
				}
				if (last_engine == NULL) last_engine = new_head;
			}

			/* When wagon removal is enabled and the new engines without any wagons are already longer than the old, we have to fail */
			if (cost.Succeeded() && wagon_removal && new_head->u.rail.cached_total_length > old_total_length) cost = CommandCost(STR_TRAIN_TOO_LONG_AFTER_REPLACEMENT);

			/* Append/insert wagons into the new vehicle chain
			 * We do this from back to front, so we can stop when wagon removal or maximum train length (i.e. from mammoth-train setting) is triggered.
			 */
			if (cost.Succeeded()) {
				for (int i = num_units - 1; i > 0; i--) {
					assert(last_engine != NULL);
					Vehicle *append = (new_vehs[i] != NULL ? new_vehs[i] : old_vehs[i]);

					if (RailVehInfo(append->engine_type)->railveh_type == RAILVEH_WAGON) {
						/* Insert wagon after 'last_engine' */
						CommandCost res = MoveVehicle(append, last_engine, DC_EXEC, false);

						if (res.Succeeded() && wagon_removal && new_head->u.rail.cached_total_length > old_total_length) {
							MoveVehicle(append, NULL, DC_EXEC | DC_AUTOREPLACE, false);
							break;
						}

						cost.AddCost(res);
						if (cost.Failed()) break;
					} else {
						/* We have reached 'last_engine', continue with the next engine towards the front */
						assert(append == last_engine);
						last_engine = GetPrevUnit(last_engine);
					}
				}
			}

			/* Sell superfluous new vehicles that could not be inserted. */
			if (cost.Succeeded() && wagon_removal) {
				for (int i = 1; i < num_units; i++) {
					Vehicle *wagon = new_vehs[i];
					if (wagon == NULL) continue;
					if (wagon->First() == new_head) break;

					assert(RailVehInfo(wagon->engine_type)->railveh_type == RAILVEH_WAGON);

					/* Sell wagon */
					CommandCost ret = DoCommand(0, wagon->index, 0, DC_EXEC, GetCmdSellVeh(wagon));
					assert(ret.Succeeded());
					new_vehs[i] = NULL;

					/* Revert the money subtraction when the vehicle was built.
					 * This value is different from the sell value, esp. because of refitting */
					cost.AddCost(-new_costs[i]);
				}
			}

			/* The new vehicle chain is constructed, now take over orders and everything... */
			if (cost.Succeeded()) cost.AddCost(CopyHeadSpecificThings(old_head, new_head, flags));

			if (cost.Succeeded()) {
				/* Success ! */
				if ((flags & DC_EXEC) != 0 && new_head != old_head) {
					*chain = new_head;
				}

				/* Transfer cargo of old vehicles and sell them*/
				for (int i = 0; i < num_units; i++) {
					Vehicle *w = old_vehs[i];
					/* Is the vehicle again part of the new chain?
					 * Note: We cannot test 'new_vehs[i] != NULL' as wagon removal might cause to remove both */
					if (w->First() == new_head) continue;

					if ((flags & DC_EXEC) != 0) TransferCargo(w, new_head, true);

					cost.AddCost(DoCommand(0, w->index, 0, flags, GetCmdSellVeh(w)));
					if ((flags & DC_EXEC) != 0) {
						old_vehs[i] = NULL;
						if (i == 0) old_head = NULL;
					}
				}
			}

			/* If we are not in DC_EXEC undo everything, i.e. rearrange old vehicles.
			 * We do this from back to front, so that the head of the temporary vehicle chain does not change all the time.
			 * Note: The vehicle attach callback is disabled here :) */
			if ((flags & DC_EXEC) == 0) {
				/* Separate the head, so we can reattach the old vehicles */
				Vehicle *second = GetNextUnit(old_head);
				if (second != NULL) MoveVehicle(second, NULL, DC_EXEC | DC_AUTOREPLACE, true);

				assert(GetNextUnit(old_head) == NULL);

				for (int i = num_units - 1; i > 0; i--) {
					CommandCost ret = MoveVehicle(old_vehs[i], old_head, DC_EXEC | DC_AUTOREPLACE, false);
					assert(ret.Succeeded());
				}
			}
		}

		/* Finally undo buying of new vehicles */
		if ((flags & DC_EXEC) == 0) {
			for (int i = num_units - 1; i >= 0; i--) {
				if (new_vehs[i] != NULL) {
					DoCommand(0, new_vehs[i]->index, 0, DC_EXEC, GetCmdSellVeh(new_vehs[i]));
					new_vehs[i] = NULL;
				}
			}
		}

		free(old_vehs);
		free(new_vehs);
		free(new_costs);
	} else {
		/* Build and refit replacement vehicle */
		Vehicle *new_head = NULL;
		cost.AddCost(BuildReplacementVehicle(old_head, &new_head, true));

		/* Was a new vehicle constructed? */
		if (cost.Succeeded() && new_head != NULL) {
			*nothing_to_do = false;

			/* The new vehicle is constructed, now take over orders and everything... */
			cost.AddCost(CopyHeadSpecificThings(old_head, new_head, flags));

			if (cost.Succeeded()) {
				/* The new vehicle is constructed, now take over cargo */
				if ((flags & DC_EXEC) != 0) {
					TransferCargo(old_head, new_head, true);
					*chain = new_head;
				}

				/* Sell the old vehicle */
				cost.AddCost(DoCommand(0, old_head->index, 0, flags, GetCmdSellVeh(old_head)));
			}

			/* If we are not in DC_EXEC undo everything */
			if ((flags & DC_EXEC) == 0) {
				DoCommand(0, new_head->index, 0, DC_EXEC, GetCmdSellVeh(new_head));
			}
		}
	}

	return cost;
}

/** Autoreplaces a vehicle
 * Trains are replaced as a whole chain, free wagons in depot are replaced on their own
 * @param tile not used
 * @param flags type of operation
 * @param p1 Index of vehicle
 * @param p2 not used
 */
CommandCost CmdAutoreplaceVehicle(TileIndex tile, uint32 flags, uint32 p1, uint32 p2, const char *text)
{
	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);
	bool nothing_to_do = true;

	if (!IsValidVehicleID(p1)) return CMD_ERROR;
	Vehicle *v = GetVehicle(p1);
	if (!CheckOwnership(v->owner)) return CMD_ERROR;
	if (!v->IsInDepot()) return CMD_ERROR;
	if (HASBITS(v->vehstatus, VS_CRASHED)) return CMD_ERROR;

	bool free_wagon = false;
	if (v->type == VEH_TRAIN) {
		if (IsArticulatedPart(v) || IsRearDualheaded(v)) return CMD_ERROR;
		free_wagon = !IsFrontEngine(v);
		if (free_wagon && IsFrontEngine(v->First())) return CMD_ERROR;
	} else {
		if (!v->IsPrimaryVehicle()) return CMD_ERROR;
	}

	const Company *c = GetCompany(_current_company);
	bool wagon_removal = c->renew_keep_length;

	/* Test whether any replacement is set, before issuing a whole lot of commands that would end in nothing changed */
	Vehicle *w = v;
	bool any_replacements = false;
	while (w != NULL && !any_replacements) {
		any_replacements = (GetNewEngineType(w, c) != INVALID_ENGINE);
		w = (!free_wagon && w->type == VEH_TRAIN ? GetNextUnit(w) : NULL);
	}

	if (any_replacements) {
		bool was_stopped = free_wagon || ((v->vehstatus & VS_STOPPED) != 0);

		/* Stop the vehicle */
		if (!was_stopped) cost.AddCost(StartStopVehicle(v, true));
		if (cost.Failed()) return cost;

		assert(v->IsStoppedInDepot());

		/* We have to construct the new vehicle chain to test whether it is valid.
		 * Vehicle construction needs random bits, so we have to save the random seeds
		 * to prevent desyncs and to replay newgrf callbacks during DC_EXEC */
		SavedRandomSeeds saved_seeds;
		SaveRandomSeeds(&saved_seeds);
		if (free_wagon) {
			cost.AddCost(ReplaceFreeUnit(&v, flags & ~DC_EXEC, &nothing_to_do));
		} else {
			cost.AddCost(ReplaceChain(&v, flags & ~DC_EXEC, wagon_removal, &nothing_to_do));
		}
		RestoreRandomSeeds(saved_seeds);

		if (cost.Succeeded() && (flags & DC_EXEC) != 0) {
			CommandCost ret;
			if (free_wagon) {
				ret = ReplaceFreeUnit(&v, flags, &nothing_to_do);
			} else {
				ret = ReplaceChain(&v, flags, wagon_removal, &nothing_to_do);
			}
			assert(ret.Succeeded() && ret.GetCost() == cost.GetCost());
		}

		/* Restart the vehicle */
		if (!was_stopped) cost.AddCost(StartStopVehicle(v, false));
	}

	if (cost.Succeeded() && nothing_to_do) cost = CommandCost(STR_AUTOREPLACE_NOTHING_TO_DO);
	return cost;
}