summaryrefslogtreecommitdiff
path: root/src/engine.cpp
blob: d39c86f6aa0861aa0d54f627d8461379bff9ae43 (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
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
/* $Id$ */

/** @file engine.cpp Base for all engine handling. */

#include "stdafx.h"
#include "debug.h"
#include "company_func.h"
#include "command_func.h"
#include "news_func.h"
#include "variables.h"
#include "aircraft.h"
#include "newgrf_engine.h"
#include "group.h"
#include "strings_func.h"
#include "gfx_func.h"
#include "core/random_func.hpp"
#include "window_func.h"
#include "date_func.h"
#include "autoreplace_gui.h"
#include "string_func.h"
#include "ai/ai.hpp"
#include "vehicle_func.h"
#include "settings_type.h"
#include "core/pool_func.hpp"

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

EnginePool _engine_pool("Engine");
INSTANTIATE_POOL_METHODS(Engine)

EngineOverrideManager _engine_mngr;

/** Year that engine aging stops. Engines will not reduce in reliability
 * and no more engines will be introduced */
Year _year_engine_aging_stops;

/** Number of engines of each vehicle type in original engine data */
const uint8 _engine_counts[4] = {
	lengthof(_orig_rail_vehicle_info),
	lengthof(_orig_road_vehicle_info),
	lengthof(_orig_ship_vehicle_info),
	lengthof(_orig_aircraft_vehicle_info),
};

/** Offset of the first engine of each vehicle type in original engine data */
const uint8 _engine_offsets[4] = {
	0,
	lengthof(_orig_rail_vehicle_info),
	lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_info),
	lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_info) + lengthof(_orig_ship_vehicle_info),
};

const uint EngineOverrideManager::NUM_DEFAULT_ENGINES = _engine_counts[VEH_TRAIN] + _engine_counts[VEH_ROAD] + _engine_counts[VEH_SHIP] + _engine_counts[VEH_AIRCRAFT];

Engine::Engine() :
	name(NULL),
	overrides_count(0),
	overrides(NULL)
{
}

Engine::Engine(VehicleType type, EngineID base)
{
	this->type = type;
	this->internal_id = base;
	this->list_position = base;

	/* Check if this base engine is within the original engine data range */
	if (base >= _engine_counts[type]) {
		/* Mark engine as valid anyway */
		this->info.climates = 0x80;
		/* Set model life to maximum to make wagons available */
		this->info.base_life = 0xFF;
		return;
	}

	/* Copy the original engine info for this slot */
	this->info = _orig_engine_info[_engine_offsets[type] + base];

	/* Copy the original engine data for this slot */
	switch (type) {
		default: NOT_REACHED();

		case VEH_TRAIN:
			this->u.rail = _orig_rail_vehicle_info[base];
			this->original_image_index = this->u.rail.image_index;
			this->info.string_id = STR_VEHICLE_NAME_TRAIN_ENGINE_RAIL_KIRBY_PAUL_TANK_STEAM + base;

			/* Set the default model life of original wagons to "infinite" */
			if (this->u.rail.railveh_type == RAILVEH_WAGON) this->info.base_life = 0xFF;

			break;

		case VEH_ROAD:
			this->u.road = _orig_road_vehicle_info[base];
			this->original_image_index = this->u.road.image_index;
			this->info.string_id = STR_VEHICLE_NAME_ROAD_MPS_REGAL_BUS + base;
			break;

		case VEH_SHIP:
			this->u.ship = _orig_ship_vehicle_info[base];
			this->original_image_index = this->u.ship.image_index;
			this->info.string_id = STR_VEHICLE_NAME_SHIP_MPS_OIL_TANKER + base;
			break;

		case VEH_AIRCRAFT:
			this->u.air = _orig_aircraft_vehicle_info[base];
			this->original_image_index = this->u.air.image_index;
			this->info.string_id = STR_VEHICLE_NAME_AIRCRAFT_SAMPSON_U52 + base;
			break;
	}
}

Engine::~Engine()
{
	UnloadWagonOverrides(this);
	free(this->name);
}

/**
 * Determines the default cargo type of an engine.
 *
 * Usually a valid cargo is returned, even though the vehicle has zero capacity, and can therefore not carry anything. But the cargotype is still used
 * for livery selection etc..
 *
 * Vehicles with CT_INVALID as default cargo are usally not available, but it can appear as default cargo of articulated parts.
 *
 * @return The default cargo type.
 * @see CanCarryCargo
 */
CargoID Engine::GetDefaultCargoType() const
{
	switch (this->type) {
		case VEH_TRAIN:
			return this->u.rail.cargo_type;

		case VEH_ROAD:
			return this->u.road.cargo_type;

		case VEH_SHIP:
			return this->u.ship.cargo_type;

		case VEH_AIRCRAFT:
			return FindFirstRefittableCargo(this->index);

		default: NOT_REACHED();
	}
}

/**
 * Determines whether an engine can carry something.
 * A vehicle cannot carry anything if its capacity is zero, or none of the possible cargos is available in the climate.
 * @return true if the vehicle can carry something.
 */
bool Engine::CanCarryCargo() const
{
	/* For engines that can appear in a consist (i.e. rail vehicles and (articulated) road vehicles), a capacity
	 * of zero is a special case, to define the vehicle to not carry anything. The default cargotype is still used
	 * for livery selection etc.
	 * Note: Only the property is tested. A capacity callback returning 0 does not have the same effect.
	 */
	switch (this->type) {
		case VEH_TRAIN:
			if (this->u.rail.capacity == 0) return false;
			break;

		case VEH_ROAD:
			if (this->u.road.capacity == 0) return false;
			break;

		case VEH_SHIP:
		case VEH_AIRCRAFT:
			break;

		default: NOT_REACHED();
	}
	return this->GetDefaultCargoType() != CT_INVALID;
}

/**
 * Determines the default cargo capacity of an engine for display purposes.
 *
 * For planes carrying both passenger and mail this is the passenger capacity.
 * For multiheaded engines this is the capacity of both heads.
 * For articulated engines use GetCapacityOfArticulatedParts
 *
 * @return The default capacity
 * @see GetDefaultCargoType
 */
uint Engine::GetDisplayDefaultCapacity() const
{
	if (!this->CanCarryCargo()) return 0;
	switch (type) {
		case VEH_TRAIN:
			return GetEngineProperty(this->index, 0x14, this->u.rail.capacity) + (this->u.rail.railveh_type == RAILVEH_MULTIHEAD ? this->u.rail.capacity : 0);

		case VEH_ROAD:
			return GetEngineProperty(this->index, 0x0F, this->u.road.capacity);

		case VEH_SHIP:
			return GetEngineProperty(this->index, 0x0D, this->u.ship.capacity);

		case VEH_AIRCRAFT:
			return AircraftDefaultCargoCapacity(this->GetDefaultCargoType(), &this->u.air);

		default: NOT_REACHED();
	}
}

Money Engine::GetRunningCost() const
{
	switch (this->type) {
		case VEH_ROAD:
			return this->u.road.running_cost * GetPriceByIndex(this->u.road.running_cost_class) >> 8;

		case VEH_TRAIN:
			return GetEngineProperty(this->index, 0x0D, this->u.rail.running_cost) * GetPriceByIndex(this->u.rail.running_cost_class) >> 8;

		case VEH_SHIP:
			return GetEngineProperty(this->index, 0x0F, this->u.ship.running_cost) * _price.ship_running >> 8;

		case VEH_AIRCRAFT:
			return GetEngineProperty(this->index, 0x0E, this->u.air.running_cost) * _price.aircraft_running >> 8;

		default: NOT_REACHED();
	}
}

Money Engine::GetCost() const
{
	switch (this->type) {
		case VEH_ROAD:
			return GetEngineProperty(this->index, 0x11, this->u.road.cost_factor) * (_price.roadveh_base >> 3) >> 5;

		case VEH_TRAIN:
			if (this->u.rail.railveh_type == RAILVEH_WAGON) {
				return (GetEngineProperty(this->index, 0x17, this->u.rail.cost_factor) * _price.build_railwagon) >> 8;
			} else {
				return GetEngineProperty(this->index, 0x17, this->u.rail.cost_factor) * (_price.build_railvehicle >> 3) >> 5;
			}
		case VEH_SHIP:
			return GetEngineProperty(this->index, 0x0A, this->u.ship.cost_factor) * (_price.ship_base >> 3) >> 5;

		case VEH_AIRCRAFT:
			return GetEngineProperty(this->index, 0x0B, this->u.air.cost_factor) * (_price.aircraft_base >> 3) >> 5;

		default: NOT_REACHED();
	}
}

/**
 * Returns max speed for display purposes
 * @return max speed in km-ish/h
 */
uint Engine::GetDisplayMaxSpeed() const
{
	switch (this->type) {
		case VEH_TRAIN:
			return GetEngineProperty(this->index, 0x09, this->u.rail.max_speed);

		case VEH_ROAD:
			return this->u.road.max_speed / 2;

		case VEH_SHIP:
			return GetEngineProperty(this->index, 0x0B, this->u.ship.max_speed) / 2;

		case VEH_AIRCRAFT:
			return this->u.air.max_speed;

		default: NOT_REACHED();
	}
}

uint Engine::GetPower() const
{
	/* Currently only trains have 'power' */
	switch (this->type) {
		case VEH_TRAIN:
			return GetEngineProperty(this->index, 0x0B, this->u.rail.power);

		default: NOT_REACHED();
	}
}

/**
 * Returns the weight for display purposes.
 * For dual-headed train-engines this is the weight of both heads
 * @return weight in display units metric tons
 */
uint Engine::GetDisplayWeight() const
{
	/* Currently only trains have 'weight' */
	switch (this->type) {
		case VEH_TRAIN:
			return GetEngineProperty(this->index, 0x16, this->u.rail.weight) << (this->u.rail.railveh_type == RAILVEH_MULTIHEAD ? 1 : 0);

		default: NOT_REACHED();
	}
}

/**
 * Returns the tractive effort for display purposes.
 * For dual-headed train-engines this is the tractive effort of both heads
 * @return tractive effort in display units kN
 */
uint Engine::GetDisplayMaxTractiveEffort() const
{
	/* Currently only trains have 'tractive effort' */
	switch (this->type) {
		case VEH_TRAIN:
			return (10 * this->GetDisplayWeight() * GetEngineProperty(this->index, 0x1F, this->u.rail.tractive_effort)) / 256;

		default: NOT_REACHED();
	}
}

/**
 * Returns the vehicle's life length in days.
 * @return the life length
 */
Date Engine::GetLifeLengthInDays() const
{
	/* Assume leap years; this gives the player a bit more than the given amount of years, but never less. */
	return (this->info.lifelength + _settings_game.vehicle.extend_vehicle_life) * DAYS_IN_LEAP_YEAR;
}

/**
 * Initializes the EngineOverrideManager with the default engines.
 */
void EngineOverrideManager::ResetToDefaultMapping()
{
	this->Clear();
	for (VehicleType type = VEH_TRAIN; type <= VEH_AIRCRAFT; type++) {
		for (uint internal_id = 0; internal_id < _engine_counts[type]; internal_id++) {
			EngineIDMapping *eid = this->Append();
			eid->type            = type;
			eid->grfid           = INVALID_GRFID;
			eid->internal_id     = internal_id;
			eid->substitute_id   = internal_id;
		}
	}
}

/**
 * Looks up an EngineID in the EngineOverrideManager
 * @param type Vehicle type
 * @param grf_local_id The local id in the newgrf
 * @param grfid The GrfID that defines the scope of grf_local_id.
 *              If a newgrf overrides the engines of another newgrf, the "scope grfid" is the ID of the overridden newgrf.
 *              If dynnamic_engines is disabled, all newgrf share the same ID scope identified by INVALID_GRFID.
 * @return The engine ID if present, or INVALID_ENGINE if not.
 */
EngineID EngineOverrideManager::GetID(VehicleType type, uint16 grf_local_id, uint32 grfid)
{
	const EngineIDMapping *end = this->End();
	EngineID index = 0;
	for (const EngineIDMapping *eid = this->Begin(); eid != end; eid++, index++) {
		if (eid->type == type && eid->grfid == grfid && eid->internal_id == grf_local_id) {
			return index;
		}
	}
	return INVALID_ENGINE;
}

/** Sets cached values in Company::num_vehicles and Group::num_vehicles
 */
void SetCachedEngineCounts()
{
	size_t engines = Engine::GetPoolSize();

	/* Set up the engine count for all companies */
	Company *c;
	FOR_ALL_COMPANIES(c) {
		free(c->num_engines);
		c->num_engines = CallocT<EngineID>(engines);
	}

	/* Recalculate */
	Group *g;
	FOR_ALL_GROUPS(g) {
		free(g->num_engines);
		g->num_engines = CallocT<EngineID>(engines);
	}

	const Vehicle *v;
	FOR_ALL_VEHICLES(v) {
		if (!IsEngineCountable(v)) continue;

		assert(v->engine_type < engines);

		Company::Get(v->owner)->num_engines[v->engine_type]++;

		if (v->group_id == DEFAULT_GROUP) continue;

		g = Group::Get(v->group_id);
		assert(v->type == g->vehicle_type);
		assert(v->owner == g->owner);

		g->num_engines[v->engine_type]++;
	}
}

void SetupEngines()
{
	_engine_pool.CleanPool();

	assert(_engine_mngr.Length() >= _engine_mngr.NUM_DEFAULT_ENGINES);
	const EngineIDMapping *end = _engine_mngr.End();
	uint index = 0;
	for (const EngineIDMapping *eid = _engine_mngr.Begin(); eid != end; eid++, index++) {
		const Engine *e = new Engine(eid->type, eid->internal_id);
		assert(e->index == index);
	}
}


void ShowEnginePreviewWindow(EngineID engine);

/* Determine if an engine type is a wagon (and not a loco) */
static bool IsWagon(EngineID index)
{
	const Engine *e = Engine::Get(index);
	return e->type == VEH_TRAIN && e->u.rail.railveh_type == RAILVEH_WAGON;
}

static void CalcEngineReliability(Engine *e)
{
	uint age = e->age;

	/* Check for early retirement */
	if (e->company_avail != 0 && !_settings_game.vehicle.never_expire_vehicles && e->info.base_life != 0xFF) {
		int retire_early = e->info.retire_early;
		uint retire_early_max_age = max(0, e->duration_phase_1 + e->duration_phase_2 - retire_early * 12);
		if (retire_early != 0 && age >= retire_early_max_age) {
			/* Early retirement is enabled and we're past the date... */
			e->company_avail = 0;
			AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
		}
	}

	if (age < e->duration_phase_1) {
		uint start = e->reliability_start;
		e->reliability = age * (e->reliability_max - start) / e->duration_phase_1 + start;
	} else if ((age -= e->duration_phase_1) < e->duration_phase_2 || _settings_game.vehicle.never_expire_vehicles || e->info.base_life == 0xFF) {
		/* We are at the peak of this engines life. It will have max reliability.
		 * This is also true if the engines never expire. They will not go bad over time */
		e->reliability = e->reliability_max;
	} else if ((age -= e->duration_phase_2) < e->duration_phase_3) {
		uint max = e->reliability_max;
		e->reliability = (int)age * (int)(e->reliability_final - max) / e->duration_phase_3 + max;
	} else {
		/* time's up for this engine.
		 * We will now completely retire this design */
		e->company_avail = 0;
		e->reliability = e->reliability_final;
		/* Kick this engine out of the lists */
		AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
	}
	InvalidateWindowClasses(WC_BUILD_VEHICLE); // Update to show the new reliability
	InvalidateWindowClasses(WC_REPLACE_VEHICLE);
}

void SetYearEngineAgingStops()
{
	/* Determine last engine aging year, default to 2050 as previously. */
	_year_engine_aging_stops = 2050;

	const Engine *e;
	FOR_ALL_ENGINES(e) {
		const EngineInfo *ei = &e->info;

		/* Exclude certain engines */
		if (!HasBit(ei->climates, _settings_game.game_creation.landscape)) continue;
		if (e->type == VEH_TRAIN && e->u.rail.railveh_type == RAILVEH_WAGON) continue;

		/* Base year ending date on half the model life */
		YearMonthDay ymd;
		ConvertDateToYMD(ei->base_intro + (ei->lifelength * DAYS_IN_LEAP_YEAR) / 2, &ymd);

		_year_engine_aging_stops = max(_year_engine_aging_stops, ymd.year);
	}
}

void StartupOneEngine(Engine *e, Date aging_date)
{
	const EngineInfo *ei = &e->info;
	uint32 r;

	e->age = 0;
	e->flags = 0;
	e->company_avail = 0;

	/* The magic value of 729 days below comes from the NewGRF spec. If the
	 * base intro date is before 1922 then the random number of days is not
	 * added. */
	r = Random();
	e->intro_date = ei->base_intro <= ConvertYMDToDate(1922, 0, 1) ? ei->base_intro : (Date)GB(r, 0, 9) + ei->base_intro;
	if (e->intro_date <= _date) {
		e->age = (aging_date - e->intro_date) >> 5;
		e->company_avail = (CompanyMask)-1;
		e->flags |= ENGINE_AVAILABLE;
	}

	e->reliability_start = GB(r, 16, 14) + 0x7AE0;
	r = Random();
	e->reliability_max   = GB(r,  0, 14) + 0xBFFF;
	e->reliability_final = GB(r, 16, 14) + 0x3FFF;

	r = Random();
	e->duration_phase_1 = GB(r, 0, 5) + 7;
	e->duration_phase_2 = GB(r, 5, 4) + ei->base_life * 12 - 96;
	e->duration_phase_3 = GB(r, 9, 7) + 120;

	e->reliability_spd_dec = ei->decay_speed << 2;

	CalcEngineReliability(e);

	/* prevent certain engines from ever appearing. */
	if (!HasBit(ei->climates, _settings_game.game_creation.landscape)) {
		e->flags |= ENGINE_AVAILABLE;
		e->company_avail = 0;
	}
}

void StartupEngines()
{
	Engine *e;
	/* Aging of vehicles stops, so account for that when starting late */
	const Date aging_date = min(_date, ConvertYMDToDate(_year_engine_aging_stops, 0, 1));

	FOR_ALL_ENGINES(e) {
		StartupOneEngine(e, aging_date);
	}

	/* Update the bitmasks for the vehicle lists */
	Company *c;
	FOR_ALL_COMPANIES(c) {
		c->avail_railtypes = GetCompanyRailtypes(c->index);
		c->avail_roadtypes = GetCompanyRoadtypes(c->index);
	}
}

static void AcceptEnginePreview(EngineID eid, CompanyID company)
{
	Engine *e = Engine::Get(eid);
	Company *c = Company::Get(company);

	SetBit(e->company_avail, company);
	if (e->type == VEH_TRAIN) {
		const RailVehicleInfo *rvi = RailVehInfo(eid);

		assert(rvi->railtype < RAILTYPE_END);
		SetBit(c->avail_railtypes, rvi->railtype);
	} else if (e->type == VEH_ROAD) {
		SetBit(c->avail_roadtypes, HasBit(EngInfo(eid)->misc_flags, EF_ROAD_TRAM) ? ROADTYPE_TRAM : ROADTYPE_ROAD);
	}

	e->preview_company_rank = 0xFF;
	if (company == _local_company) {
		AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);
	}
}

static CompanyID GetBestCompany(uint8 pp)
{
	const Company *c;
	int32 best_hist;
	CompanyID best_company;
	CompanyMask mask = 0;

	do {
		best_hist = -1;
		best_company = INVALID_COMPANY;
		FOR_ALL_COMPANIES(c) {
			if (c->block_preview == 0 && !HasBit(mask, c->index) &&
					c->old_economy[0].performance_history > best_hist) {
				best_hist = c->old_economy[0].performance_history;
				best_company = c->index;
			}
		}

		if (best_company == INVALID_COMPANY) return INVALID_COMPANY;

		SetBit(mask, best_company);
	} while (--pp != 0);

	return best_company;
}

void EnginesDailyLoop()
{
	if (_cur_year >= _year_engine_aging_stops) return;

	Engine *e;
	FOR_ALL_ENGINES(e) {
		EngineID i = e->index;
		if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) {
			if (e->flags & ENGINE_OFFER_WINDOW_OPEN) {
				if (e->preview_company_rank != 0xFF && !--e->preview_wait) {
					e->flags &= ~ENGINE_OFFER_WINDOW_OPEN;
					DeleteWindowById(WC_ENGINE_PREVIEW, i);
					e->preview_company_rank++;
				}
			} else if (e->preview_company_rank != 0xFF) {
				CompanyID best_company = GetBestCompany(e->preview_company_rank);

				if (best_company == INVALID_COMPANY) {
					e->preview_company_rank = 0xFF;
					continue;
				}

				e->flags |= ENGINE_OFFER_WINDOW_OPEN;
				e->preview_wait = 20;
				AI::NewEvent(best_company, new AIEventEnginePreview(i));
				if (IsInteractiveCompany(best_company)) ShowEnginePreviewWindow(i);
			}
		}
	}
}

/** Accept an engine prototype. XXX - it is possible that the top-company
 * changes while you are waiting to accept the offer? Then it becomes invalid
 * @param tile unused
 * @param flags operation to perfom
 * @param p1 engine-prototype offered
 * @param p2 unused
 */
CommandCost CmdWantEnginePreview(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
	Engine *e = Engine::GetIfValid(p1);
	if (e == NULL || GetBestCompany(e->preview_company_rank) != _current_company) return CMD_ERROR;

	if (flags & DC_EXEC) AcceptEnginePreview(p1, _current_company);

	return CommandCost();
}

StringID GetEngineCategoryName(EngineID engine);

static void NewVehicleAvailable(Engine *e)
{
	Vehicle *v;
	Company *c;
	EngineID index = e->index;

	/* In case the company didn't build the vehicle during the intro period,
	 * prevent that company from getting future intro periods for a while. */
	if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) {
		FOR_ALL_COMPANIES(c) {
			uint block_preview = c->block_preview;

			if (!HasBit(e->company_avail, c->index)) continue;

			/* We assume the user did NOT build it.. prove me wrong ;) */
			c->block_preview = 20;

			FOR_ALL_VEHICLES(v) {
				if (v->type == VEH_TRAIN || v->type == VEH_ROAD || v->type == VEH_SHIP ||
						(v->type == VEH_AIRCRAFT && IsNormalAircraft(v))) {
					if (v->owner == c->index && v->engine_type == index) {
						/* The user did prove me wrong, so restore old value */
						c->block_preview = block_preview;
						break;
					}
				}
			}
		}
	}

	e->flags = (e->flags & ~ENGINE_EXCLUSIVE_PREVIEW) | ENGINE_AVAILABLE;
	AddRemoveEngineFromAutoreplaceAndBuildWindows(e->type);

	/* Now available for all companies */
	e->company_avail = (CompanyMask)-1;

	/* Do not introduce new rail wagons */
	if (IsWagon(index)) return;

	if (e->type == VEH_TRAIN) {
		/* maybe make another rail type available */
		RailType railtype = e->u.rail.railtype;
		assert(railtype < RAILTYPE_END);
		FOR_ALL_COMPANIES(c) SetBit(c->avail_railtypes, railtype);
	} else if (e->type == VEH_ROAD) {
		/* maybe make another road type available */
		FOR_ALL_COMPANIES(c) SetBit(c->avail_roadtypes, HasBit(e->info.misc_flags, EF_ROAD_TRAM) ? ROADTYPE_TRAM : ROADTYPE_ROAD);
	}

	AI::BroadcastNewEvent(new AIEventEngineAvailable(index));

	SetDParam(0, GetEngineCategoryName(index));
	SetDParam(1, index);
	AddNewsItem(STR_NEW_VEHICLE_NOW_AVAILABLE_WITH_TYPE, NS_NEW_VEHICLES, NR_ENGINE, index);
}

void EnginesMonthlyLoop()
{
	if (_cur_year < _year_engine_aging_stops) {
		Engine *e;
		FOR_ALL_ENGINES(e) {
			/* Age the vehicle */
			if ((e->flags & ENGINE_AVAILABLE) && e->age != 0xFFFF) {
				e->age++;
				CalcEngineReliability(e);
			}

			if (!(e->flags & ENGINE_AVAILABLE) && _date >= (e->intro_date + DAYS_IN_YEAR)) {
				/* Introduce it to all companies */
				NewVehicleAvailable(e);
			} else if (!(e->flags & (ENGINE_AVAILABLE | ENGINE_EXCLUSIVE_PREVIEW)) && _date >= e->intro_date) {
				/* Introduction date has passed.. show introducing dialog to one companies. */
				e->flags |= ENGINE_EXCLUSIVE_PREVIEW;

				/* Do not introduce new rail wagons */
				if (!IsWagon(e->index))
					e->preview_company_rank = 1; // Give to the company with the highest rating.
			}
		}
	}
}

static bool IsUniqueEngineName(const char *name)
{
	const Engine *e;

	FOR_ALL_ENGINES(e) {
		if (e->name != NULL && strcmp(e->name, name) == 0) return false;
	}

	return true;
}

/** Rename an engine.
 * @param tile unused
 * @param flags operation to perfom
 * @param p1 engine ID to rename
 * @param p2 unused
 */
CommandCost CmdRenameEngine(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
	Engine *e = Engine::GetIfValid(p1);
	if (e == NULL) return CMD_ERROR;

	bool reset = StrEmpty(text);

	if (!reset) {
		if (strlen(text) >= MAX_LENGTH_ENGINE_NAME_BYTES) return CMD_ERROR;
		if (!IsUniqueEngineName(text)) return_cmd_error(STR_NAME_MUST_BE_UNIQUE);
	}

	if (flags & DC_EXEC) {
		free(e->name);

		if (reset) {
			e->name = NULL;
		} else {
			e->name = strdup(text);
		}

		MarkWholeScreenDirty();
	}

	return CommandCost();
}


/** Check if an engine is buildable.
 * @param engine  index of the engine to check.
 * @param type    the type the engine should be.
 * @param company index of the company.
 * @return True if an engine is valid, of the specified type, and buildable by
 *              the given company.
 */
bool IsEngineBuildable(EngineID engine, VehicleType type, CompanyID company)
{
	const Engine *e = Engine::GetIfValid(engine);

	/* check if it's an engine that is in the engine array */
	if (e == NULL) return false;

	/* check if it's an engine of specified type */
	if (e->type != type) return false;

	/* check if it's available */
	if (!HasBit(e->company_avail, company)) return false;

	if (type == VEH_TRAIN) {
		/* Check if the rail type is available to this company */
		const Company *c = Company::Get(company);
		if (!HasBit(c->avail_railtypes, RailVehInfo(engine)->railtype)) return false;
	}

	return true;
}

/**
 * Check if an engine is refittable.
 * Note: Likely you want to use IsArticulatedVehicleRefittable().
 * @param engine index of the engine to check.
 * @return true if the engine is refittable.
 */
bool IsEngineRefittable(EngineID engine)
{
	const Engine *e = Engine::GetIfValid(engine);

	/* check if it's an engine that is in the engine array */
	if (e == NULL) return false;

	if (e->type == VEH_SHIP && !e->u.ship.refittable) return false;

	if (!e->CanCarryCargo()) return false;

	const EngineInfo *ei = &e->info;
	if (ei->refit_mask == 0) return false;

	/* Are there suffixes?
	 * Note: This does not mean the suffixes are actually available for every consist at any time. */
	if (HasBit(ei->callbackmask, CBM_VEHICLE_CARGO_SUFFIX)) return true;

	/* Is there any cargo except the default cargo? */
	CargoID default_cargo = e->GetDefaultCargoType();
	return default_cargo != CT_INVALID && ei->refit_mask != 1U << default_cargo;
}