src/subsidy.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   6  */
   7
   8 /** @file subsidy.cpp Handling of subsidies. */
   9
  10 #include "stdafx.h"
  11 #include "company_func.h"
  12 #include "industry.h"
  13 #include "town.h"
  14 #include "news_func.h"
  15 #include "ai/ai.hpp"
  16 #include "station_base.h"
  17 #include "strings_func.h"
  18 #include "window_func.h"
  19 #include "subsidy_base.h"
  20 #include "subsidy_func.h"
  21 #include "core/pool_func.hpp"
  22 #include "core/random_func.hpp"
  23 #include "core/container_func.hpp"
  24 #include "game/game.hpp"
  25 #include "command_func.h"
  26 #include "string_func.h"
  27 #include "tile_cmd.h"
  28 #include "subsidy_cmd.h"
  29 #include "timer/timer.h"
  30 #include "timer/timer_game_economy.h"
  31
  32 #include "table/strings.h"
  33
  34 #include "safeguards.h"
  35
  36 SubsidyPool _subsidy_pool("Subsidy"); ///< Pool for the subsidies.
  37 INSTANTIATE_POOL_METHODS(Subsidy)
  38
  39 /**
  40  * Marks subsidy as awarded, creates news and AI event
  41  * @param company awarded company
  42  */
  43 void Subsidy::AwardTo(CompanyID company)
  44 {
  45         assert(!this->IsAwarded());
  46
  47         this->awarded = company;
  48         this->remaining = _settings_game.difficulty.subsidy_duration * CalendarTime::MONTHS_IN_YEAR;
  49
  50         SetDParam(0, company);
  51         std::string company_name = GetString(STR_COMPANY_NAME);
  52
  53         /* Add a news item */
  54         std::pair<NewsReferenceType, NewsReferenceType> reftype = SetupSubsidyDecodeParam(this, SubsidyDecodeParamType::NewsAwarded, 1);
  55
  56         SetDParamStr(0, company_name);
  57         AddNewsItem(
  58                 STR_NEWS_SERVICE_SUBSIDY_AWARDED_HALF + _settings_game.difficulty.subsidy_multiplier,
  59                 NT_SUBSIDIES, NF_NORMAL,
  60                 reftype.first, this->src, reftype.second, this->dst
  61         );
  62         AI::BroadcastNewEvent(new ScriptEventSubsidyAwarded(this->index));
  63         Game::NewEvent(new ScriptEventSubsidyAwarded(this->index));
  64
  65         InvalidateWindowData(WC_SUBSIDIES_LIST, 0);
  66 }
  67
  68 /**
  69  * Setup the string parameters for printing the subsidy at the screen, and compute the news reference for the subsidy.
  70  * @param s %Subsidy being printed.
  71  * @param mode Type of subsidy news message to decide on parameter format.
  72  * @param parameter_offset The location/index in the String DParams to start decoding the subsidy's parameters. Defaults to 0.
  73  * @return Reference of the subsidy in the news system.
  74  */
  75 std::pair<NewsReferenceType, NewsReferenceType> SetupSubsidyDecodeParam(const Subsidy *s, SubsidyDecodeParamType mode, uint parameter_offset)
  76 {
  77         NewsReferenceType reftype1 = NR_NONE;
  78         NewsReferenceType reftype2 = NR_NONE;
  79
  80         /* Always use the plural form of the cargo name - trying to decide between plural or singular causes issues for translations */
  81         const CargoSpec *cs = CargoSpec::Get(s->cargo_type);
  82         SetDParam(parameter_offset, cs->name);
  83
  84         switch (s->src_type) {
  85                 case SourceType::Industry:
  86                         reftype1 = NR_INDUSTRY;
  87                         SetDParam(parameter_offset + 1, STR_INDUSTRY_NAME);
  88                         break;
  89                 case SourceType::Town:
  90                         reftype1 = NR_TOWN;
  91                         SetDParam(parameter_offset + 1, STR_TOWN_NAME);
  92                         break;
  93                 default: NOT_REACHED();
  94         }
  95         SetDParam(parameter_offset + 2, s->src);
  96
  97         switch (s->dst_type) {
  98                 case SourceType::Industry:
  99                         reftype2 = NR_INDUSTRY;
 100                         SetDParam(parameter_offset + 4, STR_INDUSTRY_NAME);
 101                         break;
 102                 case SourceType::Town:
 103                         reftype2 = NR_TOWN;
 104                         SetDParam(parameter_offset + 4, STR_TOWN_NAME);
 105                         break;
 106                 default: NOT_REACHED();
 107         }
 108         SetDParam(parameter_offset + 5, s->dst);
 109
 110         /* If the subsidy is being offered or awarded, the news item mentions the subsidy duration. */
 111         if (mode == SubsidyDecodeParamType::NewsOffered || mode == SubsidyDecodeParamType::NewsAwarded) {
 112                 SetDParam(parameter_offset + 7, _settings_game.difficulty.subsidy_duration);
 113         }
 114
 115         return std::pair<NewsReferenceType, NewsReferenceType>(reftype1, reftype2);
 116 }
 117
 118 /**
 119  * Sets a flag indicating that given town/industry is part of subsidised route.
 120  * @param type is it a town or an industry?
 121  * @param index index of town/industry
 122  * @param flag flag to set
 123  */
 124 static inline void SetPartOfSubsidyFlag(SourceType type, SourceID index, PartOfSubsidy flag)
 125 {
 126         switch (type) {
 127                 case SourceType::Industry: Industry::Get(index)->part_of_subsidy |= flag; return;
 128                 case SourceType::Town:   Town::Get(index)->cache.part_of_subsidy |= flag; return;
 129                 default: NOT_REACHED();
 130         }
 131 }
 132
 133 /** Perform a full rebuild of the subsidies cache. */
 134 void RebuildSubsidisedSourceAndDestinationCache()
 135 {
 136         for (Town *t : Town::Iterate()) t->cache.part_of_subsidy = POS_NONE;
 137
 138         for (Industry *i : Industry::Iterate()) i->part_of_subsidy = POS_NONE;
 139
 140         for (const Subsidy *s : Subsidy::Iterate()) {
 141                 SetPartOfSubsidyFlag(s->src_type, s->src, POS_SRC);
 142                 SetPartOfSubsidyFlag(s->dst_type, s->dst, POS_DST);
 143         }
 144 }
 145
 146 /**
 147  * Delete the subsidies associated with a given cargo source type and id.
 148  * @param type  Cargo source type of the id.
 149  * @param index Id to remove.
 150  */
 151 void DeleteSubsidyWith(SourceType type, SourceID index)
 152 {
 153         bool dirty = false;
 154
 155         for (Subsidy *s : Subsidy::Iterate()) {
 156                 if ((s->src_type == type && s->src == index) || (s->dst_type == type && s->dst == index)) {
 157                         delete s;
 158                         dirty = true;
 159                 }
 160         }
 161
 162         if (dirty) {
 163                 InvalidateWindowData(WC_SUBSIDIES_LIST, 0);
 164                 RebuildSubsidisedSourceAndDestinationCache();
 165         }
 166 }
 167
 168 /**
 169  * Check whether a specific subsidy already exists.
 170  * @param cargo Cargo type.
 171  * @param src_type Type of source of the cargo, affects interpretation of \a src.
 172  * @param src Id of the source.
 173  * @param dst_type Type of the destination of the cargo, affects interpretation of \a dst.
 174  * @param dst Id of the destination.
 175  * @return \c true if the subsidy already exists, \c false if not.
 176  */
 177 static bool CheckSubsidyDuplicate(CargoID cargo, SourceType src_type, SourceID src, SourceType dst_type, SourceID dst)
 178 {
 179         for (const Subsidy *s : Subsidy::Iterate()) {
 180                 if (s->cargo_type == cargo &&
 181                                 s->src_type == src_type && s->src == src &&
 182                                 s->dst_type == dst_type && s->dst == dst) {
 183                         return true;
 184                 }
 185         }
 186         return false;
 187 }
 188
 189 /**
 190  * Checks if the source and destination of a subsidy are inside the distance limit.
 191  * @param src_type Type of \a src.
 192  * @param src      Index of source.
 193  * @param dst_type Type of \a dst.
 194  * @param dst      Index of destination.
 195  * @return True if they are inside the distance limit.
 196  */
 197 static bool CheckSubsidyDistance(SourceType src_type, SourceID src, SourceType dst_type, SourceID dst)
 198 {
 199         TileIndex tile_src = (src_type == SourceType::Town) ? Town::Get(src)->xy : Industry::Get(src)->location.tile;
 200         TileIndex tile_dst = (dst_type == SourceType::Town) ? Town::Get(dst)->xy : Industry::Get(dst)->location.tile;
 201
 202         return (DistanceManhattan(tile_src, tile_dst) <= SUBSIDY_MAX_DISTANCE);
 203 }
 204
 205 /**
 206  * Creates a subsidy with the given parameters.
 207  * @param cid      Subsidised cargo.
 208  * @param src_type Type of \a src.
 209  * @param src      Index of source.
 210  * @param dst_type Type of \a dst.
 211  * @param dst      Index of destination.
 212  */
 213 void CreateSubsidy(CargoID cid, SourceType src_type, SourceID src, SourceType dst_type, SourceID dst)
 214 {
 215         Subsidy *s = new Subsidy();
 216         s->cargo_type = cid;
 217         s->src_type = src_type;
 218         s->src = src;
 219         s->dst_type = dst_type;
 220         s->dst = dst;
 221         s->remaining = SUBSIDY_OFFER_MONTHS;
 222         s->awarded = INVALID_COMPANY;
 223
 224         std::pair<NewsReferenceType, NewsReferenceType> reftype = SetupSubsidyDecodeParam(s, SubsidyDecodeParamType::NewsOffered);
 225         AddNewsItem(STR_NEWS_SERVICE_SUBSIDY_OFFERED, NT_SUBSIDIES, NF_NORMAL, reftype.first, s->src, reftype.second, s->dst);
 226         SetPartOfSubsidyFlag(s->src_type, s->src, POS_SRC);
 227         SetPartOfSubsidyFlag(s->dst_type, s->dst, POS_DST);
 228         AI::BroadcastNewEvent(new ScriptEventSubsidyOffer(s->index));
 229         Game::NewEvent(new ScriptEventSubsidyOffer(s->index));
 230
 231         InvalidateWindowData(WC_SUBSIDIES_LIST, 0);
 232 }
 233
 234 /**
 235  * Create a new subsidy.
 236  * @param flags type of operation
 237  * @param cid CargoID of subsidy.
 238  * @param src_type SourceType of source.
 239  * @param src SourceID of source.
 240  * @param dst_type SourceType of destination.
 241  * @param dst SourceID of destination.
 242  * @return the cost of this operation or an error
 243  */
 244 CommandCost CmdCreateSubsidy(DoCommandFlag flags, CargoID cid, SourceType src_type, SourceID src, SourceType dst_type, SourceID dst)
 245 {
 246         if (!Subsidy::CanAllocateItem()) return CMD_ERROR;
 247
 248         if (_current_company != OWNER_DEITY) return CMD_ERROR;
 249
 250         if (cid >= NUM_CARGO || !::CargoSpec::Get(cid)->IsValid()) return CMD_ERROR;
 251
 252         switch (src_type) {
 253                 case SourceType::Town:
 254                         if (!Town::IsValidID(src)) return CMD_ERROR;
 255                         break;
 256                 case SourceType::Industry:
 257                         if (!Industry::IsValidID(src)) return CMD_ERROR;
 258                         break;
 259                 default:
 260                         return CMD_ERROR;
 261         }
 262         switch (dst_type) {
 263                 case SourceType::Town:
 264                         if (!Town::IsValidID(dst)) return CMD_ERROR;
 265                         break;
 266                 case SourceType::Industry:
 267                         if (!Industry::IsValidID(dst)) return CMD_ERROR;
 268                         break;
 269                 default:
 270                         return CMD_ERROR;
 271         }
 272
 273         if (flags & DC_EXEC) {
 274                 CreateSubsidy(cid, src_type, src, dst_type, dst);
 275         }
 276
 277         return CommandCost();
 278 }
 279
 280 /**
 281  * Tries to create a passenger subsidy between two towns.
 282  * @return True iff the subsidy was created.
 283  */
 284 bool FindSubsidyPassengerRoute()
 285 {
 286         if (!Subsidy::CanAllocateItem()) return false;
 287
 288         /* Pick a random TPE_PASSENGER type */
 289         uint32_t r = RandomRange(static_cast<uint>(CargoSpec::town_production_cargoes[TPE_PASSENGERS].size()));
 290         CargoID cid = CargoSpec::town_production_cargoes[TPE_PASSENGERS][r]->Index();
 291
 292         const Town *src = Town::GetRandom();
 293         if (src->cache.population < SUBSIDY_PAX_MIN_POPULATION ||
 294                         src->GetPercentTransported(cid) > SUBSIDY_MAX_PCT_TRANSPORTED) {
 295                 return false;
 296         }
 297
 298         const Town *dst = Town::GetRandom();
 299         if (dst->cache.population < SUBSIDY_PAX_MIN_POPULATION || src == dst) {
 300                 return false;
 301         }
 302
 303         if (DistanceManhattan(src->xy, dst->xy) > SUBSIDY_MAX_DISTANCE) return false;
 304         if (CheckSubsidyDuplicate(cid, SourceType::Town, src->index, SourceType::Town, dst->index)) return false;
 305
 306         CreateSubsidy(cid, SourceType::Town, src->index, SourceType::Town, dst->index);
 307
 308         return true;
 309 }
 310
 311 bool FindSubsidyCargoDestination(CargoID cid, SourceType src_type, SourceID src);
 312
 313
 314 /**
 315  * Tries to create a cargo subsidy with a town as source.
 316  * @return True iff the subsidy was created.
 317  */
 318 bool FindSubsidyTownCargoRoute()
 319 {
 320         if (!Subsidy::CanAllocateItem()) return false;
 321
 322         SourceType src_type = SourceType::Town;
 323
 324         /* Select a random town. */
 325         const Town *src_town = Town::GetRandom();
 326         if (src_town->cache.population < SUBSIDY_CARGO_MIN_POPULATION) return false;
 327
 328         /* Calculate the produced cargo of houses around town center. */
 329         CargoArray town_cargo_produced{};
 330         TileArea ta = TileArea(src_town->xy, 1, 1).Expand(SUBSIDY_TOWN_CARGO_RADIUS);
 331         for (TileIndex tile : ta) {
 332                 if (IsTileType(tile, MP_HOUSE)) {
 333                         AddProducedCargo(tile, town_cargo_produced);
 334                 }
 335         }
 336
 337         /* Passenger subsidies are not handled here. */
 338         for (const CargoSpec *cs : CargoSpec::town_production_cargoes[TPE_PASSENGERS]) {
 339                 town_cargo_produced[cs->Index()] = 0;
 340         }
 341
 342         uint8_t cargo_count = town_cargo_produced.GetCount();
 343
 344         /* No cargo produced at all? */
 345         if (cargo_count == 0) return false;
 346
 347         /* Choose a random cargo that is produced in the town. */
 348         uint8_t cargo_number = RandomRange(cargo_count);
 349         CargoID cid;
 350         for (cid = 0; cid < NUM_CARGO; cid++) {
 351                 if (town_cargo_produced[cid] > 0) {
 352                         if (cargo_number == 0) break;
 353                         cargo_number--;
 354                 }
 355         }
 356
 357         /* Avoid using invalid NewGRF cargoes. */
 358         if (!CargoSpec::Get(cid)->IsValid() ||
 359                         _settings_game.linkgraph.GetDistributionType(cid) != DT_MANUAL) {
 360                 return false;
 361         }
 362
 363         /* Quit if the percentage transported is large enough. */
 364         if (src_town->GetPercentTransported(cid) > SUBSIDY_MAX_PCT_TRANSPORTED) return false;
 365
 366         SourceID src = src_town->index;
 367
 368         return FindSubsidyCargoDestination(cid, src_type, src);
 369 }
 370
 371 /**
 372  * Tries to create a cargo subsidy with an industry as source.
 373  * @return True iff the subsidy was created.
 374  */
 375 bool FindSubsidyIndustryCargoRoute()
 376 {
 377         if (!Subsidy::CanAllocateItem()) return false;
 378
 379         SourceType src_type = SourceType::Industry;
 380
 381         /* Select a random industry. */
 382         const Industry *src_ind = Industry::GetRandom();
 383         if (src_ind == nullptr) return false;
 384
 385         uint trans, total;
 386
 387         CargoID cid;
 388
 389         /* Randomize cargo type */
 390         int num_cargos = std::count_if(std::begin(src_ind->produced), std::end(src_ind->produced), [](const auto &p) { return IsValidCargoID(p.cargo); });
 391         if (num_cargos == 0) return false; // industry produces nothing
 392         int cargo_num = RandomRange(num_cargos) + 1;
 393
 394         auto it = std::begin(src_ind->produced);
 395         for (/* nothing */; it != std::end(src_ind->produced); ++it) {
 396                 if (IsValidCargoID(it->cargo)) cargo_num--;
 397                 if (cargo_num == 0) break;
 398         }
 399         assert(it != std::end(src_ind->produced)); // indicates loop didn't end as intended
 400
 401         cid = it->cargo;
 402         trans = it->history[LAST_MONTH].PctTransported();
 403         total = it->history[LAST_MONTH].production;
 404
 405         /* Quit if no production in this industry
 406          * or if the pct transported is already large enough
 407          * or if the cargo is automatically distributed */
 408         if (total == 0 || trans > SUBSIDY_MAX_PCT_TRANSPORTED ||
 409                         !IsValidCargoID(cid) ||
 410                         _settings_game.linkgraph.GetDistributionType(cid) != DT_MANUAL) {
 411                 return false;
 412         }
 413
 414         SourceID src = src_ind->index;
 415
 416         return FindSubsidyCargoDestination(cid, src_type, src);
 417 }
 418
 419 /**
 420  * Tries to find a suitable destination for the given source and cargo.
 421  * @param cid      Subsidized cargo.
 422  * @param src_type Type of \a src.
 423  * @param src      Index of source.
 424  * @return True iff the subsidy was created.
 425  */
 426 bool FindSubsidyCargoDestination(CargoID cid, SourceType src_type, SourceID src)
 427 {
 428         /* Choose a random destination. */
 429         SourceType dst_type = Chance16(1, 2) ? SourceType::Town : SourceType::Industry;
 430
 431         SourceID dst;
 432         switch (dst_type) {
 433                 case SourceType::Town: {
 434                         /* Select a random town. */
 435                         const Town *dst_town = Town::GetRandom();
 436
 437                         /* Calculate cargo acceptance of houses around town center. */
 438                         CargoArray town_cargo_accepted{};
 439                         TileArea ta = TileArea(dst_town->xy, 1, 1).Expand(SUBSIDY_TOWN_CARGO_RADIUS);
 440                         for (TileIndex tile : ta) {
 441                                 if (IsTileType(tile, MP_HOUSE)) {
 442                                         AddAcceptedCargo(tile, town_cargo_accepted, nullptr);
 443                                 }
 444                         }
 445
 446                         /* Check if the town can accept this cargo. */
 447                         if (town_cargo_accepted[cid] < 8) return false;
 448
 449                         dst = dst_town->index;
 450                         break;
 451                 }
 452
 453                 case SourceType::Industry: {
 454                         /* Select a random industry. */
 455                         const Industry *dst_ind = Industry::GetRandom();
 456                         if (dst_ind == nullptr) return false;
 457
 458                         /* The industry must accept the cargo */
 459                         if (!dst_ind->IsCargoAccepted(cid)) return false;
 460
 461                         dst = dst_ind->index;
 462                         break;
 463                 }
 464
 465                 default: NOT_REACHED();
 466         }
 467
 468         /* Check that the source and the destination are not the same. */
 469         if (src_type == dst_type && src == dst) return false;
 470
 471         /* Check distance between source and destination. */
 472         if (!CheckSubsidyDistance(src_type, src, dst_type, dst)) return false;
 473
 474         /* Avoid duplicate subsidies. */
 475         if (CheckSubsidyDuplicate(cid, src_type, src, dst_type, dst)) return false;
 476
 477         CreateSubsidy(cid, src_type, src, dst_type, dst);
 478
 479         return true;
 480 }
 481
 482 /** Perform the economy monthly update of open subsidies, and try to create a new one. */
 483 static IntervalTimer<TimerGameEconomy> _economy_subsidies_monthly({TimerGameEconomy::MONTH, TimerGameEconomy::Priority::SUBSIDY}, [](auto)
 484 {
 485         bool modified = false;
 486
 487         for (Subsidy *s : Subsidy::Iterate()) {
 488                 if (--s->remaining == 0) {
 489                         if (!s->IsAwarded()) {
 490                                 std::pair<NewsReferenceType, NewsReferenceType> reftype = SetupSubsidyDecodeParam(s, SubsidyDecodeParamType::NewsWithdrawn);
 491                                 AddNewsItem(STR_NEWS_OFFER_OF_SUBSIDY_EXPIRED, NT_SUBSIDIES, NF_NORMAL, reftype.first, s->src, reftype.second, s->dst);
 492                                 AI::BroadcastNewEvent(new ScriptEventSubsidyOfferExpired(s->index));
 493                                 Game::NewEvent(new ScriptEventSubsidyOfferExpired(s->index));
 494                         } else {
 495                                 if (s->awarded == _local_company) {
 496                                         std::pair<NewsReferenceType, NewsReferenceType> reftype = SetupSubsidyDecodeParam(s, SubsidyDecodeParamType::NewsWithdrawn);
 497                                         AddNewsItem(STR_NEWS_SUBSIDY_WITHDRAWN_SERVICE, NT_SUBSIDIES, NF_NORMAL, reftype.first, s->src, reftype.second, s->dst);
 498                                 }
 499                                 AI::BroadcastNewEvent(new ScriptEventSubsidyExpired(s->index));
 500                                 Game::NewEvent(new ScriptEventSubsidyExpired(s->index));
 501                         }
 502                         delete s;
 503                         modified = true;
 504                 }
 505         }
 506
 507         if (modified) {
 508                 RebuildSubsidisedSourceAndDestinationCache();
 509         } else if (_settings_game.difficulty.subsidy_duration == 0) {
 510                 /* If subsidy duration is set to 0, subsidies are disabled, so bail out. */
 511                 return;
 512         } else if (_settings_game.linkgraph.distribution_pax != DT_MANUAL &&
 513                            _settings_game.linkgraph.distribution_mail != DT_MANUAL &&
 514                            _settings_game.linkgraph.distribution_armoured != DT_MANUAL &&
 515                            _settings_game.linkgraph.distribution_default != DT_MANUAL) {
 516                 /* Return early if there are no manually distributed cargoes and if we
 517                  * don't need to invalidate the subsidies window. */
 518                 return;
 519         }
 520
 521         bool passenger_subsidy = false;
 522         bool town_subsidy = false;
 523         bool industry_subsidy = false;
 524
 525         int random_chance = RandomRange(16);
 526
 527         if (random_chance < 2 && _settings_game.linkgraph.distribution_pax == DT_MANUAL) {
 528                 /* There is a 1/8 chance each month of generating a passenger subsidy. */
 529                 int n = 1000;
 530
 531                 do {
 532                         passenger_subsidy = FindSubsidyPassengerRoute();
 533                 } while (!passenger_subsidy && n--);
 534         } else if (random_chance == 2) {
 535                 /* Cargo subsidies with a town as a source have a 1/16 chance. */
 536                 int n = 1000;
 537
 538                 do {
 539                         town_subsidy = FindSubsidyTownCargoRoute();
 540                 } while (!town_subsidy && n--);
 541         } else if (random_chance == 3) {
 542                 /* Cargo subsidies with an industry as a source have a 1/16 chance. */
 543                 int n = 1000;
 544
 545                 do {
 546                         industry_subsidy = FindSubsidyIndustryCargoRoute();
 547                 } while (!industry_subsidy && n--);
 548         }
 549
 550         modified |= passenger_subsidy || town_subsidy || industry_subsidy;
 551
 552         if (modified) InvalidateWindowData(WC_SUBSIDIES_LIST, 0);
 553 });
 554
 555 /**
 556  * Tests whether given delivery is subsidised and possibly awards the subsidy to delivering company
 557  * @param cargo_type type of cargo
 558  * @param company company delivering the cargo
 559  * @param src_type type of \a src
 560  * @param src index of source
 561  * @param st station where the cargo is delivered to
 562  * @return is the delivery subsidised?
 563  */
 564 bool CheckSubsidised(CargoID cargo_type, CompanyID company, SourceType src_type, SourceID src, const Station *st)
 565 {
 566         /* If the source isn't subsidised, don't continue */
 567         if (src == INVALID_SOURCE) return false;
 568         switch (src_type) {
 569                 case SourceType::Industry:
 570                         if (!(Industry::Get(src)->part_of_subsidy & POS_SRC)) return false;
 571                         break;
 572                 case SourceType::Town:
 573                         if (!(Town::Get(src)->cache.part_of_subsidy & POS_SRC)) return false;
 574                         break;
 575                 default: return false;
 576         }
 577
 578         /* Remember all towns near this station (at least one house in its catchment radius)
 579          * which are destination of subsidised path. Do that only if needed */
 580         std::vector<const Town *> towns_near;
 581         if (!st->rect.IsEmpty()) {
 582                 for (const Subsidy *s : Subsidy::Iterate()) {
 583                         /* Don't create the cache if there is no applicable subsidy with town as destination */
 584                         if (s->dst_type != SourceType::Town) continue;
 585                         if (s->cargo_type != cargo_type || s->src_type != src_type || s->src != src) continue;
 586                         if (s->IsAwarded() && s->awarded != company) continue;
 587
 588                         BitmapTileIterator it(st->catchment_tiles);
 589                         for (TileIndex tile = it; tile != INVALID_TILE; tile = ++it) {
 590                                 if (!IsTileType(tile, MP_HOUSE)) continue;
 591                                 const Town *t = Town::GetByTile(tile);
 592                                 if (t->cache.part_of_subsidy & POS_DST) include(towns_near, t);
 593                         }
 594                         break;
 595                 }
 596         }
 597
 598         bool subsidised = false;
 599
 600         /* Check if there's a (new) subsidy that applies. There can be more subsidies triggered by this delivery!
 601          * Think about the case that subsidies are A->B and A->C and station has both B and C in its catchment area */
 602         for (Subsidy *s : Subsidy::Iterate()) {
 603                 if (s->cargo_type == cargo_type && s->src_type == src_type && s->src == src && (!s->IsAwarded() || s->awarded == company)) {
 604                         switch (s->dst_type) {
 605                                 case SourceType::Industry:
 606                                         for (const auto &i : st->industries_near) {
 607                                                 if (s->dst == i.industry->index) {
 608                                                         assert(i.industry->part_of_subsidy & POS_DST);
 609                                                         subsidised = true;
 610                                                         if (!s->IsAwarded()) s->AwardTo(company);
 611                                                 }
 612                                         }
 613                                         break;
 614                                 case SourceType::Town:
 615                                         for (const Town *tp : towns_near) {
 616                                                 if (s->dst == tp->index) {
 617                                                         assert(tp->cache.part_of_subsidy & POS_DST);
 618                                                         subsidised = true;
 619                                                         if (!s->IsAwarded()) s->AwardTo(company);
 620                                                 }
 621                                         }
 622                                         break;
 623                                 default:
 624                                         NOT_REACHED();
 625                         }
 626                 }
 627         }
 628
 629         return subsidised;
 630 }