Function FindSubsidyCargoDestination

src/subsidy.cpp:369–422

* Tries to find a suitable destination for the given source and cargo. * @param cargo_type Subsidized cargo. * @param src Source of cargo. * @return True iff the subsidy was created. */

 * @return True iff the subsidy was created.
 */
bool FindSubsidyCargoDestination(CargoType cargo_type, Source src)
{
	/* Choose a random destination. */
	Source dst{Source::Invalid, Chance16(1, 2) ? SourceType::Town : SourceType::Industry};

	switch (dst.type) {
		case SourceType::Town: {
			/* Select a random town. */
			const Town *dst_town = Town::GetRandom();

			/* Calculate cargo acceptance of houses around town center. */
			CargoArray town_cargo_accepted{};
			TileArea ta = TileArea(dst_town->xy, 1, 1).Expand(SUBSIDY_TOWN_CARGO_RADIUS);
			for (TileIndex tile : ta) {
				if (IsTileType(tile, MP_HOUSE)) {
					AddAcceptedCargo(tile, town_cargo_accepted, nullptr);
				}
			}

			/* Check if the town can accept this cargo. */
			if (town_cargo_accepted[cargo_type] < 8) return false;

			dst.SetIndex(dst_town->index);
			break;
		}

		case SourceType::Industry: {
			/* Select a random industry. */
			const Industry *dst_ind = Industry::GetRandom();
			if (dst_ind == nullptr) return false;

			/* The industry must accept the cargo */
			if (!dst_ind->IsCargoAccepted(cargo_type)) return false;

			dst.SetIndex(dst_ind->index);
			break;
		}

		default: NOT_REACHED();
	}

	/* Check that the source and the destination are not the same. */
	if (src == dst) return false;

	/* Check distance between source and destination. */
	if (!CheckSubsidyDistance(src, dst)) return false;

	/* Avoid duplicate subsidies. */
	if (CheckSubsidyDuplicate(cargo_type, src, dst)) return false;

	CreateSubsidy(cargo_type, src, dst);

	return true;
}

/** Perform the economy monthly update of open subsidies, and try to create a new one. */
static const IntervalTimer<TimerGameEconomy> _economy_subsidies_monthly({TimerGameEconomy::MONTH, TimerGameEconomy::Priority::SUBSIDY}, [](auto)