Function FindSubsidyIndustryCargoRoute

src/subsidy.cpp:323–361

* Tries to create a cargo subsidy with an industry as source. * @return True iff the subsidy was created. */

 * @return True iff the subsidy was created.
 */
bool FindSubsidyIndustryCargoRoute()
{
	if (!Subsidy::CanAllocateItem()) return false;

	/* Select a random industry. */
	const Industry *src_ind = Industry::GetRandom();
	if (src_ind == nullptr) return false;

	uint trans, total;

	CargoType cargo_type;

	/* Randomize cargo type */
	int num_cargos = std::ranges::count_if(src_ind->produced, [](const auto &p) { return IsValidCargoType(p.cargo); });
	if (num_cargos == 0) return false; // industry produces nothing
	int cargo_num = RandomRange(num_cargos) + 1;

	auto it = std::begin(src_ind->produced);
	for (/* nothing */; it != std::end(src_ind->produced); ++it) {
		if (IsValidCargoType(it->cargo)) cargo_num--;
		if (cargo_num == 0) break;
	}
	assert(it != std::end(src_ind->produced)); // indicates loop didn't end as intended

	cargo_type = it->cargo;
	trans = it->history[LAST_MONTH].PctTransported();
	total = it->history[LAST_MONTH].production;

	/* Quit if no production in this industry
	 * or if the pct transported is already large enough
	 * or if the cargo is automatically distributed */
	if (total == 0 || trans > SUBSIDY_MAX_PCT_TRANSPORTED ||
			!IsValidCargoType(cargo_type) ||
			_settings_game.linkgraph.GetDistributionType(cargo_type) != DT_MANUAL) {
		return false;
	}

	return FindSubsidyCargoDestination(cargo_type, {src_ind->index, SourceType::Industry});
}

/**
 * Tries to find a suitable destination for the given source and cargo.