Function ChangeIndustryProduction

src/industry_cmd.cpp:2872–3077

* Change industry production or do closure * @param i Industry for which changes are performed * @param monthly true if it's the monthly call, false if it's the random call */

 * @param monthly true if it's the monthly call, false if it's the random call
 */
static void ChangeIndustryProduction(Industry *i, bool monthly)
{
	StringID str = STR_NULL;
	bool closeit = false;
	const IndustrySpec *indspec = GetIndustrySpec(i->type);
	bool standard = false;
	bool suppress_message = false;
	bool recalculate_multipliers = false; ///< reinitialize production_rate to match prod_level
	/* use original economy for industries using production related callbacks */
	bool original_economy = indspec->UsesOriginalEconomy();
	uint8_t div = 0;
	uint8_t mul = 0;
	int8_t increment = 0;

	bool callback_enabled = indspec->callback_mask.Test(monthly ? IndustryCallbackMask::MonthlyProdChange : IndustryCallbackMask::ProductionChange);
	if (callback_enabled) {
		std::array<int32_t, 1> regs100;
		uint16_t res = GetIndustryCallback(monthly ? CBID_INDUSTRY_MONTHLYPROD_CHANGE : CBID_INDUSTRY_PRODUCTION_CHANGE, 0, Random(), i, i->type, i->location.tile, regs100);
		if (res != CALLBACK_FAILED) { // failed callback means "do nothing"
			suppress_message = HasBit(res, 7);
			/* Get the custom message if any */
			if (HasBit(res, 8)) str = MapGRFStringID(indspec->grf_prop.grfid, GRFStringID(GB(regs100[0], 0, 16)));
			res = GB(res, 0, 4);
			switch (res) {
				default: NOT_REACHED();
				case 0x0: break;                  // Do nothing, but show the custom message if any
				case 0x1: div = 1; break;         // Halve industry production. If production reaches the quarter of the default, the industry is closed instead.
				case 0x2: mul = 1; break;         // Double industry production if it hasn't reached eight times of the original yet.
				case 0x3: closeit = true; break;  // The industry announces imminent closure, and is physically removed from the map next month.
				case 0x4: standard = true; break; // Do the standard random production change as if this industry was a primary one.
				case 0x5: case 0x6: case 0x7:     // Divide production by 4, 8, 16
				case 0x8: div = res - 0x3; break; // Divide production by 32
				case 0x9: case 0xA: case 0xB:     // Multiply production by 4, 8, 16
				case 0xC: mul = res - 0x7; break; // Multiply production by 32
				case 0xD:                         // decrement production
				case 0xE:                         // increment production
					increment = res == 0x0D ? -1 : 1;
					break;
				case 0xF:                         // Set production to third byte of register 0x100
					i->prod_level = Clamp(GB(regs100[0], 16, 8), PRODLEVEL_MINIMUM, PRODLEVEL_MAXIMUM);
					recalculate_multipliers = true;
					break;
			}
		}
	} else {
		if (monthly == original_economy) return;
		if (!original_economy && _settings_game.economy.type == ET_FROZEN) return;
		if (indspec->life_type == INDUSTRYLIFE_BLACK_HOLE) return;
	}

	if (standard || (!callback_enabled && indspec->life_type.Any({IndustryLifeType::Organic, IndustryLifeType::Extractive}))) {
		/* decrease or increase */
		bool only_decrease = indspec->behaviour.Test(IndustryBehaviour::DontIncrProd) && _settings_game.game_creation.landscape == LandscapeType::Temperate;

		if (original_economy) {
			if (only_decrease || Chance16(1, 3)) {
				/* If more than 60% transported, 66% chance of increase, else 33% chance of increase */
				if (!only_decrease && (i->GetProduced(0).history[LAST_MONTH].PctTransported() > PERCENT_TRANSPORTED_60) != Chance16(1, 3)) {