Function CmdLevelLand

src/terraform_cmd.cpp:315–387

* Levels a selected (rectangle) area of land * @param flags for this command type * @param tile end tile of area-drag * @param start_tile start tile of area drag * @param diagonal Whether to use the Orthogonal (false) or Diagonal (true) iterator. * @param LevelMode Mode of leveling \c LevelMode. * @return the cost of this operation or an error */

 * @return the cost of this operation or an error
 */
std::tuple<CommandCost, Money, TileIndex> CmdLevelLand(DoCommandFlags flags, TileIndex tile, TileIndex start_tile, bool diagonal, LevelMode lm)
{
	if (start_tile >= Map::Size()) return { CMD_ERROR, 0, INVALID_TILE };

	/* remember level height */
	uint oldh = TileHeight(start_tile);

	/* compute new height */
	uint h = oldh;
	switch (lm) {
		case LM_LEVEL: break;
		case LM_RAISE: h++; break;
		case LM_LOWER: h--; break;
		default: return { CMD_ERROR, 0, INVALID_TILE };
	}

	/* Check range of destination height */
	if (h > _settings_game.construction.map_height_limit) return { CommandCost(oldh == 0 ? STR_ERROR_ALREADY_AT_SEA_LEVEL : STR_ERROR_TOO_HIGH), 0, INVALID_TILE };

	Money money = GetAvailableMoneyForCommand();
	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost last_error(lm == LM_LEVEL ? STR_ERROR_ALREADY_LEVELLED : INVALID_STRING_ID);
	bool had_success = false;

	const Company *c = Company::GetIfValid(_current_company);
	int limit = (c == nullptr ? INT32_MAX : GB(c->terraform_limit, 16, 16));
	if (limit == 0) return { CommandCost(STR_ERROR_TERRAFORM_LIMIT_REACHED), 0, INVALID_TILE };

	TileIndex error_tile = INVALID_TILE;
	std::unique_ptr<TileIterator> iter = TileIterator::Create(tile, start_tile, diagonal);
	for (; *iter != INVALID_TILE; ++(*iter)) {
		TileIndex t = *iter;
		uint curh = TileHeight(t);
		while (curh != h) {
			CommandCost ret;
			std::tie(ret, std::ignore, error_tile) = Command<CMD_TERRAFORM_LAND>::Do(DoCommandFlags{flags}.Reset(DoCommandFlag::Execute), t, SLOPE_N, curh <= h);
			if (ret.Failed()) {
				last_error = std::move(ret);

				/* Did we reach the limit? */
				if (last_error.GetErrorMessage() == STR_ERROR_TERRAFORM_LIMIT_REACHED) limit = 0;
				break;
			}

			if (flags.Test(DoCommandFlag::Execute)) {
				money -= ret.GetCost();
				if (money < 0) {
					return { cost, ret.GetCost(), error_tile };
				}
				Command<CMD_TERRAFORM_LAND>::Do(flags, t, SLOPE_N, curh <= h);
			} else {
				/* When we're at the terraform limit we better bail (unneeded) testing as well.
				 * This will probably cause the terraforming cost to be underestimated, but only
				 * when it's near the terraforming limit. Even then, the estimation is
				 * completely off due to it basically counting terraforming double, so it being
				 * cut off earlier might even give a better estimate in some cases. */
				if (--limit <= 0) {
					had_success = true;