Function CmdMoveRailVehicle

src/train_cmd.cpp:1221–1405

* Move a rail vehicle around inside the depot. * @param flags type of operation * Note: DoCommandFlag::AutoReplace is set when autoreplace tries to undo its modifications or moves vehicles to temporary locations inside the depot. * @param src_veh source vehicle index * @param dest_veh what wagon to put the source wagon AFTER, XXX - VehicleID::Invalid() to make a new line * @param

 * @return the cost of this operation or an error
 */
CommandCost CmdMoveRailVehicle(DoCommandFlags flags, VehicleID src_veh, VehicleID dest_veh, bool move_chain)
{
	Train *src = Train::GetIfValid(src_veh);
	if (src == nullptr) return CMD_ERROR;

	CommandCost ret = CheckOwnership(src->owner);
	if (ret.Failed()) return ret;

	/* Do not allow moving crashed vehicles inside the depot, it is likely to cause asserts later */
	if (src->vehstatus.Test(VehState::Crashed)) return CMD_ERROR;

	/* if nothing is selected as destination, try and find a matching vehicle to drag to. */
	Train *dst;
	if (dest_veh == VehicleID::Invalid()) {
		dst = (src->IsEngine() || flags.Test(DoCommandFlag::AutoReplace)) ? nullptr : FindGoodVehiclePos(src);
	} else {
		dst = Train::GetIfValid(dest_veh);
		if (dst == nullptr) return CMD_ERROR;

		ret = CheckOwnership(dst->owner);
		if (ret.Failed()) return ret;

		/* Do not allow appending to crashed vehicles, too */
		if (dst->vehstatus.Test(VehState::Crashed)) return CMD_ERROR;
	}

	/* if an articulated part is being handled, deal with its parent vehicle */
	src = src->GetFirstEnginePart();
	if (dst != nullptr) {
		dst = dst->GetFirstEnginePart();
	}

	/* don't move the same vehicle.. */
	if (src == dst) return CommandCost();

	/* locate the head of the two chains */
	Train *src_head = src->First();
	Train *dst_head;
	if (dst != nullptr) {
		dst_head = dst->First();
		if (dst_head->tile != src_head->tile) return CMD_ERROR;
		/* Now deal with articulated part of destination wagon */
		dst = dst->GetLastEnginePart();
	} else {
		dst_head = nullptr;
	}

	if (src->IsRearDualheaded()) return CommandCost(STR_ERROR_REAR_ENGINE_FOLLOW_FRONT);

	/* When moving all wagons, we can't have the same src_head and dst_head */
	if (move_chain && src_head == dst_head) return CommandCost();

	/* When moving a multiheaded part to be place after itself, bail out. */
	if (!move_chain && dst != nullptr && dst->IsRearDualheaded() && src == dst->other_multiheaded_part) return CommandCost();

	/* Check if all vehicles in the source train are stopped inside a depot. */
	if (!src_head->IsStoppedInDepot()) return CommandCost(STR_ERROR_TRAINS_CAN_ONLY_BE_ALTERED_INSIDE_A_DEPOT);