* move the cargo from one engine to another if possible

 */

static void MoveVehicleCargo(Vehicle *dest, Vehicle *source)

{

	Vehicle *v = dest;

	int units_moved;

	do {

		do {

			if (source->cargo_type != dest->cargo_type)

				continue;	// cargo not compatible

			if (dest->cargo_count == dest->cargo_cap)

				continue;	// the destination vehicle is already full

			units_moved = min(source->cargo_count, dest->cargo_cap - dest->cargo_count);

			source->cargo_count -= units_moved;

			dest->cargo_count   += units_moved;

			dest->cargo_source   = source->cargo_source;

			// copy the age of the cargo

			dest->cargo_days   = source->cargo_days;

			dest->day_counter  = source->day_counter;

			dest->tick_counter = source->tick_counter;

		} while (source->cargo_count > 0 && (dest = dest->next) != NULL);

		dest = v;

	} while ((source = source->next) != NULL);

}

/* Replaces a vehicle (used to be called autorenew)

 * This function is only called from MaybeReplaceVehicle()

 * Must be called with _current_player set to the owner of the vehicle

 * @param w Vehicle to replace

 * @param flags is the flags to use when calling DoCommand(). Mainly DC_EXEC counts

 * @return value is cost of the replacement or CMD_ERROR

 */

static int32 ReplaceVehicle(Vehicle **w, byte flags)

{

	int32 cost;

	Vehicle *old_v = *w;

	const Player *p = GetPlayer(old_v->owner);

	EngineID new_engine_type;

	const UnitID cached_unitnumber = old_v->unitnumber;

	bool new_front = false;

	Vehicle *new_v = NULL;

	char vehicle_name[32];

	if (new_engine_type == INVALID_ENGINE) new_engine_type = old_v->engine_type;

	cost = DoCommand(old_v->x_pos, old_v->y_pos, new_engine_type, 1, flags, CMD_BUILD_VEH(old_v->type));

	if (CmdFailed(cost)) return cost;

	if (flags & DC_EXEC) {

		new_v = GetVehicle(_new_vehicle_id);

		*w = new_v;	//we changed the vehicle, so MaybeReplaceVehicle needs to work on the new one. Now we tell it what the new one is

		/* refit if needed */

		if (new_v->type != VEH_Road) { // road vehicles can't be refitted

			if (old_v->cargo_type != new_v->cargo_type && old_v->cargo_cap != 0 && new_v->cargo_cap != 0) {// some train engines do not have cargo capacity

				DoCommand(0, 0, new_v->index, old_v->cargo_type, DC_EXEC, CMD_REFIT_VEH(new_v->type));

			}

		}

		if (old_v->type == VEH_Train && !IsFrontEngine(old_v)) {

			/* this is a railcar. We need to move the car into the train

			 * We add the new engine after the old one instead of replacing it. It will give the same result anyway when we

			 * sell the old engine in a moment

			 */

			DoCommand(0, 0, (GetPrevVehicleInChain(old_v)->index << 16) | new_v->index, 1, DC_EXEC, CMD_MOVE_RAIL_VEHICLE);

			/* Now we move the old one out of the train */

			DoCommand(0, 0, (INVALID_VEHICLE << 16) | old_v->index, 0, DC_EXEC, CMD_MOVE_RAIL_VEHICLE);

		} else {

			// copy/clone the orders

			DoCommand(0, 0, (old_v->index << 16) | new_v->index, IsOrderListShared(old_v) ? CO_SHARE : CO_COPY, DC_EXEC, CMD_CLONE_ORDER);

			new_v->cur_order_index = old_v->cur_order_index;

			ChangeVehicleViewWindow(old_v, new_v);

			new_v->profit_this_year = old_v->profit_this_year;

			new_v->profit_last_year = old_v->profit_last_year;

			new_front = true;

			new_v->current_order = old_v->current_order;

			if (old_v->type == VEH_Train && GetNextVehicle(old_v) != NULL){

				Vehicle *temp_v = GetNextVehicle(old_v);

				// move the entire train to the new engine, excluding the old engine

				if (IsMultiheaded(old_v) && temp_v == old_v->u.rail.other_multiheaded_part) {

					// we got front and rear of a multiheaded engine right after each other. We should work with the next in line instead

					temp_v = GetNextVehicle(temp_v);

				}

				if (temp_v != NULL) {

					DoCommand(0, 0, (new_v->index << 16) | temp_v->index, 1, DC_EXEC, CMD_MOVE_RAIL_VEHICLE);

				}

			}

	}

	return cost;

}

/** replaces a vehicle if it's set for autoreplace or is too old

 * (used to be called autorenew)

 * @param v The vehicle to replace

 *	if the vehicle is a train, v needs to be the front engine

 *	return value is a pointer to the new vehicle, which is the same as the argument if nothing happened

 */

static void MaybeReplaceVehicle(Vehicle *v)

{

	Vehicle *w;

	const Player *p = GetPlayer(v->owner);

	byte flags = 0;

	int32 cost, temp_cost = 0;

	bool stopped = false;

	/* Remember the length in case we need to trim train later on

	 * If it's not a train, the value is unused */

	uint16 old_total_length = (v->type == VEH_Train) ? v->u.rail.cached_total_length : -1;

	_current_player = v->owner;

	assert(v->type == VEH_Train || v->type == VEH_Road || v->type == VEH_Ship || v->type == VEH_Aircraft);

	assert(v->vehstatus & VS_STOPPED);	// the vehicle should have been stopped in VehicleEnteredDepotThisTick() if needed

	if (v->leave_depot_instantly) {

		// we stopped the vehicle to do this, so we have to remember to start it again when we are done

		// we need to store this info as the engine might be replaced and lose this info

		stopped = true;

	}

	for (;;) {

		cost = 0;

		w = v;

		do {

			if (w->type == VEH_Train && IsMultiheaded(w) && !IsTrainEngine(w)) {

				/* we build the rear ends of multiheaded trains with the front ones */

				continue;

			}

			// check if the vehicle should be replaced

			if (!p->engine_renew ||

					w->age - w->max_age < (p->engine_renew_months * 30) || // replace if engine is too old

					w->max_age == 0) { // rail cars got a max age of 0

					continue;

			}

			/* Now replace the vehicle */

			temp_cost = ReplaceVehicle(&w, flags);

			if (flags & DC_EXEC &&

					(w->type != VEH_Train || w->u.rail.first_engine == INVALID_VEHICLE)) {

				/* now we bought a new engine and sold the old one. We need to fix the

				 * pointers in order to avoid pointing to the old one for trains: these

				 * pointers should point to the front engine and not the cars

				 */

				v = w;

			}

			if (CmdFailed(temp_cost)) break;

			cost += temp_cost;

		} while (w->type == VEH_Train && (w = GetNextVehicle(w)) != NULL);

		if (!(flags & DC_EXEC) && (CmdFailed(temp_cost) || p->money64 < (int32)(cost + p->engine_renew_money) || cost == 0)) {

			if (p->money64 < (int32)(cost + p->engine_renew_money) && ( _local_player == v->owner ) && cost != 0) {

				StringID message;

				SetDParam(0, v->unitnumber);

				switch (v->type) {

					case VEH_Train:    message = STR_TRAIN_AUTORENEW_FAILED;       break;

					case VEH_Road:     message = STR_ROADVEHICLE_AUTORENEW_FAILED; break;

					case VEH_Ship:     message = STR_SHIP_AUTORENEW_FAILED;        break;

					case VEH_Aircraft: message = STR_AIRCRAFT_AUTORENEW_FAILED;    break;

						// This should never happen

					default: NOT_REACHED(); message = 0; break;

				}

				AddNewsItem(message, NEWS_FLAGS(NM_SMALL, NF_VIEWPORT|NF_VEHICLE, NT_ADVICE, 0), v->index, 0);

			}

			if (stopped) v->vehstatus &= ~VS_STOPPED;

			_current_player = OWNER_NONE;

			return;

		}

		if (flags & DC_EXEC) {

			break;	// we are done replacing since the loop ran once with DC_EXEC

		}

		// now we redo the loop, but this time we actually do stuff since we know that we can do it

		flags |= DC_EXEC;

	}

	/* If setting is on to try not to exceed the old length of the train with the replacement */