/**
* Check whether a ship should reverse to reach its destination.
* Called when leaving depot.
* @param v Ship
* @param tile Current position
* @param td1 Forward direction
* @param td2 Reverse direction
* @return true if the reverse direction is better
*/
static bool CheckShipReverse(const Ship *v, TileIndex tile, Trackdir td1, Trackdir td2)
{
/* get available trackdirs on the destination tile */
TrackdirBits dest_trackdirs = TrackStatusToTrackdirBits(GetTileTrackStatus(v->dest_tile, TRANSPORT_WATER, 0));
/* create pathfinder instance */
Tpf pf;
/* set origin and destination nodes */
pf.SetOrigin(tile, TrackdirToTrackdirBits(td1) | TrackdirToTrackdirBits(td2));
pf.SetDestination(v->dest_tile, dest_trackdirs);
/* find best path */
if (!pf.FindPath(v)) return false;
Node *pNode = pf.GetBestNode();
if (pNode == NULL) return false;
/* path was found
* walk through the path back to the origin */
while (pNode->m_parent != NULL) {
pNode = pNode->m_parent;
}
Trackdir best_trackdir = pNode->GetTrackdir();
assert(best_trackdir == td1 || best_trackdir == td2);
return best_trackdir == td2;
}
static Trackdir ChooseShipTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks, bool &path_found)
{
/* handle special case - when next tile is destination tile */
if (tile == v->dest_tile) {
/* convert tracks to trackdirs */
TrackdirBits trackdirs = (TrackdirBits)(tracks | ((int)tracks << 8));
/* limit to trackdirs reachable from enterdir */
trackdirs &= DiagdirReachesTrackdirs(enterdir);
/* use vehicle's current direction if that's possible, otherwise use first usable one. */
Trackdir veh_dir = v->GetVehicleTrackdir();
return ((trackdirs & TrackdirToTrackdirBits(veh_dir)) != 0) ? veh_dir : (Trackdir)FindFirstBit2x64(trackdirs);
}
/* move back to the old tile/trackdir (where ship is coming from) */
TileIndex src_tile = TILE_ADD(tile, TileOffsByDiagDir(ReverseDiagDir(enterdir)));
Trackdir trackdir = v->GetVehicleTrackdir();
assert(IsValidTrackdir(trackdir));
/* convert origin trackdir to TrackdirBits */
TrackdirBits trackdirs = TrackdirToTrackdirBits(trackdir);
/* get available trackdirs on the destination tile */
TrackdirBits dest_trackdirs = TrackStatusToTrackdirBits(GetTileTrackStatus(v->dest_tile, TRANSPORT_WATER, 0));
/* create pathfinder instance */
Tpf pf;
/* set origin and destination nodes */
pf.SetOrigin(src_tile, trackdirs);
pf.SetDestination(v->dest_tile, dest_trackdirs);
/* find best path */
path_found = pf.FindPath(v);
Trackdir next_trackdir = INVALID_TRACKDIR; // this would mean "path not found"
Node *pNode = pf.GetBestNode();
if (pNode != NULL) {
/* walk through the path back to the origin */
Node *pPrevNode = NULL;
while (pNode->m_parent != NULL) {
pPrevNode = pNode;
pNode = pNode->m_parent;
}
/* return trackdir from the best next node (direct child of origin) */
Node& best_next_node = *pPrevNode;
assert(best_next_node.GetTile() == tile);
next_trackdir = best_next_node.GetTrackdir();
}
return next_trackdir;
}