Reverse behind signal pathfinding now takes into account train length

This is to avoid pathfinding into a reversing track section which
is too short

src/pathfinder/yapf/yapf_costrail.hpp

@@ -685,6 +685,7 @@ no_entry_cost: // jump here at the beginning if the node has no parent (it is th
 			if (!tf_local.Follow(cur.tile, cur.td)) {
 				assert(tf_local.m_err != TrackFollower::EC_NONE);
 				/* Can't move to the next tile (EOL?). */
+				if (!(end_segment_reason & (ESRB_RAIL_TYPE | ESRB_DEAD_END))) end_segment_reason |= ESRB_DEAD_END_EOL;
 				if (tf_local.m_err == TrackFollower::EC_RAIL_ROAD_TYPE) {
 					end_segment_reason |= ESRB_RAIL_TYPE;
 				} else {

src/pathfinder/yapf/yapf_node_rail.hpp

@@ -215,6 +215,35 @@ struct CYapfRailNodeT
 		return (obj.*func)(cur, cur_td);
 	}
 
+	template <class Tbase, class Tpf>
+	uint GetNodeLength(const Train *v, Tpf &yapf, Tbase &obj) const
+	{
+		typename Tbase::TrackFollower ft(v, yapf.GetCompatibleRailTypes());
+		TileIndex cur = base::GetTile();
+		Trackdir  cur_td = base::GetTrackdir();
+
+		uint length = 0;
+
+		while (cur != GetLastTile() || cur_td != GetLastTrackdir()) {
+			length += IsDiagonalTrackdir(cur_td) ? TILE_SIZE : (TILE_SIZE / 2);
+			if (!ft.Follow(cur, cur_td)) break;
+			length += TILE_SIZE * ft.m_tiles_skipped;
+			cur = ft.m_new_tile;
+			assert(KillFirstBit(ft.m_new_td_bits) == TRACKDIR_BIT_NONE);
+			cur_td = FindFirstTrackdir(ft.m_new_td_bits);
+		}
+
+		EndSegmentReasonBits esrb = this->m_segment->m_end_segment_reason;
+		if (!(esrb & ESRB_DEAD_END) || (esrb & ESRB_DEAD_END_EOL)) {
+			length += IsDiagonalTrackdir(cur_td) ? TILE_SIZE : (TILE_SIZE / 2);
+			if (IsTileType(cur, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationEntrance(cur) && TrackdirEntersTunnelBridge(cur, cur_td)) {
+				length += TILE_SIZE * GetTunnelBridgeLength(cur, GetOtherTunnelBridgeEnd(cur));
+			}
+		}
+
+		return length;
+	}
+
 	void Dump(DumpTarget &dmp) const
 	{
 		base::Dump(dmp);

src/pathfinder/yapf/yapf_rail.cpp

@@ -289,13 +289,16 @@ public:
 	 */
 	inline void PfFollowNode(Node &old_node)
 	{
-		TrackFollower F(Yapf().GetVehicle());
+		const Train *v = Yapf().GetVehicle();
+		TrackFollower F(v);
 		if (old_node.flags_u.flags_s.m_reverse_pending && old_node.m_segment->m_end_segment_reason & (ESRB_SAFE_TILE | ESRB_DEPOT | ESRB_DEAD_END)) {
 			Node *rev_node = &old_node;
+			uint length = 0;
 			while (rev_node && !(rev_node->m_segment->m_end_segment_reason & ESRB_REVERSE)) {
+				length += rev_node->GetNodeLength(v, Yapf(), *this);
 				rev_node = rev_node->m_parent;
 			}
-			if (rev_node) {
+			if (rev_node && length >= v->gcache.cached_total_length) {
 				if (F.Follow(rev_node->GetLastTile(), ReverseTrackdir(rev_node->GetLastTrackdir()))) {
 					Yapf().AddMultipleNodes(&old_node, F, [&](Node &n) {
 						n.flags_u.flags_s.m_reverse_pending = false;
@@ -303,6 +306,8 @@ public:
 					});
 				}
 				return;
+			} else if (old_node.m_segment->m_end_segment_reason & (ESRB_DEPOT | ESRB_DEAD_END)) {
+				return;
 			}
 		}
 		if (F.Follow(old_node.GetLastTile(), old_node.GetLastTrackdir())) {
@@ -482,13 +487,16 @@ public:
 	 */
 	inline void PfFollowNode(Node &old_node)
 	{
-		TrackFollower F(Yapf().GetVehicle());
+		const Train *v = Yapf().GetVehicle();
+		TrackFollower F(v);
 		if (old_node.flags_u.flags_s.m_reverse_pending && old_node.m_segment->m_end_segment_reason & (ESRB_SAFE_TILE | ESRB_DEPOT | ESRB_DEAD_END)) {
 			Node *rev_node = &old_node;
+			uint length = 0;
 			while (rev_node && !(rev_node->m_segment->m_end_segment_reason & ESRB_REVERSE)) {
+				length += rev_node->GetNodeLength(v, Yapf(), *this);
 				rev_node = rev_node->m_parent;
 			}
-			if (rev_node) {
+			if (rev_node && length >= v->gcache.cached_total_length) {
 				if (F.Follow(rev_node->GetLastTile(), ReverseTrackdir(rev_node->GetLastTrackdir()))) {
 					Yapf().AddMultipleNodes(&old_node, F, [&](Node &n) {
 						n.flags_u.flags_s.m_reverse_pending = false;
@@ -496,6 +504,8 @@ public:
 					});
 				}
 				return;
+			} else if (old_node.m_segment->m_end_segment_reason & (ESRB_DEPOT | ESRB_DEAD_END)) {
+				return;
 			}
 		}
 		if (F.Follow(old_node.GetLastTile(), old_node.GetLastTrackdir())) {

src/pathfinder/yapf/yapf_type.hpp

@@ -17,6 +17,7 @@
 enum EndSegmentReason {
 	/* The following reasons can be saved into cached segment */
 	ESR_DEAD_END = 0,      ///< track ends here
+	ESR_DEAD_END_EOL,      ///< track ends here bit refers to the next tile, the last tile of the segment itself is usable
 	ESR_RAIL_TYPE,         ///< the next tile has a different rail type than our tiles
 	ESR_INFINITE_LOOP,     ///< infinite loop detected
 	ESR_SEGMENT_TOO_LONG,  ///< the segment is too long (possible infinite loop)
@@ -42,6 +43,7 @@ enum EndSegmentReasonBits {
 	ESRB_NONE = 0,
 
 	ESRB_DEAD_END          = 1 << ESR_DEAD_END,
+	ESRB_DEAD_END_EOL      = 1 << ESR_DEAD_END_EOL,
 	ESRB_RAIL_TYPE         = 1 << ESR_RAIL_TYPE,
 	ESRB_INFINITE_LOOP     = 1 << ESR_INFINITE_LOOP,
 	ESRB_SEGMENT_TOO_LONG  = 1 << ESR_SEGMENT_TOO_LONG,
@@ -63,7 +65,7 @@ enum EndSegmentReasonBits {
 	ESRB_POSSIBLE_TARGET = ESRB_DEPOT | ESRB_WAYPOINT | ESRB_STATION | ESRB_SAFE_TILE,
 
 	/* What reasons can be stored back into cached segment. */
-	ESRB_CACHED_MASK = ESRB_DEAD_END | ESRB_RAIL_TYPE | ESRB_INFINITE_LOOP | ESRB_SEGMENT_TOO_LONG | ESRB_CHOICE_FOLLOWS | ESRB_DEPOT | ESRB_WAYPOINT | ESRB_STATION | ESRB_SAFE_TILE | ESRB_REVERSE,
+	ESRB_CACHED_MASK = ESRB_DEAD_END | ESRB_DEAD_END_EOL | ESRB_RAIL_TYPE | ESRB_INFINITE_LOOP | ESRB_SEGMENT_TOO_LONG | ESRB_CHOICE_FOLLOWS | ESRB_DEPOT | ESRB_WAYPOINT | ESRB_STATION | ESRB_SAFE_TILE | ESRB_REVERSE,
 
 	/* Reasons to abort pathfinding in this direction. */
 	ESRB_ABORT_PF_MASK = ESRB_DEAD_END | ESRB_PATH_TOO_LONG | ESRB_INFINITE_LOOP | ESRB_FIRST_TWO_WAY_RED,
@@ -77,7 +79,7 @@ DECLARE_ENUM_AS_BIT_SET(EndSegmentReasonBits)
 inline std::string ValueStr(EndSegmentReasonBits bits)
 {
 	static const char * const end_segment_reason_names[] = {
-		"DEAD_END", "RAIL_TYPE", "INFINITE_LOOP", "SEGMENT_TOO_LONG", "CHOICE_FOLLOWS",
+		"DEAD_END", "DEAD_END_EOL", "RAIL_TYPE", "INFINITE_LOOP", "SEGMENT_TOO_LONG", "CHOICE_FOLLOWS",
 		"DEPOT", "WAYPOINT", "STATION", "SAFE_TILE",
 		"PATH_TOO_LONG", "FIRST_TWO_WAY_RED", "LOOK_AHEAD_END", "TARGET_REACHED",
 		"REVERSE"