follow_track.hpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#ifndef  FOLLOW_TRACK_HPP
#define  FOLLOW_TRACK_HPP
 
#include "../pbs.h"
#include "../roadveh.h"
#include "../station_base.h"
#include "../train.h"
#include "../tunnelbridge.h"
#include "../tunnelbridge_map.h"
#include "../depot_map.h"
#include "pathfinder_func.h"

template <TransportType Ttr_type_, typename VehicleType, bool T90deg_turns_allowed_ = true, bool Tmask_reserved_tracks = false>
struct CFollowTrackT {
  enum class ErrorCode : uint8_t {
    None, 
    Owner, 
    RailRoadType, 
    SharpTurn, 
    NoWay, 
    Reserved, 
  };
 
  const VehicleType *veh; 
  Owner veh_owner; 
  TileIndex old_tile; 
  Trackdir old_td; 
  TileIndex new_tile; 
  TrackdirBits new_td_bits; 
  DiagDirection exitdir; 
  bool is_tunnel; 
  bool is_bridge; 
  bool is_station; 
  int tiles_skipped; 
  ErrorCode err;
  RailTypes railtypes;
 
  inline CFollowTrackT(const VehicleType *v = nullptr, RailTypes railtype_override = INVALID_RAILTYPES)
  {
    Init(v, railtype_override);
  }
 
  inline CFollowTrackT(Owner o, RailTypes railtype_override = INVALID_RAILTYPES)
  {
    assert(IsRailTT());
    this->veh = nullptr;
    Init(o, railtype_override);
  }
 
  inline void Init(const VehicleType *v, RailTypes railtype_override)
  {
    assert(!IsRailTT() || (v != nullptr && v->type == ::VehicleType::Train));
    this->veh = v;
    Init(v != nullptr ? v->owner : INVALID_OWNER, IsRailTT() && railtype_override == INVALID_RAILTYPES ? Train::From(v)->compatible_railtypes : railtype_override);
  }
 
  inline void Init(Owner o, RailTypes railtype_override)
  {
    assert(!IsRoadTT() || this->veh != nullptr);
    assert(!IsRailTT() || railtype_override != INVALID_RAILTYPES);
    this->veh_owner = o;
    /* don't worry, all is inlined so compiler should remove unnecessary initializations */
    this->old_tile = INVALID_TILE;
    this->old_td = Trackdir::Invalid;
    this->new_tile = INVALID_TILE;
    this->new_td_bits.Reset();
    this->exitdir = DiagDirection::Invalid;
    this->is_station = false;
    this->is_bridge = false;
    this->is_tunnel = false;
    this->tiles_skipped = 0;
    this->err = ErrorCode::None;
    this->railtypes = railtype_override;
  }
 
  [[debug_inline]] inline static TransportType TT() { return Ttr_type_; }
  [[debug_inline]] inline static bool IsWaterTT() { return TT() == TRANSPORT_WATER; }
  [[debug_inline]] inline static bool IsRailTT() { return TT() == TRANSPORT_RAIL; }
  inline bool IsTram() { return IsRoadTT() && RoadTypeIsTram(RoadVehicle::From(this->veh)->roadtype); }
  [[debug_inline]] inline static bool IsRoadTT() { return TT() == TRANSPORT_ROAD; }
  static inline bool Allow90degTurns() { return T90deg_turns_allowed_; }
  static inline bool DoTrackMasking() { return Tmask_reserved_tracks; }

  inline DiagDirection GetSingleTramBit(TileIndex tile)
  {
    assert(this->IsTram()); // this function shouldn't be called in other cases
 
    if (IsNormalRoadTile(tile)) {
      RoadBits rb = GetRoadBits(tile, RoadTramType::Tram);
      switch (rb.base()) {
        case RoadBits{RoadBit::NW}.base(): return DiagDirection::NW;
        case RoadBits{RoadBit::SW}.base(): return DiagDirection::SW;
        case RoadBits{RoadBit::SE}.base(): return DiagDirection::SE;
        case RoadBits{RoadBit::NE}.base(): return DiagDirection::NE;
        default: break;
      }
    }
    return DiagDirection::Invalid;
  }

  inline bool Follow(TileIndex old_tile, Trackdir old_td)
  {
    this->old_tile = old_tile;
    this->old_td = old_td;
    this->err = ErrorCode::None;
 
    assert([&]() {
      if (this->IsTram() && this->GetSingleTramBit(this->old_tile) != DiagDirection::Invalid) return true; // Skip the check for single tram bits
      const RoadTramType sub_mode = (IsRoadTT() && this->veh != nullptr) ? (this->IsTram() ? RoadTramType::Tram : RoadTramType::Road) : RoadTramType::Invalid;
      const TrackdirBits old_tile_valid_dirs = GetTileTrackStatus(this->old_tile, TT(), sub_mode).trackdirs;
      return old_tile_valid_dirs.Any(TrackdirToTrackdirBits(this->old_td));
    }());
 
    this->exitdir = TrackdirToExitdir(this->old_td);
    if (this->ForcedReverse()) return true;
    if (!this->CanExitOldTile()) return false;
    this->FollowTileExit();
    if (!this->QueryNewTileTrackStatus()) return TryReverse();
    this->new_td_bits &= DiagdirReachesTrackdirs(this->exitdir);
    if (this->new_td_bits.None() || !this->CanEnterNewTile()) {
      /* In case we can't enter the next tile, but are
       * a normal road vehicle, then we can actually
       * try to reverse as this is the end of the road.
       * Trams can only turn on the appropriate bits in
       * which case reaching this would mean a dead end
       * near a building and in that case there would
       * a "false" QueryNewTileTrackStatus result and
       * as such reversing is already tried. The fact
       * that function failed can have to do with a
       * missing road bit, or inability to connect the
       * different bits due to slopes. */
      if (IsRoadTT() && !this->IsTram() && this->TryReverse()) return true;
 
      /* CanEnterNewTile already set a reason.
       * Do NOT overwrite it (important for example for ErrorCode::RailRoadType).
       * Only set a reason if CanEnterNewTile was not called */
      if (this->new_td_bits.None()) this->err = ErrorCode::NoWay;
 
      return false;
    }
    if ((!IsRailTT() && !Allow90degTurns()) || (IsRailTT() && Rail90DegTurnDisallowed(GetTileRailType(this->old_tile), GetTileRailType(this->new_tile), !Allow90degTurns()))) {
      this->new_td_bits.Reset(TrackdirCrossesTrackdirs(this->old_td));
      if (this->new_td_bits.None()) {
        this->err = ErrorCode::SharpTurn;
        return false;
      }
    }
    return true;
  }
 
  inline bool MaskReservedTracks()
  {
    if (!DoTrackMasking()) return true;
 
    if (this->is_station) {
      /* Check skipped station tiles as well. */
      TileIndexDiff diff = TileOffsByDiagDir(this->exitdir);
      for (TileIndex tile = this->new_tile - diff * this->tiles_skipped; tile != this->new_tile; tile += diff) {
        if (HasStationReservation(tile)) {
          this->new_td_bits.Reset();
          this->err = ErrorCode::Reserved;
          return false;
        }
      }
    }
 
    TrackBits reserved = GetReservedTrackbits(this->new_tile);
    /* Mask already reserved trackdirs. */
    this->new_td_bits.Reset(TrackBitsToTrackdirBits(reserved));
    /* Mask out all trackdirs that conflict with the reservation. */
    for (Track t : TrackdirBitsToTrackBits(this->new_td_bits)) {
      if (TracksOverlap(reserved | t)) this->new_td_bits.Reset(TrackToTrackdirBits(t));
    }
    if (this->new_td_bits.None()) {
      this->err = ErrorCode::Reserved;
      return false;
    }
    return true;
  }
 
protected:
  inline void FollowTileExit()
  {
    this->is_station = false;
    this->is_bridge = false;
    this->is_tunnel = false;
    this->tiles_skipped = 0;
 
    /* extra handling for tunnels and bridges in our direction */
    if (IsTileType(this->old_tile, TileType::TunnelBridge)) {
      DiagDirection enterdir = GetTunnelBridgeDirection(this->old_tile);
      if (enterdir == this->exitdir) {
        /* we are entering the tunnel / bridge */
        if (IsTunnel(this->old_tile)) {
          this->is_tunnel = true;
          this->new_tile = GetOtherTunnelEnd(this->old_tile);
        } else { // IsBridge(old_tile)
          this->is_bridge = true;
          this->new_tile = GetOtherBridgeEnd(this->old_tile);
        }
        this->tiles_skipped = GetTunnelBridgeLength(this->new_tile, this->old_tile);
        return;
      }
      assert(ReverseDiagDir(enterdir) == this->exitdir);
    }
 
    /* normal or station tile, do one step */
    this->new_tile = TileAddByDiagDir(this->old_tile, this->exitdir);
 
    /* special handling for stations */
    if (IsRailTT() && HasStationTileRail(this->new_tile)) {
      this->is_station = true;
    } else if (IsRoadTT() && IsStationRoadStopTile(this->new_tile)) {
      this->is_station = true;
    }
  }

  inline bool QueryNewTileTrackStatus()
  {
    if (IsRailTT() && IsPlainRailTile(this->new_tile)) {
      this->new_td_bits = TrackBitsToTrackdirBits(GetTrackBits(this->new_tile));
    } else if (IsRoadTT()) {
      this->new_td_bits = GetTrackdirBitsForRoad(this->new_tile, this->IsTram() ? RoadTramType::Tram : RoadTramType::Road);
    } else {
      this->new_td_bits = GetTileTrackStatus(this->new_tile, TT(), RoadTramType::Invalid).trackdirs;
    }
    return this->new_td_bits.Any();
  }

  inline bool CanExitOldTile()
  {
    /* road stop can be left at one direction only unless it's a drive-through stop */
    if (IsRoadTT() && IsBayRoadStopTile(this->old_tile)) {
      DiagDirection exitdir = GetBayRoadStopDir(this->old_tile);
      if (exitdir != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
 
    /* single tram bits can only be left in one direction */
    if (this->IsTram()) {
      DiagDirection single_tram = GetSingleTramBit(this->old_tile);
      if (single_tram != DiagDirection::Invalid && single_tram != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
 
    /* road depots can be also left in one direction only */
    if (IsRoadTT() && IsDepotTypeTile(this->old_tile, TT())) {
      DiagDirection exitdir = GetRoadDepotDirection(this->old_tile);
      if (exitdir != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
    return true;
  }

  inline bool CanEnterNewTile()
  {
    if (IsRoadTT() && IsBayRoadStopTile(this->new_tile)) {
      /* road stop can be entered from one direction only unless it's a drive-through stop */
      DiagDirection exitdir = GetBayRoadStopDir(this->new_tile);
      if (ReverseDiagDir(exitdir) != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
 
    /* single tram bits can only be entered from one direction */
    if (this->IsTram()) {
      DiagDirection single_tram = this->GetSingleTramBit(this->new_tile);
      if (single_tram != DiagDirection::Invalid && single_tram != ReverseDiagDir(this->exitdir)) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
 
    /* road and rail depots can also be entered from one direction only */
    if (IsRoadTT() && IsDepotTypeTile(this->new_tile, TT())) {
      DiagDirection exitdir = GetRoadDepotDirection(this->new_tile);
      if (ReverseDiagDir(exitdir) != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
      /* don't try to enter other company's depots */
      if (GetTileOwner(this->new_tile) != this->veh_owner) {
        this->err = ErrorCode::Owner;
        return false;
      }
    }
    if (IsRailTT() && IsDepotTypeTile(this->new_tile, TT())) {
      DiagDirection exitdir = GetRailDepotDirection(this->new_tile);
      if (ReverseDiagDir(exitdir) != this->exitdir) {
        this->err = ErrorCode::NoWay;
        return false;
      }
    }
 
    /* rail transport is possible only on tiles with the same owner as vehicle */
    if (IsRailTT() && GetTileOwner(this->new_tile) != this->veh_owner) {
      /* different owner */
      this->err = ErrorCode::NoWay;
      return false;
    }
 
    /* rail transport is possible only on compatible rail types */
    if (IsRailTT() && this->railtypes.Any()) {
      RailType rail_type = GetTileRailType(this->new_tile);
      if (!this->railtypes.Test(rail_type)) {
        /* incompatible rail type */
        this->err = ErrorCode::RailRoadType;
        return false;
      }
    }
 
    /* road transport is possible only on compatible road types */
    if (IsRoadTT()) {
      const RoadVehicle *v = RoadVehicle::From(this->veh);
      RoadType roadtype = GetRoadType(this->new_tile, GetRoadTramType(v->roadtype));
      if (!v->compatible_roadtypes.Test(roadtype)) {
        /* incompatible road type */
        this->err = ErrorCode::RailRoadType;
        return false;
      }
    }
 
    /* tunnel holes and bridge ramps can be entered only from proper direction */
    if (IsTileType(this->new_tile, TileType::TunnelBridge)) {
      if (IsTunnel(this->new_tile)) {
        if (!this->is_tunnel) {
          DiagDirection tunnel_enterdir = GetTunnelBridgeDirection(this->new_tile);
          if (tunnel_enterdir != this->exitdir) {
            this->err = ErrorCode::NoWay;
            return false;
          }
        }
      } else { // IsBridge(new_tile)
        if (!this->is_bridge) {
          DiagDirection ramp_enderdir = GetTunnelBridgeDirection(this->new_tile);
          if (ramp_enderdir != this->exitdir) {
            this->err = ErrorCode::NoWay;
            return false;
          }
        }
      }
    }
 
    /* special handling for rail stations - get to the end of platform */
    if (IsRailTT() && this->is_station) {
      /* entered railway station
       * get platform length */
      uint length = BaseStation::GetByTile(this->new_tile)->GetPlatformLength(this->new_tile, TrackdirToExitdir(this->old_td));
      /* how big step we must do to get to the last platform tile? */
      this->tiles_skipped = length - 1;
      /* move to the platform end */
      TileIndexDiff diff = TileOffsByDiagDir(this->exitdir);
      diff *= this->tiles_skipped;
      this->new_tile = TileAdd(this->new_tile, diff);
      return true;
    }
 
    return true;
  }

  inline bool ForcedReverse()
  {
    /* rail and road depots cause reversing */
    if (!IsWaterTT() && IsDepotTypeTile(this->old_tile, TT())) {
      DiagDirection exitdir = IsRailTT() ? GetRailDepotDirection(this->old_tile) : GetRoadDepotDirection(this->old_tile);
      if (exitdir != this->exitdir) {
        /* reverse */
        this->new_tile = this->old_tile;
        this->new_td_bits = TrackdirToTrackdirBits(ReverseTrackdir(this->old_td));
        this->exitdir = exitdir;
        this->tiles_skipped = 0;
        this->is_tunnel = false;
        this->is_bridge = false;
        this->is_station = false;
        return true;
      }
    }
 
    /* Single tram bits and standard road stops cause reversing. */
    if (IsRoadTT() && ((this->IsTram() && GetSingleTramBit(this->old_tile) == ReverseDiagDir(this->exitdir)) ||
        (IsBayRoadStopTile(this->old_tile) && GetBayRoadStopDir(this->old_tile) == ReverseDiagDir(this->exitdir)))) {
      /* reverse */
      this->new_tile = this->old_tile;
      this->new_td_bits = TrackdirToTrackdirBits(ReverseTrackdir(this->old_td));
      this->exitdir = ReverseDiagDir(this->exitdir);
      this->tiles_skipped = 0;
      this->is_tunnel = false;
      this->is_bridge = false;
      this->is_station = false;
      return true;
    }
 
    return false;
  }

  inline bool TryReverse()
  {
    if (IsRoadTT() && !this->IsTram()) {
      /* if we reached the end of road, we can reverse the RV and continue moving */
      this->exitdir = ReverseDiagDir(this->exitdir);
      /* new tile will be the same as old one */
      this->new_tile = this->old_tile;
      /* set new trackdir bits to all reachable trackdirs */
      QueryNewTileTrackStatus();
      this->new_td_bits &= DiagdirReachesTrackdirs(this->exitdir);
      if (this->new_td_bits.Any()) {
        /* we have some trackdirs reachable after reversal */
        return true;
      }
    }
    this->err = ErrorCode::NoWay;
    return false;
  }
 
public:
  int GetSpeedLimit(int *pmin_speed = nullptr) const
  {
    int min_speed = 0;
    int max_speed = INT_MAX; // no limit
 
    /* Check for on-bridge speed limit */
    if (!IsWaterTT() && IsBridgeTile(this->old_tile)) {
      int spd = GetBridgeSpec(GetBridgeType(this->old_tile))->speed;
      if (IsRoadTT()) spd *= 2;
      max_speed = std::min(max_speed, spd);
    }
    /* Check for speed limit imposed by railtype */
    if (IsRailTT()) {
      uint16_t rail_speed = GetRailTypeInfo(GetRailType(this->old_tile))->max_speed;
      if (rail_speed > 0) max_speed = std::min<int>(max_speed, rail_speed);
    }
    if (IsRoadTT()) {
      /* max_speed is already in roadvehicle units, no need to further modify (divide by 2) */
      uint16_t road_speed = GetRoadTypeInfo(GetRoadType(this->old_tile, GetRoadTramType(RoadVehicle::From(this->veh)->roadtype)))->max_speed;
      if (road_speed > 0) max_speed = std::min<int>(max_speed, road_speed);
    }
 
    /* if min speed was requested, return it */
    if (pmin_speed != nullptr) *pmin_speed = min_speed;
    return max_speed;
  }
};
 
typedef CFollowTrackT<TRANSPORT_WATER, Ship,        true > CFollowTrackWater;
typedef CFollowTrackT<TRANSPORT_ROAD,  RoadVehicle, true > CFollowTrackRoad;
typedef CFollowTrackT<TRANSPORT_RAIL,  Train,       true > CFollowTrackRail;
 
typedef CFollowTrackT<TRANSPORT_RAIL,  Train,       false> CFollowTrackRailNo90;
 
typedef CFollowTrackT<TRANSPORT_RAIL, Train, true,  true > CFollowTrackFreeRail;
typedef CFollowTrackT<TRANSPORT_RAIL, Train, false, true > CFollowTrackFreeRailNo90;
 
#endif /* FOLLOW_TRACK_HPP */