water_regions.cpp

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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 <http://www.gnu.org/licenses/>.
 */
 
#include "stdafx.h"
#include "map_func.h"
#include "water_regions.h"
#include "map_func.h"
#include "tilearea_type.h"
#include "track_func.h"
#include "transport_type.h"
#include "landscape.h"
#include "tunnelbridge_map.h"
#include "follow_track.hpp"
#include "ship.h"
#include "debug.h"
 
using TWaterRegionTraversabilityBits = uint16_t;
constexpr TWaterRegionPatchLabel FIRST_REGION_LABEL = 1;
constexpr TWaterRegionPatchLabel INVALID_WATER_REGION_PATCH = 0;
 
static_assert(sizeof(TWaterRegionTraversabilityBits) * 8 == WATER_REGION_EDGE_LENGTH);
static_assert(sizeof(TWaterRegionPatchLabel) == sizeof(byte)); // Important for the hash calculation.
 
static inline TrackBits GetWaterTracks(TileIndex tile) { return TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_WATER, 0)); }
static inline bool IsAqueductTile(TileIndex tile) { return IsBridgeTile(tile) && GetTunnelBridgeTransportType(tile) == TRANSPORT_WATER; }
 
static inline int GetWaterRegionX(TileIndex tile) { return TileX(tile) / WATER_REGION_EDGE_LENGTH; }
static inline int GetWaterRegionY(TileIndex tile) { return TileY(tile) / WATER_REGION_EDGE_LENGTH; }
 
static inline int GetWaterRegionMapSizeX() { return Map::SizeX() / WATER_REGION_EDGE_LENGTH; }
static inline int GetWaterRegionMapSizeY() { return Map::SizeY() / WATER_REGION_EDGE_LENGTH; }
 
static inline TWaterRegionIndex GetWaterRegionIndex(int region_x, int region_y) { return GetWaterRegionMapSizeX() * region_y + region_x; }
static inline TWaterRegionIndex GetWaterRegionIndex(TileIndex tile) { return GetWaterRegionIndex(GetWaterRegionX(tile), GetWaterRegionY(tile)); }
 
class WaterRegion
{
private:
  std::array<TWaterRegionTraversabilityBits, DIAGDIR_END> edge_traversability_bits{};
  bool has_cross_region_aqueducts = false;
  TWaterRegionPatchLabel number_of_patches = 0; // 0 = no water, 1 = one single patch of water, etc...
  const OrthogonalTileArea tile_area;
  std::array<TWaterRegionPatchLabel, WATER_REGION_NUMBER_OF_TILES> tile_patch_labels{};
  bool initialized = false;
 
  inline int GetLocalIndex(TileIndex tile) const
  {
    assert(this->tile_area.Contains(tile));
    return (TileX(tile) - TileX(this->tile_area.tile)) + WATER_REGION_EDGE_LENGTH * (TileY(tile) - TileY(this->tile_area.tile));
  }
 
public:
  WaterRegion(int region_x, int region_y)
    : tile_area(TileXY(region_x * WATER_REGION_EDGE_LENGTH, region_y * WATER_REGION_EDGE_LENGTH), WATER_REGION_EDGE_LENGTH, WATER_REGION_EDGE_LENGTH)
  {}
 
  OrthogonalTileIterator begin() const { return this->tile_area.begin(); }
  OrthogonalTileIterator end() const { return this->tile_area.end(); }
 
  bool IsInitialized() const { return this->initialized; }
 
  void Invalidate() { this->initialized = false; }
 
  TWaterRegionTraversabilityBits GetEdgeTraversabilityBits(DiagDirection side) const { return edge_traversability_bits[side]; }
 
  int NumberOfPatches() const { return this->number_of_patches; }
 
  bool HasCrossRegionAqueducts() const { return this->has_cross_region_aqueducts; }
 
  TWaterRegionPatchLabel GetLabel(TileIndex tile) const
  {
    assert(this->tile_area.Contains(tile));
    return this->tile_patch_labels[GetLocalIndex(tile)];
  }
 
  void ForceUpdate()
  {
    Debug(map, 3, "Updating water region ({},{})", GetWaterRegionX(this->tile_area.tile), GetWaterRegionY(this->tile_area.tile));
    this->has_cross_region_aqueducts = false;
 
    this->tile_patch_labels.fill(INVALID_WATER_REGION_PATCH);
 
    for (const TileIndex tile : this->tile_area) {
      if (IsAqueductTile(tile)) {
        const TileIndex other_aqueduct_end = GetOtherBridgeEnd(tile);
        if (!tile_area.Contains(other_aqueduct_end)) {
          this->has_cross_region_aqueducts = true;
          break;
        }
      }
    }
 
    TWaterRegionPatchLabel current_label = 1;
    TWaterRegionPatchLabel highest_assigned_label = 0;
 
    /* Perform connected component labeling. This uses a flooding algorithm that expands until no
     * additional tiles can be added. Only tiles inside the water region are considered. */
    for (const TileIndex start_tile : tile_area) {
      static std::vector<TileIndex> tiles_to_check;
      tiles_to_check.clear();
      tiles_to_check.push_back(start_tile);
 
      bool increase_label = false;
      while (!tiles_to_check.empty()) {
        const TileIndex tile = tiles_to_check.back();
        tiles_to_check.pop_back();
 
        const TrackdirBits valid_dirs = TrackBitsToTrackdirBits(GetWaterTracks(tile));
        if (valid_dirs == TRACKDIR_BIT_NONE) continue;
 
        if (this->tile_patch_labels[GetLocalIndex(tile)] != INVALID_WATER_REGION_PATCH) continue;
 
        this->tile_patch_labels[GetLocalIndex(tile)] = current_label;
        highest_assigned_label = current_label;
        increase_label = true;
 
        for (const Trackdir dir : SetTrackdirBitIterator(valid_dirs)) {
          /* By using a TrackFollower we "play by the same rules" as the actual ship pathfinder */
          CFollowTrackWater ft;
          if (ft.Follow(tile, dir) && this->tile_area.Contains(ft.m_new_tile)) tiles_to_check.push_back(ft.m_new_tile);
        }
      }
 
      if (increase_label) current_label++;
    }
 
    this->number_of_patches = highest_assigned_label;
    this->initialized = true;
 
    /* Calculate the traversability (whether the tile can be entered / exited) for all edges. Note that
     * we always follow the same X and Y scanning direction, this is important for comparisons later on! */
    this->edge_traversability_bits.fill(0);
    const int top_x = TileX(tile_area.tile);
    const int top_y = TileY(tile_area.tile);
    for (int i = 0; i < WATER_REGION_EDGE_LENGTH; ++i) {
      if (GetWaterTracks(TileXY(top_x + i, top_y)) & TRACK_BIT_3WAY_NW) SetBit(this->edge_traversability_bits[DIAGDIR_NW], i); // NW edge
      if (GetWaterTracks(TileXY(top_x + i, top_y + WATER_REGION_EDGE_LENGTH - 1)) & TRACK_BIT_3WAY_SE) SetBit(this->edge_traversability_bits[DIAGDIR_SE], i); // SE edge
      if (GetWaterTracks(TileXY(top_x, top_y + i)) & TRACK_BIT_3WAY_NE) SetBit(this->edge_traversability_bits[DIAGDIR_NE], i); // NE edge
      if (GetWaterTracks(TileXY(top_x + WATER_REGION_EDGE_LENGTH - 1, top_y + i)) & TRACK_BIT_3WAY_SW) SetBit(this->edge_traversability_bits[DIAGDIR_SW], i); // SW edge
    }
  }
 
  inline void UpdateIfNotInitialized()
  {
    if (!this->initialized) ForceUpdate();
  }
};
 
std::vector<WaterRegion> _water_regions;
 
TileIndex GetTileIndexFromLocalCoordinate(int region_x, int region_y, int local_x, int local_y)
{
  assert(local_x >= 0 && local_x < WATER_REGION_EDGE_LENGTH);
  assert(local_y >= 0 && local_y < WATER_REGION_EDGE_LENGTH);
  return TileXY(WATER_REGION_EDGE_LENGTH * region_x + local_x, WATER_REGION_EDGE_LENGTH * region_y + local_y);
}
 
TileIndex GetEdgeTileCoordinate(int region_x, int region_y, DiagDirection side, int x_or_y)
{
  assert(x_or_y >= 0 && x_or_y < WATER_REGION_EDGE_LENGTH);
  switch (side) {
    case DIAGDIR_NE: return GetTileIndexFromLocalCoordinate(region_x, region_y, 0, x_or_y);
    case DIAGDIR_SW: return GetTileIndexFromLocalCoordinate(region_x, region_y, WATER_REGION_EDGE_LENGTH - 1, x_or_y);
    case DIAGDIR_NW: return GetTileIndexFromLocalCoordinate(region_x, region_y, x_or_y, 0);
    case DIAGDIR_SE: return GetTileIndexFromLocalCoordinate(region_x, region_y, x_or_y, WATER_REGION_EDGE_LENGTH - 1);
    default: NOT_REACHED();
  }
}
 
WaterRegion &GetUpdatedWaterRegion(uint16_t region_x, uint16_t region_y)
{
  WaterRegion &result = _water_regions[GetWaterRegionIndex(region_x, region_y)];
  result.UpdateIfNotInitialized();
  return result;
}
 
WaterRegion &GetUpdatedWaterRegion(TileIndex tile)
{
  WaterRegion &result = _water_regions[GetWaterRegionIndex(tile)];
  result.UpdateIfNotInitialized();
  return result;
}
 
TWaterRegionIndex GetWaterRegionIndex(const WaterRegionDesc &water_region)
{
  return GetWaterRegionIndex(water_region.x, water_region.y);
}
 
int CalculateWaterRegionPatchHash(const WaterRegionPatchDesc &water_region_patch)
{
  return water_region_patch.label | GetWaterRegionIndex(water_region_patch) << 8;
}
 
TileIndex GetWaterRegionCenterTile(const WaterRegionDesc &water_region)
{
  return TileXY(water_region.x * WATER_REGION_EDGE_LENGTH + (WATER_REGION_EDGE_LENGTH / 2), water_region.y * WATER_REGION_EDGE_LENGTH + (WATER_REGION_EDGE_LENGTH / 2));
}
 
WaterRegionDesc GetWaterRegionInfo(TileIndex tile)
{
  return WaterRegionDesc{ GetWaterRegionX(tile), GetWaterRegionY(tile) };
}
 
WaterRegionPatchDesc GetWaterRegionPatchInfo(TileIndex tile)
{
  WaterRegion &region = GetUpdatedWaterRegion(tile);
  return WaterRegionPatchDesc{ GetWaterRegionX(tile), GetWaterRegionY(tile), region.GetLabel(tile)};
}
 
void InvalidateWaterRegion(TileIndex tile)
{
  const int index = GetWaterRegionIndex(tile);
  _water_regions[index].Invalidate();
 
  Debug(map, 3, "Invalidated water region ({},{})", GetWaterRegionX(tile), GetWaterRegionY(tile));
}
 
static inline void VisitAdjacentWaterRegionPatchNeighbors(const WaterRegionPatchDesc &water_region_patch, DiagDirection side, TVisitWaterRegionPatchCallBack &func)
{
  const WaterRegion &current_region = GetUpdatedWaterRegion(water_region_patch.x, water_region_patch.y);
 
  const TileIndexDiffC offset = TileIndexDiffCByDiagDir(side);
  const int nx = water_region_patch.x + offset.x;
  const int ny = water_region_patch.y + offset.y;
 
  if (nx < 0 || ny < 0 || nx >= GetWaterRegionMapSizeX() || ny >= GetWaterRegionMapSizeY()) return;
 
  const WaterRegion &neighboring_region = GetUpdatedWaterRegion(nx, ny);
  const DiagDirection opposite_side = ReverseDiagDir(side);
 
  /* Indicates via which local x or y coordinates (depends on the "side" parameter) we can cross over into the adjacent region. */
  const TWaterRegionTraversabilityBits traversability_bits = current_region.GetEdgeTraversabilityBits(side)
    & neighboring_region.GetEdgeTraversabilityBits(opposite_side);
  if (traversability_bits == 0) return;
 
  if (current_region.NumberOfPatches() == 1 && neighboring_region.NumberOfPatches() == 1) {
    func(WaterRegionPatchDesc{ nx, ny, FIRST_REGION_LABEL }); // No further checks needed because we know there is just one patch for both adjacent regions
    return;
  }
 
  /* Multiple water patches can be reached from the current patch. Check each edge tile individually. */
  static std::vector<TWaterRegionPatchLabel> unique_labels; // static and vector-instead-of-map for performance reasons
  unique_labels.clear();
  for (int x_or_y = 0; x_or_y < WATER_REGION_EDGE_LENGTH; ++x_or_y) {
    if (!HasBit(traversability_bits, x_or_y)) continue;
 
    const TileIndex current_edge_tile = GetEdgeTileCoordinate(water_region_patch.x, water_region_patch.y, side, x_or_y);
    const TWaterRegionPatchLabel current_label = current_region.GetLabel(current_edge_tile);
    if (current_label != water_region_patch.label) continue;
 
    const TileIndex neighbor_edge_tile = GetEdgeTileCoordinate(nx, ny, opposite_side, x_or_y);
    const TWaterRegionPatchLabel neighbor_label = neighboring_region.GetLabel(neighbor_edge_tile);
    if (std::find(unique_labels.begin(), unique_labels.end(), neighbor_label) == unique_labels.end()) unique_labels.push_back(neighbor_label);
  }
  for (TWaterRegionPatchLabel unique_label : unique_labels) func(WaterRegionPatchDesc{ nx, ny, unique_label });
}
 
void VisitWaterRegionPatchNeighbors(const WaterRegionPatchDesc &water_region_patch, TVisitWaterRegionPatchCallBack &callback)
{
  const WaterRegion &current_region = GetUpdatedWaterRegion(water_region_patch.x, water_region_patch.y);
 
  /* Visit adjacent water region patches in each cardinal direction */
  for (DiagDirection side = DIAGDIR_BEGIN; side < DIAGDIR_END; side++) VisitAdjacentWaterRegionPatchNeighbors(water_region_patch, side, callback);
 
  /* Visit neigboring water patches accessible via cross-region aqueducts */
  if (current_region.HasCrossRegionAqueducts()) {
    for (const TileIndex tile : current_region) {
      if (GetWaterRegionPatchInfo(tile) == water_region_patch && IsAqueductTile(tile)) {
        const TileIndex other_end_tile = GetOtherBridgeEnd(tile);
        if (GetWaterRegionIndex(tile) != GetWaterRegionIndex(other_end_tile)) callback(GetWaterRegionPatchInfo(other_end_tile));
      }
    }
  }
}
 
void AllocateWaterRegions()
{
  _water_regions.clear();
  _water_regions.reserve(static_cast<size_t>(GetWaterRegionMapSizeX()) * GetWaterRegionMapSizeY());
 
  Debug(map, 2, "Allocating {} x {} water regions", GetWaterRegionMapSizeX(), GetWaterRegionMapSizeY());
 
  for (int region_y = 0; region_y < GetWaterRegionMapSizeY(); region_y++) {
    for (int region_x = 0; region_x < GetWaterRegionMapSizeX(); region_x++) {
      _water_regions.emplace_back(region_x, region_y);
    }
  }
}