yapf_ship_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 <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#include "../../stdafx.h"
#include "../../ship.h"
 
#include "yapf.hpp"
#include "yapf_ship_regions.h"
#include "../water_regions.h"
 
#include "../../safeguards.h"
 
static constexpr int DIRECT_NEIGHBOUR_COST = 100;
static constexpr int NODES_PER_REGION = 4;
static constexpr int MAX_NUMBER_OF_NODES = 65536;
 
static constexpr int NODE_LIST_HASH_BITS_OPEN = 12;
static constexpr int NODE_LIST_HASH_BITS_CLOSED = 12;

struct WaterRegionPatchKey {
  WaterRegionPatchDesc water_region_patch;
 
  inline void Set(const WaterRegionPatchDesc &water_region_patch)
  {
    this->water_region_patch = water_region_patch;
  }
 
  inline int CalcHash() const { return CalculateWaterRegionPatchHash(this->water_region_patch); }
  inline bool operator==(const WaterRegionPatchKey &other) const { return this->CalcHash() == other.CalcHash(); }
};
 
inline uint ManhattanDistance(const WaterRegionPatchKey &a, const WaterRegionPatchKey &b)
{
  return (std::abs(a.water_region_patch.x - b.water_region_patch.x) + std::abs(a.water_region_patch.y - b.water_region_patch.y)) * DIRECT_NEIGHBOUR_COST;
}

struct WaterRegionNode : CYapfNodeT<WaterRegionPatchKey, WaterRegionNode> {
  using Key = WaterRegionPatchKey;
  using Node = WaterRegionNode;
 
  inline void Set(Node *parent, const WaterRegionPatchDesc &water_region_patch)
  {
    this->key.Set(water_region_patch);
    this->hash_next = nullptr;
    this->parent = parent;
    this->cost = 0;
    this->estimate = 0;
  }
 
  inline void Set(Node *parent, const Key &key)
  {
    this->Set(parent, key.water_region_patch);
  }
 
  DiagDirection GetDiagDirFromParent() const
  {
    if (this->parent == nullptr) return INVALID_DIAGDIR;
    const int dx = this->key.water_region_patch.x - this->parent->key.water_region_patch.x;
    const int dy = this->key.water_region_patch.y - this->parent->key.water_region_patch.y;
    if (dx > 0 && dy == 0) return DIAGDIR_SW;
    if (dx < 0 && dy == 0) return DIAGDIR_NE;
    if (dx == 0 && dy > 0) return DIAGDIR_SE;
    if (dx == 0 && dy < 0) return DIAGDIR_NW;
    return INVALID_DIAGDIR;
  }
};
 
using WaterRegionNodeList = NodeList<WaterRegionNode, NODE_LIST_HASH_BITS_OPEN, NODE_LIST_HASH_BITS_CLOSED>;
 
/* We don't need a follower but YAPF requires one. */
struct WaterRegionFollower : public CFollowTrackWater {};
 
class YapfShipRegions;

struct WaterRegionTypes {
  using Tpf = YapfShipRegions;
  using TrackFollower = WaterRegionFollower;
  using NodeList = WaterRegionNodeList;
  using VehicleType = Ship;
};

class YapfShipRegions
  : public CYapfBaseT<WaterRegionTypes>
  , public CYapfSegmentCostCacheNoneT<WaterRegionTypes>
{
private:
  using Node = typename WaterRegionTypes::NodeList::Item;
 
  std::vector<WaterRegionPatchKey> origin_keys;
  WaterRegionPatchKey dest;
 
  inline YapfShipRegions &Yapf()
  {
    return *static_cast<YapfShipRegions *>(this);
  }
 
public:
  explicit YapfShipRegions(int max_nodes)
  {
    this->max_search_nodes = max_nodes;
  }
 
  void AddOrigin(const WaterRegionPatchDesc &water_region_patch)
  {
    if (water_region_patch.label == INVALID_WATER_REGION_PATCH) return;
    if (!HasOrigin(water_region_patch)) {
      this->origin_keys.emplace_back(water_region_patch);
      Node &node = Yapf().CreateNewNode();
      node.Set(nullptr, water_region_patch);
      Yapf().AddStartupNode(node);
    }
  }
 
  bool HasOrigin(const WaterRegionPatchDesc &water_region_patch)
  {
    return std::ranges::find(this->origin_keys, WaterRegionPatchKey{ water_region_patch }) != this->origin_keys.end();
  }
 
  void SetDestination(const WaterRegionPatchDesc &water_region_patch)
  {
    this->dest.Set(water_region_patch);
  }

  inline void PfFollowNode(Node &old_node)
  {
    VisitWaterRegionPatchCallback visit_func = [&](const WaterRegionPatchDesc &water_region_patch) {
      Node &node = Yapf().CreateNewNode();
      node.Set(&old_node, water_region_patch);
      Yapf().AddNewNode(node, TrackFollower{});
    };
    VisitWaterRegionPatchNeighbours(old_node.key.water_region_patch, visit_func);
  }

  inline bool PfDetectDestination(Node &n) const
  {
    return n.key == this->dest;
  }

  inline bool PfCalcCost(Node &n, [[maybe_unused]] const TrackFollower *follower)
  {
    n.cost = n.parent->cost + ManhattanDistance(n.key, n.parent->key);
 
    /* Incentivise zigzagging by adding a slight penalty when the search continues in the same direction. */
    Node *grandparent = n.parent->parent;
    if (grandparent != nullptr) {
      const DiagDirDiff dir_diff = DiagDirDifference(n.parent->GetDiagDirFromParent(), n.GetDiagDirFromParent());
      if (dir_diff != DIAGDIRDIFF_90LEFT && dir_diff != DIAGDIRDIFF_90RIGHT) n.cost += 1;
    }
 
    return true;
  }

  inline bool PfCalcEstimate(Node &n)
  {
    if (this->PfDetectDestination(n)) {
      n.estimate = n.cost;
      return true;
    }
 
    n.estimate = n.cost + ManhattanDistance(n.key, this->dest);
 
    return true;
  }

  inline char TransportTypeChar() const { return '^'; }

  static std::vector<WaterRegionPatchDesc> FindWaterRegionPath(const Ship *v, TileIndex start_tile, int max_returned_path_length)
  {
    const WaterRegionPatchDesc start_water_region_patch = GetWaterRegionPatchInfo(start_tile);
 
    /* We reserve 4 nodes (patches) per water region. The vast majority of water regions have 1 or 2 regions so this should be a pretty
     * safe limit. We cap the limit at 65536 which is at a region size of 16x16 is equivalent to one node per region for a 4096x4096 map. */
    const int node_limit = std::min(static_cast<int>(Map::Size() * NODES_PER_REGION) / WATER_REGION_NUMBER_OF_TILES, MAX_NUMBER_OF_NODES);
    YapfShipRegions pf(node_limit);
    pf.SetDestination(start_water_region_patch);
 
    if (v->current_order.IsType(OT_GOTO_STATION)) {
      StationID station_id = v->current_order.GetDestination().ToStationID();
      const BaseStation *station = BaseStation::Get(station_id);
      for (const auto &tile : station->GetTileArea(StationType::Dock)) {
        if (IsDockingTile(tile) && IsShipDestinationTile(tile, station_id)) {
          pf.AddOrigin(GetWaterRegionPatchInfo(tile));
        }
      }
    } else {
      TileIndex tile = v->dest_tile == INVALID_TILE ? TileIndex{} : v->dest_tile;
      pf.AddOrigin(GetWaterRegionPatchInfo(tile));
    }
 
    /* If origin and destination are the same we simply return that water patch. */
    std::vector<WaterRegionPatchDesc> path = { start_water_region_patch };
    path.reserve(max_returned_path_length);
    if (pf.HasOrigin(start_water_region_patch)) return path;
 
    /* Find best path. */
    if (!pf.FindPath(v)) return {}; // Path not found.
 
    Node *node = pf.GetBestNode();
    for (int i = 0; i < max_returned_path_length - 1; ++i) {
      if (node != nullptr) {
        node = node->parent;
        if (node != nullptr) path.push_back(node->key.water_region_patch);
      }
    }
 
    assert(!path.empty());
    return path;
  }
};

std::vector<WaterRegionPatchDesc> YapfShipFindWaterRegionPath(const Ship *v, TileIndex start_tile, int max_returned_path_length)
{
  return YapfShipRegions::FindWaterRegionPath(v, start_tile, max_returned_path_length);
}