yapf_river_builder.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 "../../water.h"
#include "../../genworld.h"
#include "yapf.hpp"
 
#include "../../safeguards.h"
 
/* River builder pathfinder node. */
struct YapfRiverBuilderNode : CYapfNodeT<CYapfNodeKeyTrackDir, YapfRiverBuilderNode> {};

using RiverBuilderNodeList = NodeList<YapfRiverBuilderNode, 8, 10>;
 
/* We don't need a follower but YAPF requires one. */
struct RiverBuilderFollower {};
 
/* We don't need a vehicle but YAPF requires one. */
struct DummyVehicle : Vehicle {};
 
class YapfRiverBuilder;

struct RiverBuilderTypes {
  using Tpf = YapfRiverBuilder;
  using TrackFollower = RiverBuilderFollower;
  using NodeList = RiverBuilderNodeList;
  using VehicleType = DummyVehicle;
};

class YapfRiverBuilder
  : public CYapfBaseT<RiverBuilderTypes>
  , public CYapfSegmentCostCacheNoneT<RiverBuilderTypes>
{
public:
  using Node = RiverBuilderTypes::NodeList::Item;
  using Key = Node::Key;
 
protected:
  TileIndex end_tile; 
 
  inline YapfRiverBuilder &Yapf()
  {
    return *static_cast<YapfRiverBuilder *>(this);
  }
 
public:
  YapfRiverBuilder(TileIndex start_tile, TileIndex end_tile)
  {
    this->end_tile = end_tile;
 
    Node &node = Yapf().CreateNewNode();
    node.Set(nullptr, start_tile, INVALID_TRACKDIR, false);
    Yapf().AddStartupNode(node);
  }

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

  inline bool PfCalcCost(Node &n, [[maybe_unused]] const RiverBuilderFollower *follower)
  {
    n.cost = n.parent->cost + 1 + RandomRange(_settings_game.game_creation.river_route_random);
    return true;
  }

  inline bool PfCalcEstimate(Node &n)
  {
    n.estimate = n.cost + DistanceManhattan(this->end_tile, n.GetTile());
    assert(n.estimate >= n.parent->estimate);
    return true;
  }

  inline void PfFollowNode(Node &old_node)
  {
    for (DiagDirection d = DIAGDIR_BEGIN; d < DIAGDIR_END; ++d) {
      const TileIndex t = old_node.GetTile() + TileOffsByDiagDir(d);
      if (IsValidTile(t) && RiverFlowsDown(old_node.GetTile(), t)) {
        Node &node = Yapf().CreateNewNode();
        node.Set(&old_node, t, INVALID_TRACKDIR, true);
        Yapf().AddNewNode(node, RiverBuilderFollower{});
      }
    }
  }

  inline char TransportTypeChar() const
  {
    return '~';
  }
 
  static void BuildRiver(TileIndex start_tile, TileIndex end_tile, TileIndex spring_tile, bool main_river)
  {
    YapfRiverBuilder pf(start_tile, end_tile);
    if (pf.FindPath(nullptr) == false) return; // No path found
 
    /* First, build the river without worrying about its width. */
    for (Node *node = pf.GetBestNode(); node != nullptr; node = node->parent) {
      TileIndex tile = node->GetTile();
      if (!IsWaterTile(tile)) {
        MakeRiverAndModifyDesertZoneAround(tile);
      }
    }
 
    /* If the river is a main river, go back along the path to widen it.
     * Don't make wide rivers if we're using the original landscape generator.
     */
    if (_settings_game.game_creation.land_generator != LG_ORIGINAL && main_river) {
      const uint long_river_length = _settings_game.game_creation.min_river_length * 4;
 
      for (Node *node = pf.GetBestNode(); node != nullptr; node = node->parent) {
        const TileIndex center_tile = node->GetTile();
 
        /* Check if we should widen river depending on how far we are away from the source. */
        uint current_river_length = DistanceManhattan(spring_tile, center_tile);
        uint diameter = std::min(3u, (current_river_length / (long_river_length / 3u)) + 1u);
        if (diameter <= 1) continue;
 
        for (auto tile : SpiralTileSequence(center_tile, diameter)) {
          RiverMakeWider(tile, center_tile);
        }
      }
    }
  }
};

void YapfBuildRiver(TileIndex start_tile, TileIndex end_tile, TileIndex spring_tile, bool main_river)
{
  YapfRiverBuilder::BuildRiver(start_tile, end_tile, spring_tile, main_river);
}