part of 'sitemode.dart';

const double fovMaxMovementCost = 10.0;
const double fovMaxMemoryDistance = 80.0;

extension FOVParts on SiteMode {
  void fovMaintain() {
    fovVisible = {};
    shadowcast(playerPosition, _fovIsBlocking, (xy) => fovVisible.add(xy));

    var oldFovMemory = fovMemory;
    fovMemory = {};
    oldFovMemory.addAll(fovVisible);
    for (var xy in oldFovMemory) {
      if (_fovMemorablyClose(xy)) {
        fovMemory.add(xy);
      }
    }

    fovMovable = {};
    for (var r in dijkstra<geo.Offset>(playerPosition, _fovDijkstraNeighbors)) {
      if (r.cost > fovMaxMovementCost) {
        break;
      }
      fovMovable.add(r.item);
    }
  }

  bool _fovMemorablyClose(geo.Offset other) {
    var dx = (other.x - playerPosition.x).toDouble();
    var dy = (other.y - playerPosition.y).toDouble();
    return math.sqrt(dx * dx + dy * dy) < fovMaxMemoryDistance;
  }

  bool _fovKnown(geo.Offset other) {
    return fovVisible.contains(other) || fovMemory.contains(other);
  }

  bool _fovIsBlocking(geo.Offset xy) {
    switch (level.tiles.get(xy.x, xy.y)) {
      case null:
        return true;
      case LevelTile.exit:
        return true;
      case LevelTile.openDoor:
      case LevelTile.floor:
        return false;
      case LevelTile.wall:
        return true;
      case LevelTile.closedDoor:
        return true;
    }
  }

  Iterable<Edge<geo.Offset>> _fovDijkstraNeighbors(geo.Offset xy) sync* {
    var tile = level.tiles.get(xy.x, xy.y);
    if (tile == LevelTile.exit || tile == LevelTile.closedDoor) {
      // can't go anywhere after this
      return;
    }

    for (var (dx, dy) in [(-1, 0), (1, 0), (0, -1), (0, 1)]) {
      var xy2 = geo.Offset(xy.x + dx, xy.y + dy);

      // Only return visible or remembered tiles
      if (!_fovKnown(xy2)) {
        continue;
      }

      var tile = level.tiles.get(xy2.x, xy2.y);
      if (tile == LevelTile.wall) {
        continue;
      }
      // for now, because exiting isn't implemented
      if (tile == LevelTile.exit) {
        continue;
      }
      yield Edge(1.0, xy2);
    }
  }
}