import 'dart:math' as math;

import 'package:dartterm/algorithms/geometry.dart' as geo;
import 'package:dartterm/algorithms/regionalize.dart';
import 'package:dartterm/algorithms/kruskal.dart';
import 'package:dartterm/bitmap.dart';
import 'package:dartterm/skreek.dart';
import 'package:dartterm/world/level.dart';

part 'direction.dart';
part 'direction_set.dart';
part 'orientation.dart';
part 'requirement.dart';
part 'vault.dart';
part 'vaults.dart';

const vaultTries = 30;

class Generator {
  final math.Random _random;
  final Vaults _vaults;
  List<Vault> _queue = [];

  Generator(this._random, this._vaults);

  Level generateLevel(Requirement requirement) {
    var out = _generateOriented(requirement, false);
    return _finalize(out);
  }

  /*
  Vault generateVault(Requirement requirement) {
    var out = _generateOriented(requirement, false);
    var (vault, (_, _)) = _finalize(out);
    return vault;
  }
  */

  Vault _generateOriented(Requirement requirement, bool canBeVault) {
    if (canBeVault) {
      Vault? suggested = _suggest(vaultTries, requirement);
      if (suggested != null) {
        return _fillMetaRegions(requirement, suggested);
      }
    }

    // First of all: randomize orientation
    // This way we only have to consider one kind of spilt
    var orientation = randomOrientation(_random);

    // Try to make vx the long axis if possible
    var req2 = unReorientRequirement(requirement, orientation);
    if (req2.vyMax > (req2.vxMax - 2) * 3 / 2) {
      orientation = (orientation + 2) % 8; // rotate once more
    }
    // if only one of "left" and "right" needs to be smooth, prioritize right
    // as left is generated first
    req2 = unReorientRequirement(requirement, orientation);
    if (req2.smooth.directions.contains(Direction.left) &&
        req2.smooth.directions.contains(Direction.right)) {
      orientation = (orientation + 4) % 8;
    }

    req2 = unReorientRequirement(requirement, orientation);
    var out2 = _generateBsp(req2);
    var out1 = reorientVault(out2, orientation);

    // log("$orientation ${requirement.vx} ${requirement.vy} ${req2.vx} ${req2.vy} ${out2.vx} ${out2.vy} ${out1.vx} ${out1.vy}");
    var geo.Size(:dx, :dy) = out1.size;
    assert(dx >= requirement.vxMin && dx <= requirement.vxMax);
    assert(dy >= requirement.vyMin && dy <= requirement.vyMax);
    assert(out1.smooth.directions.containsAll(requirement.smooth.directions));
    return out1;
  }

  Vault _generateBsp(Requirement req) {
    var vxMin = req.vxMin;
    var vyMin = req.vyMin;
    var vxMax = req.vxMax;
    var vyMax = req.vyMax;

    var smoothUp = req.smooth.directions.contains(Direction.up);
    var smoothDown = req.smooth.directions.contains(Direction.down);
    var smoothUpDown = smoothUp && smoothDown;

    // var vxRand = _random.nextInt(vxMax - vxMin) + vxMin;
    var vyRand = _random.nextInt(vyMax + 1 - vyMin) + vyMin;

    if (vxMax < 2 || vyMax < 2) {
      return Vault.blank(vxMax, vyRand, VaultTile.defaultwall, req.smooth);
    } else if (vxMax < 9 || (vxMax - 2) * (vyMax - 2) < 12) {
      var v2 = Vault.blank(
          vxMax - 2, vyMax - 2, VaultTile.bspfloor, req.smooth.clone());
      var v = Vault.blank(vxMax, vyMax, VaultTile.wall, req.smooth.clone());
      v.blitFrom(v2, 1, 1);
      return v;
    } else {
      var leftReq = Requirement(
          math.max(vxMin - 4, 2), vxMax - 4, vyMin, vyMax, req.smooth.clone());
      leftReq.smooth.directions.add(Direction.right);
      var leftChild = _generateOriented(leftReq, true);

      var vyMinRight = vyMin;
      var vyMaxRight = vyMax;

      if (smoothUpDown) {
        vyMaxRight = vyMinRight = leftChild.size.dy;
      }

      var rightReq = Requirement(
        vxMin - (leftChild.vx - 1),
        vxMax - (leftChild.vx - 1),
        vyMinRight,
        vyMaxRight,
        req.smooth.clone(),
      );
      rightReq.smooth.directions.add(Direction.left);
      var rightChild = _generateOriented(rightReq, true);

      var vxTotal = leftChild.vx + rightChild.vx - 1;
      var vyTotal = math.max(leftChild.vy, rightChild.vy);

      if (smoothUp) {
        var v = Vault.blank(
            vxTotal, vyTotal, VaultTile.defaultwall, req.smooth.clone());
        v.blitFrom(leftChild, 0, 0);
        v.blitFrom(rightChild, leftChild.vx - 1, 0);
        return v;
      }
      if (smoothDown) {
        var v = Vault.blank(
            vxTotal, vyTotal, VaultTile.defaultwall, req.smooth.clone());
        v.blitFrom(leftChild, 0, vyTotal - leftChild.vy);
        v.blitFrom(rightChild, leftChild.vx - 1, vyTotal - rightChild.vy);
        return v;
      }

      // no smoothing reqs
      // min: ensure some overlap
      var vyTMax = math.min(vyMax, leftChild.vy + rightChild.vy - 3);
      if (vyTMax > vyTotal) {
        vyTotal += _random.nextInt(vyTMax - vyTotal);
      }
      var v = Vault.blank(
          vxTotal, vyTotal, VaultTile.defaultwall, req.smooth.clone());
      if (_random.nextBool()) {
        v.blitFrom(leftChild, 0, 0);
        v.blitFrom(rightChild, leftChild.vx - 1, vyTotal - rightChild.vy);
      } else {
        v.blitFrom(leftChild, 0, vyTotal - leftChild.vy);
        v.blitFrom(rightChild, leftChild.vx - 1, 0);
      }
      return v;
    }
  }

  Vault? _suggest(int tries, Requirement req) {
    for (var i = 0; i < tries; i++) {
      var sugg = _popSuggestion();
      if (sugg == null) {
        return null;
      }

      sugg = reorientVault(sugg, randomOrientation(_random));
      sugg = _tidy(sugg, req);
      if (sugg != null) {
        return sugg;
      }
    }
    return null;
  }

  Vault? _popSuggestion() {
    if (_queue.isEmpty) {
      _queue = _vaults.randomFlight(_random);
    }
    if (_queue.isEmpty) {
      return null;
    }
    return _queue.removeLast();
  }

  Vault? _tidy(Vault vault, Requirement req) {
    if (vault.vx > req.vxMax || vault.vy > req.vyMax) {
      return null;
    }
    if (vault.vx < req.vxMin || vault.vy < req.vyMin) {
      return null;
    }
    if (!vault.smooth.directions.containsAll(req.smooth.directions)) {
      return null;
    }
    // NOTE: If the vault has metaBSP regions, and they touch the outer edge, then it should be possible
    // to extend those regions
    // Extending a metaBSP region results in _two_ metaBSP regions:
    // a big version of the original, and a second one covering all the space left over
    // in the set of rows or columns the metabsp region did not touch
    //
    // Ex:
    // XXXX##
    // XXXX #
    // XXXX #
    // #    #
    // ######
    //
    // becomes
    //
    // XXXZYY
    // XXXZYY
    // XXXZYY
    // XXXX##
    // XXXX #
    // XXXX #
    // #    #
    // ######
    //
    // (where the Zs are spaces that Xs and Ys both touch)
    //
    // Extension can happen more than once, on each axis:
    //
    // XXXXXZYY
    // XXXXXZYY
    // XXXXXZYY
    // XXXXXX##
    // XXXXXX #
    // BBXXXX #
    // AA#    #
    // AA######
    //
    return vault;
  }

  Vault _fillMetaRegions(Requirement requirement, Vault vault) {
    var geo.Size(:dx, :dy) = vault.size;
    var (metaregions, _) = regionalize(geo.Rect(0, 0, dx, dy),
        (x, y) => vault.tiles.get(x, y) == VaultTile.meta0);

    for (var i in metaregions) {
      assert(i.isRectangle);
      var sz = i.rect.size;
      // TODO: Relax these based on our environs -- for instance, if one of our sides doesn't need to be smooth, that metaregion doesn't either
      var metaRequirement = Requirement(
          sz.dx,
          sz.dx,
          sz.dy,
          sz.dy,
          DirectionSet(
              {Direction.up, Direction.left, Direction.down, Direction.right}));
      var inner = _generateOriented(metaRequirement, true);
      var dest = Vault(Bitmap.blank(vault.vx, vault.vy, VaultTile.defaultwall),
          vault.smooth.clone());
      dest.blitFrom(vault, 0, 0);
      dest.blitFrom(inner, i.rect.x0, i.rect.y0);
      vault = dest;
    }

    return vault;
  }

  Level _finalize(Vault subj) {
    var vx = subj.vx, vy = subj.vy;

    var orthoOffsets = [(0, -1), (0, 1), (-1, 0), (1, 0)];

    // == build arches ==
    bool floorlike(VaultTile? tile) {
      return tile == VaultTile.bspfloor ||
          tile == VaultTile.floor ||
          tile == VaultTile.doorpronefloor ||
          tile == VaultTile.exit;
    }

    bool walkable(VaultTile? tile) {
      return tile == VaultTile.bspfloor ||
          tile == VaultTile.floor ||
          tile == VaultTile.doorpronefloor ||
          tile == VaultTile.exit ||
          tile == VaultTile.door;
    }

    List<(int, int)> newArches = [];
    for (int x = 0; x < vx; x++) {
      for (int y = 0; y < vy; y++) {
        var t = subj.tiles.get(x, y);
        if (t == VaultTile.archwall) {
          var supporters = 0;
          for (var (dx, dy) in orthoOffsets) {
            VaultTile? neighbor = subj.tiles.get(x + dx, y + dy);
            if (floorlike(neighbor)) {
              supporters++;
            }
          }

          if (supporters == 2) {
            newArches.add((x, y));
          }
          subj.tiles.set(x, y, VaultTile.wall);
        }
        if (t == VaultTile.archpronewall || t == VaultTile.defaultwall) {
          subj.tiles.set(x, y, VaultTile.wall);
        }
      }
    }

    for (var (ax, ay) in newArches) {
      subj.tiles.set(ax, ay, VaultTile.floor);
    }

    // == build doors ==
    var (regions, toRegion) =
        regionalize(geo.Rect(0, 0, subj.vx, subj.vy), (x, y) {
      return walkable(subj.tiles.get(x, y));
    });

    // generate one fake region for the exit doors to be in
    Set<(int, int)> exitRegion = {};
    for (var x = -2; x < subj.vx + 2; x++) {
      exitRegion.add((x, -1));
      exitRegion.add((x, subj.vy));
    }
    for (var y = -2; y < subj.vy + 2; y++) {
      exitRegion.add((-1, y));
      exitRegion.add((subj.vx, y));
    }

    int exitRegionId = regions.length;
    for (var (x, y) in exitRegion) {
      toRegion[(x, y)] = exitRegionId;
    }
    regions.add(Region.fromNonEmptySet(exitRegion));

    // OK: now build the doors
    double doorPoints(int x, int y) {
      return subj.tiles.get(x, y) == VaultTile.doorpronefloor ? 0.5 : 0.0;
    }

    List<Edge<(int, int)>> possibleDoors = [];
    for (var x = 0; x < subj.vx; x++) {
      for (var y = 0; y < subj.vy; y++) {
        double points;
        int region0, region1;

        if (subj.tiles.get(x, y) != VaultTile.wall) {
          continue;
        }

        var regionL = toRegion[(x - 1, y)];
        var regionR = toRegion[(x + 1, y)];
        var regionU = toRegion[(x, y - 1)];
        var regionD = toRegion[(x, y + 1)];

        if (regionL != null &&
            regionR != null &&
            regionU == null &&
            regionD == null) {
          (region0, region1) = (regionL, regionR);
          points = doorPoints(x - 1, y) + doorPoints(x + 1, y);
        } else if (regionL == null &&
            regionR == null &&
            regionU != null &&
            regionD != null) {
          (region0, region1) = (regionU, regionD);
          points = doorPoints(x, y - 1) + doorPoints(x, y + 1);
        } else {
          continue;
        }

        if (region0 == region1) {
          continue;
        }

        int roomSize = math.min(
          regions[region0].points.length,
          regions[region1].points.length,
        );

        possibleDoors.add(Edge(
            region0,
            region1,
            (x, y),
            doorScore(region0 != exitRegionId && region1 != exitRegionId,
                points, roomSize, _random.nextDouble())));
      }
    }
    List<Edge<(int, int)>> exitDoors = [];
    var minimalDoors = kruskal(regions.length, possibleDoors);
    for (var d in minimalDoors) {
      var (x, y) = d.value;
      subj.tiles.set(x, y, VaultTile.door);
      if (d.dst == exitRegionId || d.src == exitRegionId) {
        exitDoors.add(d);
      }
    }

    for (var x = 0; x < subj.vx; x++) {
      for (var y = 0; y < subj.vy; y++) {
        if (subj.tiles.get(x, y) == VaultTile.doorpronefloor) {
          subj.tiles.set(x, y, VaultTile.floor);
        }
      }
    }

    if (exitDoors.length != 1) {
      throw Exception("should be exactly one exit door");
    }

    // == Build the exit area ==
    var (exitX, exitY) = exitDoors[0].value;
    int exitVaultX, exitVaultY;
    Vault finalVault;
    int vaultBlitX, vaultBlitY;
    if (exitX == 0 || exitX == vx - 1) {
      finalVault =
          Vault.blank(vx + 3, vy, VaultTile.defaultwall, DirectionSet({}));
      vaultBlitX = exitX == 0 ? 3 : 0;
      vaultBlitY = 0;
      exitVaultX = exitX == 0 ? 1 : vx + 1;
      exitVaultY = exitY;
    } else if (exitY == 0 || exitY == vy - 1) {
      finalVault =
          Vault.blank(vx, vy + 3, VaultTile.defaultwall, DirectionSet({}));
      vaultBlitX = 0;
      vaultBlitY = exitY == 0 ? 3 : 0;
      exitVaultX = exitX;
      exitVaultY = exitY == 0 ? 1 : vy + 1;
    } else {
      throw Exception("exit door in invalid position $exitX $exitY $vx $vy");
    }

    for (var x = exitVaultX - 1; x <= exitVaultX + 1; x++) {
      for (var y = exitVaultY - 1; y <= exitVaultY + 1; y++) {
        finalVault.tiles.set(x, y, VaultTile.exit);
        if (x == exitVaultX && y == exitVaultY ||
            _manhattan(x, y, vaultBlitX + exitX, vaultBlitY + exitY) == 1) {
          finalVault.tiles.set(x, y, VaultTile.floor);
        }
      }
    }
    finalVault.blitFrom(subj, vaultBlitX, vaultBlitY);

    return Level(
        Bitmap.blankWith(finalVault.vx, finalVault.vy,
            (x, y) => flattenVaultTile(finalVault.tiles.get(x, y)!)),
        geo.Offset(exitVaultX, exitVaultY));
  }
}

// components:
// - is not exit  (exit should be placed last so it doesn't get more than one door)
// - points for placement
// - size of the underlying room
// - random factor
double doorScore(bool isNotExit, double pointsForPlacement, int roomSize,
    double randomFactor) {
  assert(pointsForPlacement >= 0.0 && pointsForPlacement <= 1.0);
  assert(roomSize >= 0 && roomSize < 100000);
  assert(randomFactor >= 0.0 && randomFactor < 1.0);
  return (isNotExit ? 1.0 : 0.0) * 1000000 +
      pointsForPlacement * 100000 +
      (100000 - roomSize).toDouble() +
      randomFactor;
}

int _manhattan(int x0, int y0, int x1, int y1) {
  return (x1 - x0).abs() + (y1 - y0).abs();
}