/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule GameBoard
 * @flow
 */
'use strict';

// NB: Taken straight from: https://github.com/IvanVergiliev/2048-react/blob/master/src/board.js
//     with no modificiation except to format it for CommonJS and fix lint/flow errors

var rotateLeft = function (matrix) {
  var rows = matrix.length;
  var columns = matrix[0].length;
  var res = [];
  for (var row = 0; row < rows; ++row) {
    res.push([]);
    for (var column = 0; column < columns; ++column) {
      res[row][column] = matrix[column][columns - row - 1];
    }
  }
  return res;
};

var Tile = function (value?: number, row?: number, column?: number) {
  this.value = value || 0;
  this.row = row || -1;

  this.column = column || -1;
  this.oldRow = -1;
  this.oldColumn = -1;
  this.markForDeletion = false;
  this.mergedInto = null;
  this.id = Tile.id++;
};

Tile.id = 0;

Tile.prototype.moveTo = function (row, column) {
  this.oldRow = this.row;
  this.oldColumn = this.column;
  this.row = row;
  this.column = column;
};

Tile.prototype.isNew = function () {
  return this.oldRow === -1 && !this.mergedInto;
};

Tile.prototype.hasMoved = function () {
  return (this.fromRow() !== -1 && (this.fromRow() !== this.toRow() || this.fromColumn() !== this.toColumn())) ||
    this.mergedInto;
};

Tile.prototype.fromRow = function () {
  return this.mergedInto ? this.row : this.oldRow;
};

Tile.prototype.fromColumn = function () {
  return this.mergedInto ? this.column : this.oldColumn;
};

Tile.prototype.toRow = function () {
  return this.mergedInto ? this.mergedInto.row : this.row;
};

Tile.prototype.toColumn = function () {
  return this.mergedInto ? this.mergedInto.column : this.column;
};

var Board = function () {
  this.tiles = [];
  this.cells = [];
  for (var i = 0; i < Board.size; ++i) {
    this.cells[i] = [this.addTile(), this.addTile(), this.addTile(), this.addTile()];
  }
  this.addRandomTile();
  this.setPositions();
  this.won = false;
};

Board.prototype.addTile = function () {
  var res = new Tile();
  Tile.apply(res, arguments);
  this.tiles.push(res);
  return res;
};

Board.size = 4;

Board.prototype.moveLeft = function () {
  var hasChanged = false;
  for (var row = 0; row < Board.size; ++row) {
    var currentRow = this.cells[row].filter(function (tile) { return tile.value !== 0; });
    var resultRow = [];
    for (var target = 0; target < Board.size; ++target) {
      var targetTile = currentRow.length ? currentRow.shift() : this.addTile();
      if (currentRow.length > 0 && currentRow[0].value === targetTile.value) {
        var tile1 = targetTile;
        targetTile = this.addTile(targetTile.value);
        tile1.mergedInto = targetTile;
        var tile2 = currentRow.shift();
        tile2.mergedInto = targetTile;
        targetTile.value += tile2.value;
      }
      resultRow[target] = targetTile;
      this.won = this.won || (targetTile.value === 2048);
      hasChanged = hasChanged || (targetTile.value !== this.cells[row][target].value);
    }
    this.cells[row] = resultRow;
  }
  return hasChanged;
};

Board.prototype.setPositions = function () {
  this.cells.forEach(function (row, rowIndex) {
    row.forEach(function (tile, columnIndex) {
      tile.oldRow = tile.row;
      tile.oldColumn = tile.column;
      tile.row = rowIndex;
      tile.column = columnIndex;
      tile.markForDeletion = false;
    });
  });
};

Board.fourProbability = 0.1;

Board.prototype.addRandomTile = function () {
  var emptyCells = [];
  for (var r = 0; r < Board.size; ++r) {
    for (var c = 0; c < Board.size; ++c) {
      if (this.cells[r][c].value === 0) {
        emptyCells.push({r: r, c: c});
      }
    }
  }
  var index = Math.floor(Math.random() * emptyCells.length);
  var cell = emptyCells[index];
  var newValue = Math.random() < Board.fourProbability ? 4 : 2;
  this.cells[cell.r][cell.c] = this.addTile(newValue);
};

Board.prototype.move = function (direction) {
  // 0 -> left, 1 -> up, 2 -> right, 3 -> down
  this.clearOldTiles();
  for (var i = 0; i < direction; ++i) {
    this.cells = rotateLeft(this.cells);
  }
  var hasChanged = this.moveLeft();
  for (var i = direction; i < 4; ++i) {
    this.cells = rotateLeft(this.cells);
  }
  if (hasChanged) {
    this.addRandomTile();
  }
  this.setPositions();
  return this;
};

Board.prototype.clearOldTiles = function () {
  this.tiles = this.tiles.filter(function (tile) { return tile.markForDeletion === false; });
  this.tiles.forEach(function (tile) { tile.markForDeletion = true; });
};

Board.prototype.hasWon = function () {
  return this.won;
};

Board.deltaX = [-1, 0, 1, 0];
Board.deltaY = [0, -1, 0, 1];

Board.prototype.hasLost = function () {
  var canMove = false;
  for (var row = 0; row < Board.size; ++row) {
    for (var column = 0; column < Board.size; ++column) {
      canMove = canMove || (this.cells[row][column].value === 0);
      for (var dir = 0; dir < 4; ++dir) {
        var newRow = row + Board.deltaX[dir];
        var newColumn = column + Board.deltaY[dir];
        if (newRow < 0 || newRow >= Board.size || newColumn < 0 || newColumn >= Board.size) {
          continue;
        }
        canMove = canMove || (this.cells[row][column].value === this.cells[newRow][newColumn].value);
      }
    }
  }
  return !canMove;
};

module.exports = Board;