(function(){
  'use strict';

  // Extend the element method
  Element.prototype.wordSearch = function(settings) {
    return new WordSearch(this, settings);
  }

  /**
   * Word seach
   *
   * @param {Element} wrapWl the game's wrap element
   * @param {Array} settings
   * constructor
   */
  function WordSearch(wrapEl, settings) {
    this.wrapEl = wrapEl;

    // Add `.ws-area` to wrap element
    this.wrapEl.classList.add('ws-area');

    // Default settings
    var default_settings = {
      'directions': ['W', 'N', 'WN', 'EN'],
      'gridSize': 10,
      'words': ['one', 'two', 'three', 'four', 'five'],
      'debug': false
    }
    this.settings = Object.merge(settings, default_settings);

    // Check the words' length if it is overflow the grid
    if (this.parseWords(this.settings.gridSize)) {
      // Add words into the matrix data
      var isWorked = false;

      while (isWorked == false) {
        // initialize the application
        this.initialize();

        isWorked = this.addWords();
      }

      // Fill up the remaining blank items
      if (!this.settings.debug) {
        this.fillUpFools();
      }

      // Draw the matrix into wrap element
      this.drawmatrix();
    }
  }

  /**
   * Parse words
   * @param {Number} Max size
   * @return {Boolean}
   */
  WordSearch.prototype.parseWords = function(maxSize) {
    var itWorked = true;

    for (var i = 0; i < this.settings.words.length; i++) {
      // Convert all the letters to upper case
      this.settings.words[i] = this.settings.words[i].toUpperCase();

      var word = this.settings.words[i];
      if (word.length > maxSize) {
        alert('The length of word `' + word + '` is overflow the gridSize.');
        console.error('The length of word `' + word + '` is overflow the gridSize.');
        itWorked = false;
      }
    }

    return itWorked;
  }

  /**
   * Put the words into the matrix
   */
  WordSearch.prototype.addWords = function() {
      var keepGoing = true,
        counter = 0,
        isWorked = true;

      while (keepGoing) {
        // Getting random direction
        var dir = this.settings.directions[Math.rangeInt(this.settings.directions.length - 1)],
          result = this.addWord(this.settings.words[counter], dir),
          isWorked = true;

        if (result == false) {
          keepGoing = false;
          isWorked = false;
        }

        counter++;
        if (counter >= this.settings.words.length) {
          keepGoing = false;
        }
      }

      return isWorked;
  }

  /**
   * Add word into the matrix
   *
   * @param {String} word
   * @param {Number} direction
   */
  WordSearch.prototype.addWord = function(word, direction) {
    var itWorked = true,
      directions = {
        'W': [0, 1], // Horizontal (From left to right)
        'N': [1, 0], // Vertical (From top to bottom)
        'WN': [1, 1], // From top left to bottom right
        'EN': [1, -1] // From top right to bottom left
      },
      row, col; // y, x

    switch (direction) {
      case 'W': // Horizontal (From left to right)
        var row = Math.rangeInt(this.settings.gridSize  - 1),
          col = Math.rangeInt(this.settings.gridSize - word.length);
        break;

      case 'N': // Vertical (From top to bottom)
        var row = Math.rangeInt(this.settings.gridSize - word.length),
          col = Math.rangeInt(this.settings.gridSize  - 1);
        break;

      case 'WN': // From top left to bottom right
        var row = Math.rangeInt(this.settings.gridSize - word.length),
          col = Math.rangeInt(this.settings.gridSize - word.length);
        break;

      case 'EN': // From top right to bottom left
        var row = Math.rangeInt(this.settings.gridSize - word.length),
          col = Math.rangeInt(word.length - 1, this.settings.gridSize - 1);
        break;

      default:
        var error = 'UNKNOWN DIRECTION ' + direction + '!';
        alert(error);
        console.log(error);
        break;
    }

    // Add words to the matrix
    for (var i = 0; i < word.length; i++) {
      var newRow = row + i * directions[direction][0],
        newCol = col + i * directions[direction][1];

      // The letter on the board
      var origin = this.matrix[newRow][newCol].letter;

      if (origin == '.' || origin == word[i]) {
        this.matrix[newRow][newCol].letter = word[i];
      } else {
        itWorked = false;
      }
    }

    return itWorked;
  }

  /**
   * Initialize the application
   */
  WordSearch.prototype.initialize = function() {
    /**
     * Letter matrix
     *
     * param {Array}
     */
    this.matrix = [];

    /**
     * Selection from
     * @Param {Object}
     */
    this.selectFrom = null;

    /**
     * Selected items
     */
    this.selected = [];

    this.initmatrix(this.settings.gridSize);
  }

  /**
   * Fill default items into the matrix
   * @param {Number} size Grid size
   */
  WordSearch.prototype.initmatrix = function(size) {
    for (var row = 0; row < size; row++) {
      for (var col = 0; col < size; col++) {
        var item = {
          letter: '.', // Default value
          row: row,
          col: col
        }

        if (!this.matrix[row]) {
          this.matrix[row] = [];
        }

        this.matrix[row][col] = item;
      }
    }
  }

  /**
   * Draw the matrix
   */
  WordSearch.prototype.drawmatrix = function() {
    for (var row = 0; row < this.settings.gridSize; row++) {
      // New row
      var divEl = document.createElement('div');
      divEl.setAttribute('class', 'ws-row');
      this.wrapEl.appendChild(divEl);

      for (var col = 0; col < this.settings.gridSize; col++) {
        var cvEl = document.createElement('canvas');
        cvEl.setAttribute('class', 'ws-col');
        cvEl.setAttribute('width', 40);
        cvEl.setAttribute('height', 40);

        // Fill text in middle center
        var x = cvEl.width / 2,
          y = cvEl.height / 2;

        var ctx = cvEl.getContext('2d');
        ctx.font = '400 28px Calibri';
        ctx.textAlign = 'center';
        ctx.textBaseline = 'middle';
        ctx.fillStyle = '#333'; // Text color
        ctx.fillText(this.matrix[row][col].letter, x, y);

        // Add event listeners
        cvEl.addEventListener('mousedown', this.onMousedown(this.matrix[row][col]));
        cvEl.addEventListener('mouseover', this.onMouseover(this.matrix[row][col]));
        cvEl.addEventListener('mouseup', this.onMouseup());

        divEl.appendChild(cvEl);
      }
    }
  }

  /**
   * Fill up the remaining items
   */
  WordSearch.prototype.fillUpFools = function() {
    for (var row = 0; row < this.settings.gridSize; row++) {
      for (var col = 0; col < this.settings.gridSize; col++) {
        if (this.matrix[row][col].letter == '.') {
          // Math.rangeInt(65, 90) => A ~ Z
          this.matrix[row][col].letter = String.fromCharCode(Math.rangeInt(65, 90));
        }
      }
    }
  }

  /**
   * Returns matrix items
   * @param rowFrom
   * @param colFrom
   * @param rowTo
   * @param colTo
   * @return {Array}
   */
  WordSearch.prototype.getItems = function(rowFrom, colFrom, rowTo, colTo) {
    var items = [];

    if ( rowFrom === rowTo || colFrom === colTo || Math.abs(rowTo - rowFrom) == Math.abs(colTo - colFrom) ) {
      var shiftY = (rowFrom === rowTo) ? 0 : (rowTo > rowFrom) ? 1 : -1,
        shiftX = (colFrom === colTo) ? 0 : (colTo > colFrom) ? 1 : -1,
        row = rowFrom,
        col = colFrom;

      items.push(this.getItem(row, col));
      do {
        row += shiftY;
        col += shiftX;
        items.push(this.getItem(row, col));
      } while( row !== rowTo || col !== colTo );
    }

    return items;
  }

  /**
   * Returns matrix item
   * @param {Number} row
   * @param {Number} col
   * @return {*}
   */
  WordSearch.prototype.getItem = function(row, col) {
    return (this.matrix[row] ? this.matrix[row][col] : undefined);
  }

  /**
   * Clear the exist highlights
   */
  WordSearch.prototype.clearHighlight = function() {
    var selectedEls = document.querySelectorAll('.ws-selected');
    for (var i = 0; i < selectedEls.length; i++) {
      selectedEls[i].classList.remove('ws-selected');
    }
  }

  /**
   * Lookup if the wordlist contains the selected
   * @param {Array} selected
   */
  WordSearch.prototype.lookup = function(selected) {
    var words = [''];

    for (var i = 0; i < selected.length; i++) {
      words[0] += selected[i].letter;
    }
    words.push(words[0].split('').reverse().join(''));

    if (this.settings.words.indexOf(words[0]) > -1 ||
        this.settings.words.indexOf(words[1]) > -1) {
      for (var i = 0; i < selected.length; i++) {
        var row = selected[i].row + 1,
          col = selected[i].col + 1,
          el = document.querySelector('.ws-area .ws-row:nth-child(' + row + ') .ws-col:nth-child(' + col + ')');

        el.classList.add('ws-found');
      }
    }
  }

  /**
   * Mouse event - Mouse down
   * @param {Object} item
   */
  WordSearch.prototype.onMousedown = function(item) {
    var _this = this;
    return function() {
      _this.selectFrom = item;
    }
  }

  /**
   * Mouse event - Mouse move
   * @param {Object}
   */
  WordSearch.prototype.onMouseover = function(item) {
    var _this = this;
    return function() {
      if (_this.selectFrom) {
        _this.selected = _this.getItems(_this.selectFrom.row, _this.selectFrom.col, item.row, item.col);

        _this.clearHighlight();

        for (var i = 0; i < _this.selected.length; i ++) {
          var current = _this.selected[i],
            row = current.row + 1,
            col = current.col + 1,
            el = document.querySelector('.ws-area .ws-row:nth-child(' + row + ') .ws-col:nth-child(' + col + ')');

          el.className += ' ws-selected';
        }
      }
    }
  }

  /**
   * Mouse event - Mouse up
   */
  WordSearch.prototype.onMouseup = function() {
    var _this = this;
    return function() {
      _this.selectFrom = null;
      _this.clearHighlight();
      _this.lookup(_this.selected);
      _this.selected = [];
    }
  }

})();