slots.js

var Slots = (function(options) {
  this.mode = 'x';
  this.max = options.width;
  if (options.height) {
    this.mode = 'y';
    this.max = options.height;
  }
  this.grid = 0;
  this.items = [];
});

Slots.prototype = {
  shapeToArray: function(x, y) {
    if (this.mode == 'x') {
      if (x > this.max)
        throw 'x exceeds max width';
    } else {
      if (y > this.max)
        throw 'y exceeds max height';
      var _y = x;
      var _x = y;
      x = _x;
      y = _y;
    }

    var a = [];
    while (y-- > 0) {
      var m = this.max;
      var px = x;
      while (px-- > 0) {
        a.push(1);
        m--;
      }
      while (m-- > 0) {
        a.push(0);
      }
    }

    return a;

  },
  peek: function(x, y) {
    var shape = this.shapeToArray(x, y);
    var width = this.mode == 'x' ? x : y;
    var movement = this.max - width;
    var gridi = this.grid;
    var shapestr = shape.toString().replace(/,/g, '').match(/.*1/)[0];
    var slen = shapestr.length;
    var shapei = parseInt(shapestr, 2);

    var c = 0;
    while (true) {
      // var ok = ((grid ^ shape << q) & grid) == grid;
      for (var i = c; i <= movement + c; i++) {
        if (i + slen >= 32) {
          throw 'overflow, cannot fit shape';
        }
        var ok = ((gridi ^ shapei << i) & gridi) == gridi;
        if (ok) {
          var yi = (i / this.max)|0;
          var xi = (i % this.max);
          if (this.mode == 'x')
            return { x: xi, y: yi, i: i, shape: shapei };
          else
            return { x: yi, y: xi, i: i, shape: shapei };
        }
      }
      c += this.max;
    }
  },
  add: function(x, y) {
    var peek = this.peek(x, y);
    this.items.push(peek);
    this.grid = this.grid | (peek.shape << peek.i);
    return peek;
  }
};

if (typeof(module) != "undefined")
  module.exports = Slots;