(function(exports) {
  var angle = Math.PI / 6;

  var identity = [
    1, 0, 0, 0,
    0, 1, 0, 0,
    0, 0, 1, 0
  ];

  function Isometric(context) {
    this._moveTo = context.moveTo.bind(context);
    this._lineTo = context.lineTo.bind(context);
    this.closePath = context.closePath.bind(context);
    this._matrix = identity.slice();
    this._matrixes = [];
    this._projection = [
      Math.cos(angle), Math.cos(Math.PI - angle),
      -Math.sin(angle), -Math.sin(Math.PI - angle)
    ];
  }

  Isometric.prototype = {
    _project: function(point, x, y, z) {
      point(
        x * this._projection[0] + y * this._projection[1],
        x * this._projection[2] + y * this._projection[3] - z
      );
    },
    _transform: function(point, x, y, z) {
      this._project(point,
        x * this._matrix[0] + y * this._matrix[1] + z * this._matrix[2] + this._matrix[3],
        x * this._matrix[4] + y * this._matrix[5] + z * this._matrix[6] + this._matrix[7],
        x * this._matrix[8] + y * this._matrix[9] + z * this._matrix[10] + this._matrix[11]
      );
    },
    save: function() {
      this._matrixes.push(this._matrix.slice());
    },
    restore: function() {
      if (this._matrixes.length) this._matrix = this._matrixes.pop();
    },

    // | a b c d |   | kx  0  0 0 |   | a * kx b * ky c * kz d |
    // | e f g h | * |  0 ky  0 0 | = | e * kx f * ky g * kz h |
    // | i j k l |   |  0  0 kz 0 |   | i * kx j * ky k * kz l |
    // | 0 0 0 1 |   |  0  0  0 1 |   |      0      0      0 1 |
    scale3d: function(kx, ky, kz) {
      this._matrix[0] *= kx;
      this._matrix[1] *= ky;
      this._matrix[2] *= kz;
      this._matrix[4] *= kx;
      this._matrix[5] *= ky;
      this._matrix[6] *= kz;
      this._matrix[8] *= kx;
      this._matrix[9] *= ky;
      this._matrix[10] *= kz;
    },

    // | a b c d |   | cos -sin 0 0 |   | a * cos + b * sin a * -sin + b * cos c d |
    // | e f g h | * | sin  cos 0 0 | = | e * cos + f * sin e * -sin + f * cos g h |
    // | i j k l |   |   0    0 1 0 |   | i * cos + j * sin i * -sin + j * cos k l |
    // | 0 0 0 1 |   |   0    0 0 1 |   |                 0                  0 0 1 |
    rotateZ: function(angle) {
      var cos = Math.cos(angle),
          sin = Math.sin(angle),
          a = this._matrix[0],
          b = this._matrix[1],
          c = this._matrix[2],
          d = this._matrix[3],
          e = this._matrix[4],
          f = this._matrix[5],
          g = this._matrix[6],
          h = this._matrix[7],
          i = this._matrix[8],
          j = this._matrix[9],
          k = this._matrix[10],
          l = this._matrix[11];
      this._matrix[0] = a * cos + b * sin;
      this._matrix[1] = a * -sin + b * cos;
      this._matrix[4] = e * cos + f * sin;
      this._matrix[5] = e * -sin + f * cos;
      this._matrix[8] = i * cos + j * sin;
      this._matrix[9] = i * -sin + j * cos;
    },

    // | a b c d |   | 1 0 0 tx |   | a b c a * tx + b * ty + c * tz + d |
    // | e f g h | * | 0 1 0 ty | = | e f g e * tx + f * ty + g * tz + h |
    // | i j k l |   | 0 0 1 tz |   | i j k i * tx + j * ty + k * tz + l |
    // | 0 0 0 1 |   | 0 0 0  1 |   | 0 0 0                            1 |
    translate3d: function(tx, ty, tz) {
      this._matrix[3] += this._matrix[0] * tx + this._matrix[1] * ty + this._matrix[2] * tz;
      this._matrix[7] += this._matrix[4] * tx + this._matrix[5] * ty + this._matrix[6] * tz;
      this._matrix[11] += this._matrix[8] * tx + this._matrix[9] * ty + this._matrix[10] * tz;
    },

    moveTo: function(x, y, z) {
      this._transform(this._moveTo, x, y, z);
    },
    lineTo: function(x, y, z) {
      this._transform(this._lineTo, x, y, z);
    }
  };

  exports.isometric = function(context) {
    return new Isometric(context);
  };

})(this);