S.Drawing = (function () {
  var canvas,
      context,
      renderFn,
      requestFrame = window.requestAnimationFrame       ||
                     window.webkitRequestAnimationFrame ||
                     window.mozRequestAnimationFrame    ||
                     window.oRequestAnimationFrame      ||
                     window.msRequestAnimationFrame     ||
                     function (callback) {
                        window.setTimeout(callback, 1000 / 60);
                      };

  return {
    init: function (el) {
      canvas = document.querySelector(el);
      context = canvas.getContext('2d');
      this.adjustCanvas();

      window.addEventListener('resize', function () {
        S.Drawing.adjustCanvas();
      });
    },

    loop: function (fn) {
      renderFn = !renderFn ? fn : renderFn;
      this.clearFrame();
      renderFn();
      requestFrame.call(window, this.loop.bind(this));
    },

    adjustCanvas: function () {
      canvas.width = window.innerWidth;
      canvas.height = window.innerHeight;
    },

    clearFrame: function () {
      context.clearRect(0, 0, canvas.width, canvas.height);
    },

    getArea: function () {
      return { w: canvas.width, h: canvas.height };
    },

    drawCircle: function (p, c) {
      context.fillStyle = c.render();
      context.beginPath();
      context.arc(p.x, p.y, p.z, 0, 2 * Math.PI, true);
      context.closePath();
      context.fill();
    }
  };
}());