class Screen {
  CanvasElement _canvas;
  CanvasRenderingContext2D _context;
  List<Drawable> _objects = new List<Drawable>();
  int _timeoflastfpscount = 0, _frameCount = 0, _prevInfo = 0,  _sizeX, _sizeY, previousTime = new Date.now().millisecondsSinceEpoch;
  bool _fullscreen = false, _schResize = false;
  Random rng = new Random();
  Screen.create (CanvasElement this._canvas, int this._sizeX, int this._sizeY, bool this._fullscreen) {
    if (_fullscreen) {
      _sizeX = window.innerWidth;
      _sizeY = window.innerHeight;
      window.on.resize.add((event) {
        _sizeX = window.innerWidth;
        _sizeY = window.innerHeight;
        _schResize = true;
      });
    }
    //Initialise the Canvas
    _canvas.height = _sizeY;
    _canvas.width = _sizeX;
    _context = _canvas.context2d;
  }
  int getAppWidth () {
    return _sizeX;
  }
  int getAppHeight () {
    return _sizeY;
  }
  void updateFPS (int time, CanvasRenderingContext2D ctx) {
    _frameCount++;
    int sinceLast = (time - _timeoflastfpscount);
    if (sinceLast >= 1000) {
     _prevInfo = ((_frameCount / sinceLast) * 1000).round().toInt();
     _frameCount = 0;
     _timeoflastfpscount = time;
    }
    ctx.font = "12px 'Open Sans'";
    ctx.fillStyle = "red";
    ctx.fillText("${_prevInfo.toString()} FPS - Frames drawn since last: ${_frameCount}", 0, 16, this._sizeX);
 }

  void clear(CanvasRenderingContext2D ctx) {
    ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
  }

  void spawn (Drawable d) {
    _objects.addLast(d);
  }
  void updateObjs (List<Drawable> obj, double secondsSinceLastFrame) {
    if (!obj.isEmpty()) {
      int i = 0;
      obj.forEach((Drawable d) {
        if (d.needsUpdate) { d.update(secondsSinceLastFrame); }
        if (d.markDead) {
          obj.removeAt(i);
          i--;
        }
        i++;
      });
    }
  }
  void draw (List<Drawable> obj, CanvasRenderingContext2D ctx) {
    if (!obj.isEmpty()) {
      obj.forEach((Drawable d) {
        d.draw(ctx);
      });
    }
  }
  void update (int time) {
    if (time == null) {
      time = new Date.now().millisecondsSinceEpoch;
    }
    //Draw the frame
    if (!_schResize) clear(_context);
    else {
      _canvas.height = _sizeY;
      _canvas.width = _sizeX;
    }
    updateObjs(_objects, ((time - previousTime).toDouble() / 1000));
    draw(_objects, _context);
    //Show our FPS on the canvas passing along the time at the begining
    updateFPS(time, _context);
    //Request the next frame!
    previousTime = time;
  }
}