import 'dart:html';
import 'package:vector_math/vector_math.dart';

class Demo {
  final CanvasElement _canvas;
  final Camera _camera;

  CanvasRenderingContext2D _context;

  Demo() : _canvas = document.createElement('canvas') as CanvasElement,
    _camera = new Camera(new Vector2(0.0, 0.0)) {
    _context = _canvas.getContext('2d') as CanvasRenderingContext2D;

    _canvas.width = 640;
    _canvas.height = 640;

    document.body.append(_canvas);
  }

  void start() {
    window.requestAnimationFrame(processTick);
  }

  void processTick(num delta) {
    update();
    render();
  }

  void update() {}

  void render() {
    var tileWidth = 32;
    var tileHeight = 32;

    for (var y = 0; y < 20; y++) {
      for (var x = 0; x < 20; x++) {
        var pos = new Vector2(x.toDouble(), y.toDouble());
        var relativePosition = _camera.getRelativePosition(pos);

        var colour = '#00ff00';
        if (((x + y) % 8) == 0)
          colour = '#ff00ff';
        else if (((x + y) % 4) == 0)
          colour = '#0000ff';
        else if (((x + y) % 2) == 0)
          colour = '#ff0000';

        _context.fillStyle = colour;
        _context.fillRect(x * tileWidth + relativePosition.x, y * tileHeight + relativePosition.y, tileWidth, tileHeight);
      }
    }
  }
}

class Camera {
  final Vector2 _position;

  Camera(this._position);

  Vector2 getRelativePosition(Vector2 position) {
    return new Vector2(position.x - _position.x, position.y - _position.y);
  }

  void moveTo(Vector2 position) {
    _position.x = position.x;
    _position.y = position.y;
  }

  void move(Vector2 position) {
    _position.x += position.x;
    _position.y += position.y;
  }
}