spritejs/spritejs

/* globals GameGlobal, wx */
export function polyfill({ENV}) {
  const firstCanvas = wx.createCanvas();
  let getFirstCanvas = false;

  const {width, height} = firstCanvas;

  ENV.createCanvas = function () {
    if(!getFirstCanvas) {
      getFirstCanvas = true;
      return firstCanvas;
    }
    const canvas = wx.createCanvas();
    canvas._offscreen = true;
    return canvas;
  };

  GameGlobal.Image = function () {
    return wx.createImage();
  };

  function wrap(type, event) {
    event.type = type;
    event.target = {
      getBoundingClientRect() {
        return {
          top: 0,
          left: 0,
          width,
          height,
        };
      },
      width,
      height,
    };
    return event;
  }

  class Container {
    constructor() {
      this.children = [];
    }

    get clientWidth() {
      return width;
    }

    get clientHeight() {
      return height;
    }

    addEventListener(type, listener) {
      if(type === 'touchstart') {
        wx.onTouchStart((e) => {
          listener(wrap('touchstart', e));
        });
      }
      if(type === 'touchmove') {
        wx.onTouchMove((e) => {
          listener(wrap('touchmove', e));
        });
      }
      if(type === 'touchend') {
        wx.onTouchEnd((e) => {
          listener(wrap('touchend', e));
        });
      }
      if(type === 'touchcancel') {
        wx.onTouchCancel((e) => {
          listener(wrap('touchcancel', e));
        });
      }
    }

    appendChild(el) {
      this.children.push(el);
    }

    removeChild(el) {
      const idx = this.children.indexOf(el);
      if(idx >= 0) {
        this.children.splice(idx, 1);
        return el;
      }
      return null;
    }

    insertBefore(el, ref) {
      if(ref == null) return this.appendChild(el);
      const idx = this.children.indexOf(ref);
      if(idx >= 0) {
        this.children.splice(idx, 0, el);
      }
      return null;
    }

    replaceChild(el, ref) {
      const idx = this.children.indexOf(ref);
      if(idx >= 0) {
        this.children.splice(idx, 1, el);
        return el;
      }
      return null;
    }
  }

  ENV.Container = Container;
}