import { loadImageAsync, noop } from './util';

// el: {
//     state,
//     src,
//     error,
//     loading
// }

export default class ReactiveListener {
  constructor({
    el,
    src,
    error,
    loading,
    bindType,
    $parent,
    options,
    cors,
    elRenderer,
    imageCache,
  }) {
    this.el = el;
    this.src = src;
    this.error = error;
    this.loading = loading;
    this.bindType = bindType;
    this.attempt = 0;
    this.cors = cors;

    this.naturalHeight = 0;
    this.naturalWidth = 0;

    this.options = options;

    this.rect = null;

    this.$parent = $parent;
    this.elRenderer = elRenderer;
    this._imageCache = imageCache;
    this.performanceData = {
      init: Date.now(),
      loadStart: 0,
      loadEnd: 0,
    };

    this.filter();
    this.initState();
    this.render('loading', false);
  }

  /*
   * init listener state
   * @return
   */
  initState() {
    if ('dataset' in this.el) {
      this.el.dataset.src = this.src;
    } else {
      this.el.setAttribute('data-src', this.src);
    }

    this.state = {
      loading: false,
      error: false,
      loaded: false,
      rendered: false,
    };
  }

  /*
   * record performance
   * @return
   */
  record(event) {
    this.performanceData[event] = Date.now();
  }

  /*
   * update image listener data
   * @param  {String} image uri
   * @param  {String} loading image uri
   * @param  {String} error image uri
   * @return
   */
  update({ src, loading, error }) {
    const oldSrc = this.src;
    this.src = src;
    this.loading = loading;
    this.error = error;
    this.filter();
    if (oldSrc !== this.src) {
      this.attempt = 0;
      this.initState();
    }
  }

  /*
   * get el node rect
   * @return
   */
  getRect() {
    this.rect = this.el.getBoundingClientRect();
  }

  /*
   *  check el is in view
   * @return {Boolean} el is in view
   */
  checkInView() {
    this.getRect();
    return (
      this.rect.top < window.innerHeight * this.options.preLoad &&
      this.rect.bottom > this.options.preLoadTop &&
      this.rect.left < window.innerWidth * this.options.preLoad &&
      this.rect.right > 0
    );
  }

  /*
   * listener filter
   */
  filter() {
    Object.keys(this.options.filter).forEach((key) => {
      this.options.filter[key](this, this.options);
    });
  }

  /*
   * render loading first
   * @params cb:Function
   * @return
   */
  renderLoading(cb) {
    this.state.loading = true;
    loadImageAsync(
      {
        src: this.loading,
        cors: this.cors,
      },
      () => {
        this.render('loading', false);
        this.state.loading = false;
        cb();
      },
      () => {
        // handler `loading image` load failed
        cb();
        this.state.loading = false;
        if (!this.options.silent)
          console.warn(
            `VueLazyload log: load failed with loading image(${this.loading})`
          );
      }
    );
  }

  /*
   * try load image and  render it
   * @return
   */
  load(onFinish = noop) {
    if (this.attempt > this.options.attempt - 1 && this.state.error) {
      if (!this.options.silent)
        console.log(
          `VueLazyload log: ${this.src} tried too more than ${this.options.attempt} times`
        );
      onFinish();
      return;
    }
    if (this.state.rendered && this.state.loaded) return;
    if (this._imageCache.has(this.src)) {
      this.state.loaded = true;
      this.render('loaded', true);
      this.state.rendered = true;
      return onFinish();
    }

    this.renderLoading(() => {
      this.attempt++;

      this.options.adapter.beforeLoad?.(this, this.options);
      this.record('loadStart');

      loadImageAsync(
        {
          src: this.src,
          cors: this.cors,
        },
        (data) => {
          this.naturalHeight = data.naturalHeight;
          this.naturalWidth = data.naturalWidth;
          this.state.loaded = true;
          this.state.error = false;
          this.record('loadEnd');
          this.render('loaded', false);
          this.state.rendered = true;
          this._imageCache.add(this.src);
          onFinish();
        },
        (err) => {
          !this.options.silent && console.error(err);
          this.state.error = true;
          this.state.loaded = false;
          this.render('error', false);
        }
      );
    });
  }

  /*
   * render image
   * @param  {String} state to render // ['loading', 'src', 'error']
   * @param  {String} is form cache
   * @return
   */
  render(state, cache) {
    this.elRenderer(this, state, cache);
  }

  /*
   * output performance data
   * @return {Object} performance data
   */
  performance() {
    let state = 'loading';
    let time = 0;

    if (this.state.loaded) {
      state = 'loaded';
      time =
        (this.performanceData.loadEnd - this.performanceData.loadStart) / 1000;
    }

    if (this.state.error) state = 'error';

    return {
      src: this.src,
      state,
      time,
    };
  }

  /*
   * $destroy
   * @return
   */
  $destroy() {
    this.el = null;
    this.src = null;
    this.error = null;
    this.loading = null;
    this.bindType = null;
    this.attempt = 0;
  }
}
