import _ from 'lodash';
import compareDesc from 'date-fns/compare_desc';
import debug from 'debug';

import { getMediumFeed } from './medium';
import { getLybsynFeed } from './lybsyn';

const log = debug('fcc:rss:news-feed');

const fiveMinutes = 1000 * 60 * 5;

class NewsFeed {
  constructor() {
    this.state = {
      readyState: false,
      mediumFeed: [],
      lybsynFeed: [],
      combinedFeed: []
    };
    this.refreshFeeds();

    setInterval(this.refreshFeeds, fiveMinutes);
  }

  setState = stateUpdater => {
    const newState = stateUpdater(this.state);
    this.state = _.merge({}, this.state, newState);
    return;
  };

  refreshFeeds = () => {
    const currentFeed = this.state.combinedFeed.slice(0);
    log('grabbing feeds');
    return Promise.all([getMediumFeed(), getLybsynFeed()])
      .then(([mediumFeed, lybsynFeed]) =>
        this.setState(state => ({
          ...state,
          mediumFeed,
          lybsynFeed
        }))
      )
      .then(() => {
        log('crossing the streams');
        const { mediumFeed, lybsynFeed } = this.state;
        const combinedFeed = [...mediumFeed, ...lybsynFeed].sort((a, b) => {
          return compareDesc(a.isoDate, b.isoDate);
        });
        this.setState(state => ({
          ...state,
          combinedFeed,
          readyState: true
        }));
      })
      .catch(err => {
        console.log(err);
        this.setState(state => ({
          ...state,
          combinedFeed: currentFeed
        }));
      });
  };

  getFeed = () =>
    new Promise(resolve => {
      let notReadyCount = 0;

      function waitForReady() {
        log('notReadyCount', notReadyCount);
        notReadyCount++;
        return this.state.readyState || notReadyCount === 5
          ? resolve(this.state.combinedFeed)
          : setTimeout(waitForReady, 100);
      }
      log('are we ready?', this.state.readyState);
      return this.state.readyState
        ? resolve(this.state.combinedFeed)
        : setTimeout(waitForReady, 100);
    });
}

export default NewsFeed;