const { NoNewListingsError } = require('./errors');
const { setKnownListings, getKnownListings } = require('./services/storage/listingsStorage');

const notify = require('./notification/notify');
const xray = require('./services/scraper');

class FredyRuntime {
  /**
   *
   * @param providerConfig the config for the specific provider, we're going to query at the moment
   * @param notificationConfig the config for all notifications
   * @param providerId the id of the provider currently in use
   * @param jobKey key of the job that is currently running (from within the config)
   */
  constructor(providerConfig, notificationConfig, providerId, jobKey) {
    this._providerConfig = providerConfig;
    this._notificationConfig = notificationConfig;
    this._providerId = providerId;
    this._jobKey = jobKey;
  }

  execute() {
    return (
      Promise.resolve(this._providerConfig.url)
        //scraping the site and try finding new listings
        .then(this._getListings.bind(this))
        //bring them in a proper form (dictated by the provider)
        .then(this._normalize.bind(this))
        //filter listings with stuff tagged by the blacklist of the provider
        .then(this._filter.bind(this))
        //check if new listings available. if so proceed
        .then(this._findNew.bind(this))
        //store everything in db
        .then(this._save.bind(this))
        //notify the user using the configured notification adapter
        .then(this._notify.bind(this))
        //if an error occurred on the way, handle it here.
        .catch(this._handleError.bind(this))
    );
  }

  _getListings(url) {
    return new Promise((resolve, reject) => {
      let x = xray(url, this._providerConfig.crawlContainer, [this._providerConfig.crawlFields]);

      x((err, listings) => {
        if (err) {
          reject(err);
        } else {
          resolve(listings);
        }
      });
    });
  }

  _normalize(listings) {
    return listings.map(this._providerConfig.normalize);
  }

  _filter(listings) {
    return listings.filter(this._providerConfig.filter);
  }

  _findNew(listings) {
    const newListings = listings.filter((o) => getKnownListings(this._jobKey, this._providerId)[o.id] == null);

    if (newListings.length === 0) {
      throw new NoNewListingsError();
    }

    return newListings;
  }

  _notify(newListings) {
    const sendNotifications = notify.send(this._providerId, newListings, this._notificationConfig, this._jobKey);
    return Promise.all(sendNotifications).then(() => newListings);
  }

  _save(newListings) {
    const currentListings = getKnownListings(this._jobKey, this._providerId) || {};
    newListings.forEach((listing) => {
      currentListings[listing.id] = Date.now();
    });
    setKnownListings(this._jobKey, this._providerId, currentListings);
    return newListings;
  }

  _handleError(err) {
    if (err.name !== 'NoNewListingsError') console.error(err);
  }
}

module.exports = FredyRuntime;