const { Types } = require('mongoose');
const { Service } = require('feathers-mongoose');
const _ = require('lodash');
const cron = require('cron');
const Bluebird = require('bluebird');

const Model = require('./event.model.js');
const handleAttendClassJob = require('../../handlers');
const CronJob = cron.CronJob;

const handleTestJob = () => new Promise(res => setTimeout(res, 10000));


class Events extends Service {
  async setup(app, path) {
    this.jobs = [];
    await this.rescheduleMissedEvents();

    const job = new CronJob('*/10 * * * * *', () => this.updateJobs());
    job.start();
  }

  startAllJobs() {
    this.jobs.forEach(job => job.start());
  }

  stopAllJobs() {
    this.jobs.forEach(job => job.stop());
  }

  async rescheduleMissedEvents() {
    const missedEvents = await this.Model.findMissedEvents();
    return Bluebird.map(missedEvents, event => event.save());
  }

  async updateJobs() {
    // Reschedule missed events before we stop jobs to avoid
    // accidentally stopping the job that has not triggered yet
    // (if event schedule resonates with updateJobs schedule)
    await this.rescheduleMissedEvents();

    this.stopAllJobs();

    const events = await this.Model.findNextEvents();
    if (!events.length) console.log('WARNING: no upcoming events');
    this.jobs = events.map(event => new CronJob(
      event.schedule,
      () => this.run(event._id)
    ));

    this.startAllJobs();
  }

  async run(id) {
    const event = await this.Model.findById(id);

    try {
      event.start();
      await handleAttendClassJob(event);
      return event.complete();
    } catch (error) {
      event.fail(error);
    }
  }
}


module.exports = app => {
  app.use('/events', new Events({ Model }));
};