src/services/events/event.model.js


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const cron = require('cron');
const Bluebird = require('bluebird');
const { model } = require('mongoose');
const schema = require('./event.schema.js');

const CronJob = cron.CronJob;

schema.methods.computeNextRunAt = function() {
  const job = new CronJob(this.schedule);
  const nextRunAt = job.nextDates();
  return new Date(nextRunAt);
};

schema.pre('save', function(next) {
  this.nextRunAt = this.computeNextRunAt();
  next();
});

schema.statics.rescheduleOldEvents = async function () {
  console.log('Reschedule old events');
  const oldEvents = await this.find({
    nextRunAt: {
      // TODO: skip single-fire events
      $lt: new Date()
    },
  });

  // Saving events triggers computing new nextRunAt
  return Bluebird.map(oldEvents, event => event.save());
};

schema.statics.findNextEvent = function () {
  return this.findOne(
    {
      nextRunAt: {
        $exists: 1,
        $gt: new Date()
      },
    },
    null,
    {
      sort: {
        nextRunAt: 1
      }
    }
  )
};

const Model = model('Event', schema);


module.exports = Model;