feat: use cron to schedule jobs

1 files changed, 55 insertions, 0 deletions

diff --git a/src/services/events/event.model.js b/src/services/events/event.model.js
new file mode 100644
index 0000000..ef86572
--- /dev/null
+++ b/src/services/events/event.model.js
@@ -0,0 +1,55 @@
+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;
+
+
+