exports.listenForCoupons = functions.database.ref('/couponsRequests')
  .onWrite(event => {
    const dbRef = event.data.ref;
    const delta = event['data']['_delta'];

    console.log('Delta from coupons', delta);

    Object
      .keys(delta)
      .forEach(row => {
        if(typeof delta[row] !== 'string')
          return;

        const promisify = whereToGo => dbRef.parent
          .child(`/${whereToGo}`)
          .orderByChild('discountCode')
          .startAt(delta[row])
          .endAt(delta[row])
          .once('value');

        const promise1 = promisify('private_coupons');
        const promise2 = promisify('public_coupons');

        Promise.all([promise1, promise2])
          .then(arr => {
            arr.forEach(snap => {
              if(snap.val()) {
                let couponObject = snap.val();
                console.log("Coupon object", couponObject);
                dbRef.parent
                  .child(`couponsRequests/${row}`)
                  .set(couponObject[Object.keys(couponObject)[0]]);
              }
            })
          });
      });
  });