ขอหลักการทำระบบแบบ Task scheduler ตั้งเวลาแล้วให้ระบบทำงานเบื้องหลัง เอง

//import { auth, EventContext } from 'firebase-functions'
import * as functions from 'firebase-functions';
import { UserInfo } from '../../../common/models/userInfo';
import { UserRecord } from "firebase-functions/lib/providers/auth";
import moment from 'moment';
import { db } from "../config/config";

import * as admin from "firebase-admin";

async function _onProductsUpdated(change: any, context: any) {
  const productId = context.params.productId

  const newValue = change.after.data(); // e.g. {'displayName': 'FuckerMan', 'weight': 85}
  const oldValue = change.before.data();   // e.g. {'displayName': 'FuckerMan', 'weight': 65}

  var pv = 0.00;
  var mp = 0.00;
  var va = 0.00;
  var JiMi ="Very Big";

  if (newValue.unitCost != oldValue.unitCost) {
    const productCatgegory = db.collection("productCategory").where("productCatId", "==", newValue.productCatId)
                             .get()
                             .then( shapshot => {
                                const x = shapshot.docs[0].data();
                                 pv = x.productSellPrice.percentPlus;
                                 mp = x.productSellPrice.messengerPrice;
                                 va = x.productSellPrice.vat;
                             });

    const products = db.collection("products").where("productId", "==", productId)
      .get()
      .then(snapshot => {
        snapshot.forEach(doc => {
          // doc.ref.collection
          let rowUpdate = db.collection("products").doc(doc.id);
          let rowData = doc.data();
          let unitCost = rowData.unitCost; //unitCose
          let unitWeightFrom = rowData.productPackage.unitWeightFrom;
          let lastSellPrice = unitCost + ((unitCost * (pv / 100)) + (mp * unitWeightFrom)) * (1 + (va / 100));
          rowUpdate.update({ unitSellPrice: lastSellPrice })
        });
      });
  }
}

export const onProductsUpdated = functions.firestore
  .document("products/{productId}")
  .onUpdate(_onProductsUpdated);