index.js

/**
 * Copyright 2016 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

// [START all]
/**
 * After a user has completed a purchase, send them a coupon via FCM valid on their next purchase.
 */
// [START trigger]
exports.sendCouponOnPurchase = functions.analytics.event('in_app_purchase').onLog((event) => {
// [END trigger]
  // [START attributes]
  const user = event.user;
  const uid = user.userId; // The user ID set via the setUserId API.
  const purchaseValue = event.valueInUSD; // Amount of the purchase in USD.
  const userLanguage = user.deviceInfo.userDefaultLanguage; // The user language in language-country format.
  // [END attributes]

  // For purchases above 500 USD, we send a coupon of higher value.
  if (purchaseValue > 500) {
    return sendHighValueCouponViaFCM(uid, userLanguage);
  }
  return sendCouponViaFCM(uid, userLanguage);
});
// [END all]

/**
 * Sends a coupon code via FCM to the given user.
 *
 * @param {string} uid The UID of the user.
 * @param {string} userLanguage The user language in language-country format.
 */
async function sendCouponViaFCM(uid, userLanguage) {
  // Fetching all the user's device tokens.
  const tokens = await getDeviceTokens(uid);
  if (tokens.length > 0) {
    // Notification details.
    let payload = {
      notification: {
        title: 'Thanks for your Purchase!',
        body: 'Get 10% off your next purchase with "COMEBACK10".',
      },
    };

    // Notification in French.
    if (userLanguage.split('-')[0] === 'fr') {
      payload = {
        notification: {
          title: 'Merci pour votre achat!',
          body: 'Obtenez 10% de réduction sur votre prochain achat avec "COMEBACK10".',
        },
      };
    }

    // Send notifications to all tokens.
    return admin.messaging().sendToDevice(tokens, payload);
  }
  return null;
}

/**
 * Sends a high value coupon vode via FCM to the given user.
 *
 * @param {string} uid The UID of the user.
 * @param {string} userLanguage The user language in language-country format.
 */
async function sendHighValueCouponViaFCM(uid, userLanguage) {
  // Fetching all the user's device tokens.
  const tokens = await getDeviceTokens(uid);
  if (tokens.length > 0) {
    // Notification details.
    let payload = {
      notification: {
        title: 'Thanks for your Purchase!',
        body: 'Get 30% off your next purchase with "COMEBACK30".',
      },
    };

    // Notification in French.
    if (userLanguage.split('-')[0] === 'fr') {
      payload = {
        notification: {
          title: 'Merci pour votre achat!',
          body: 'Obtenez 30% de réduction sur votre prochain achat avec "COMEBACK30".',
        },
      };
    }

    // Send notifications to all tokens.
    return admin.messaging().sendToDevice(tokens, payload);
  }
  return null;
}

/**
 * Get the Device Tokens for the given user.
 *
 * @param {string} uid The UID of the user.
 */
async function getDeviceTokens(uid) {
  const snap = await admin.database().ref(`/users/${uid}/tokens`).once('value');
  if (snap.exists()) {
    return Object.keys(snap.val());
  }
  return [];
}