firebase_cloud_function_push_message_with_different_timezone.js

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

exports.sendPushMessages = functions.pubsub
  .schedule("every 1 hours")
  .onRun(async (context) => {
    // Retrieve all users from Firestore collection
    const usersRef = admin.firestore().collection("users");
    const usersSnapshot = await usersRef.get();
    const users = usersSnapshot.docs.map((doc) => doc.data());

    // Loop through each user
    for (const user of users) {
      // Get current date and time in user's timezone
      const date = new Date().toLocaleString("en-US", {
        timeZone: user.timezone,
      });
      const hour = parseInt(date.split(",")[1].split(":")[0]);
      const minute = parseInt(date.split(",")[1].split(":")[1]);
      const day = date.split(",")[0];

      // Determine message text based on user's preferred language and current day of the week
      let messageText;
      if (user.language === "ko") {
        switch (day) {
          case "Monday":
            messageText = "월요일에만 나타나는 메시지입니다!";
            break;
          case "Tuesday":
            messageText = "화요일에만 나타나는 메시지입니다!";
            break;
          case "Wednesday":
            messageText = "수요일에만 나타나는 메시지입니다!";
            break;
          case "Thursday":
            messageText = "목요일에만 나타나는 메시지입니다!";
            break;
          case "Friday":
            messageText = "금요일에만 나타나는 메시지입니다!";
            break;
          case "Saturday":
            messageText = "토요일에만 나타나는 메시지입니다!";
            break;
          case "Sunday":
            messageText = "일요일에만 나타나는 메시지입니다!";
            break;
          default:
            messageText = "이는 매 시간마다 발송되는 일반적인 알림입니다.";
            break;
        }
      } else {
        switch (day) {
          case "Monday":
            messageText = "This is a message that only appears on Mondays!";
            break;
          case "Tuesday":
            messageText = "This is a message that only appears on Tuesdays!";
            break;
          case "Wednesday":
            messageText = "This is a message that only appears on Wednesdays!";
            break;
          case "Thursday":
            messageText = "This is a message that only appears on Thursdays!";
            break;
          case "Friday":
            messageText = "This is a message that only appears on Fridays!";
            break;
          case "Saturday":
            messageText = "This is a message that only appears on Saturdays!";
            break;
          case "Sunday":
            messageText = "This is a message that only appears on Sundays!";
            break;
          default:
            messageText = "This is a general reminder that is sent every hour.";
            break;
        }
      }

      // Check if it's time to send a notification (11 PM local time)
      if (hour === 23) {
        const message = {
          notification: {
            title: "Hourly Reminder",
            body: messageText,
          },
        };
        // Send message to user's FCM token
        const response = await admin
          .messaging()
          .sendToDevice(user.fcmToken, message);
        console.log(`Message sent to ${user.timezone}:`, response);
      }
    }
  });