Function

'use strict'

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

exports.sendNotification = functions.database.ref('/Notifications/{user_id}/{notification_id}').onWrite(event => {

    const user_id = event.params.user_id;
    const notification_id = event.params.notification_id;

    console.log('User ID is : ', user_id);
    console.log('Notification ID is : ', notification_id);

    if(!event.data.val()) {
        return console.log('A Notification has been deleted from database. Sender : ', notification_id);
    }

    const fromUser = admin.database().ref(`/Notifications/${user_id}/${notification_id}`).once('value');
    return fromUser.then(fromUserResult => {

        const from_user_id = fromUserResult.val().from;

        console.log("You have a new request from : ", from_user_id);

        const userQuery = admin.database().ref(`/Users/${from_user_id}/name`).once('value');
        return userQuery.then(userResult => {

            const userName = userResult.val();

            const deviceToken = admin.database().ref(`/Users/${user_id}/device_token`).once('value');
            return deviceToken.then(result => {

                const token_id = result.val();
                console.log('Token ID is : ', token_id);

                const payload = {
                    notification: {
                        title: "New Friend Request",
                        body: `${userName} has sent you Friend Request`,
                        icon: "default",
                        click_action: "com.bertho.chat_TARGET_NOTIFICATION"
                    },
                    data: {
                        from_user_id: from_user_id
                    }
                };

                console.log('SENT FROM : ', from_user_id);

                return admin.messaging().sendToDevice(token_id, payload).then(response => {
                    console.log('This was the Notification Feature');
                });

            });

        });
    });

});