/**
 * Copyright 2018 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';

// Signs-in Friendly Chat.
function signIn() {
  // TODO 1: Sign in Firebase with credential from the Google user.
  var provider = new firebase.auth.GoogleAuthProvider();
  firebase.auth().signInWithPopup(provider);
}

// Signs-out of Friendly Chat.
function signOut() {
  // TODO 2: Sign out of Firebase.
  firebase.auth().signOut();
}

// Initiate firebase auth.
function initFirebaseAuth() {
  // TODO 3: Initialize Firebase.
  firebase.auth().onAuthStateChanged(authStateObserver);
}

// Returns the signed-in user's profile Pic URL.
function getProfilePicUrl() {
  // TODO 4: Return the user's profile pic URL.
  return firebase.auth().currentUser.photoURL || '/images/profile_placeholder.png';
}

// Returns the signed-in user's display name.
function getUserName() {
  // TODO 5: Return the user's display name.
  return firebase.auth().currentUser.displayName;
}

// Returns true if a user is signed-in.
function isUserSignedIn() {
  // TODO 6: Return true if a user is signed-in.
  return !!firebase.auth().currentUser;
}

// Saves the messaging device token to the datastore.
function saveMessagingDeviceToken() {
  // TODO 10: Save the device token in the realtime datastore
  firebase.messaging().getToken().then(function(currentToken) {
    if (currentToken) {
      console.log('Got FCM device token:', currentToken);
      // Saving the Device Token to the datastore.
      var username = firebase.auth().currentUser.displayName;
      firebase.database().ref('/fcmTokens').child(username)
          .set(currentToken);
          
    } else {
      // Need to request permissions to show notifications.
      requestNotificationsPermissions();
    }
  }).catch(function(error){
    console.error('Unable to get messaging token.', error);
  });
}

// Requests permissions to show notifications.
function requestNotificationsPermissions() {
  // TODO 11: Request permissions to send notifications.
  console.log('Requesting notifications permission...');
  firebase.messaging().requestPermission().then(function() {
    // Notification permission granted.
    saveMessagingDeviceToken();
  }).catch(function(error) {
    console.error('Unable to get permission to notify.', error);
  });
}


// Triggers when the auth state change for instance when the user signs-in or signs-out.
function authStateObserver(user) {
  if (user) { // User is signed in!
    // Get the signed-in user's profile pic and name.
    var profilePicUrl = getProfilePicUrl();
    var userName = getUserName();

    // Set the user's profile pic and name.
    userPicElement.style.backgroundImage = 'url(' + profilePicUrl + ')';
    userNameElement.textContent = userName;

    // Show user's profile and sign-out button.
    userNameElement.removeAttribute('hidden');
    userPicElement.removeAttribute('hidden');
    signOutButtonElement.removeAttribute('hidden');

    // Hide sign-in button.
    signInButtonElement.setAttribute('hidden', 'true');

    // We save the Firebase Messaging Device token and enable notifications.
    saveMessagingDeviceToken();
  } else { // User is signed out!
    // Hide user's profile and sign-out button.
    userNameElement.setAttribute('hidden', 'true');
    userPicElement.setAttribute('hidden', 'true');
    signOutButtonElement.setAttribute('hidden', 'true');

    // Show sign-in button.
    signInButtonElement.removeAttribute('hidden');
  }
}


// A loading image URL.
var LOADING_IMAGE_URL = 'https://www.google.com/images/spin-32.gif?a';


// Checks that the Firebase SDK has been correctly setup and configured.
function checkSetup() {
  if (!window.firebase || !(firebase.app instanceof Function) || !firebase.app().options) {
    window.alert('You have not configured and imported the Firebase SDK. ' +
        'Make sure you go through the codelab setup instructions and make ' +
        'sure you are running the codelab using `firebase serve`');
  }
}

// Checks that Firebase has been imported.
checkSetup();

// Shortcuts to DOM Elements.
var userPicElement = document.getElementById('user-pic');
var userNameElement = document.getElementById('user-name');
var signInButtonElement = document.getElementById('sign-in');
var signOutButtonElement = document.getElementById('sign-out');

// Saves message on form submit.
signOutButtonElement.addEventListener('click', signOut);
signInButtonElement.addEventListener('click', signIn);


// initialize Firebase
initFirebaseAuth();