gmail-service.js

'use strict';

var fs = require('fs');
var readline = require('readline');
var google = require('googleapis');
var googleAuth = require('google-auth-library');

// If modifying these scopes, delete your previously saved credentials
// which location is specified at config/config.json in the property
// generatedTokenPath
var SCOPES = ['https://www.googleapis.com/auth/gmail.send'];
var config = JSON.parse(fs.readFileSync(__dirname + '/../../config/config.json', 'utf8'))[process.env.NODE_ENV || 'dev'];

var CLIENT_SECRET_PATH = config.gmailApi.clientSecretPath;
var GENERATED_TOKEN_PATH = config.gmailApi.generatedTokenPath;

module.exports = (function () {

  /**
   * Create an OAuth2 client with the given credentials, and then execute the
   * given callback function.
   *
   * @param {Object} credentials The authorization client credentials.
   * @param {function} callback The callback to call with the authorized client.
   */
  var authorize = function(credentials, callback) {
      var clientSecret = credentials.installed.client_secret;
      var clientId = credentials.installed.client_id;
      var redirectUrl = credentials.installed.redirect_uris[0];
      var auth = new googleAuth();
      var oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUrl);

      // Check if we have previously stored a token.
      fs.readFile(GENERATED_TOKEN_PATH, function(err, token) {
        if (err) {
          getNewToken(oauth2Client, callback);
        } else {
          oauth2Client.credentials = JSON.parse(token);
          callback(oauth2Client);
        }
      });
    };

   /**
   * Get and store new token after prompting for user authorization, and then
   * execute the given callback with the authorized OAuth2 client.
   *
   * @param {google.auth.OAuth2} oauth2Client The OAuth2 client to get token for.
   * @param {getEventsCallback} callback The callback to call with the authorized
   *     client.
   */
   var getNewToken = function(oauth2Client, callback) {
      var authUrl = oauth2Client.generateAuthUrl({
        access_type: 'offline',
        scope: SCOPES
      });
      console.log('Authorize this app by visiting this url: ', authUrl);
      var rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout
      });
      rl.question('Enter the code from that page here: ', function(code) {
        rl.close();
        oauth2Client.getToken(code, function(err, token) {
          if (err) {
            console.log('Error while trying to retrieve access token', err);
            return;
          }
          oauth2Client.credentials = token;
          storeToken(token);
          callback(oauth2Client);
        });
      });
    }; 

  /**
   * Store token to disk be used in later program executions.
   *
   * @param {Object} token The token to store to disk.
   */
  var storeToken = function(token) {
      fs.writeFile(GENERATED_TOKEN_PATH, JSON.stringify(token));
      console.log('Token stored to ' + GENERATED_TOKEN_PATH);
  };

  /**
   * Structure the email, and send it
   *
   * @param {auth} the authentication gotten from the credentials.
   * @param {from} the email from where the email will be sent.
   * @param {to} the email address that is going to receive the email.
   * @param {subject} the email's subject.
   * @param {content} the email's content.
   */
  function sendEmail(auth, from, to, subject, content, onSuccess, onFail) {
    var contentType = 'text/html; charset=UTF-8';

    //Treating the subject so UTF-8 characters are handled correctly 
    subject = '=?UTF-8?B?' + new Buffer(subject).toString('base64').replace(/\+/g, '-').replace(/\//g, '_') + '?=';
              
     // The Gmail API requires url safe Base64 
     // (replace '+' with '-', and '/' with '_')
     var encodedEmail = new Buffer(
       'From: ' + from + '\r\n' +
       'To: ' + to + '\r\n' +
       'Subject: ' + subject + '\r\n' +
       'Content-Type: ' + contentType + '\r\n\r\n' +

       content 
     ).toString('base64').replace(/\+/g, '-').replace(/\//g, '_');

     var gmail = google.gmail('v1');
     var request = gmail.users.messages.send({
       auth: auth,
       userId: 'me',
       resource: {
         raw: encodedEmail,
         html: true
       }
     }, function (err, result) {
      if(err)
      { 
        onFail(err);
      }else{ 
        onSuccess();
      }
     });
  };

  /**
   * Load the credentials from client_secret.json and send them to be authorized
   *
   * @param {from} the email from where the email will be sent.
   * @param {to} the email address that is going to receive the email.
   * @param {subject} the email's subject.
   * @param {messageContent} the email's content.
   */
  var authorizeAndSendEmail = function(from, to, subject, messageContent, onSuccess, onFail) {
    // Load client secrets from a local file.
    fs.readFile(CLIENT_SECRET_PATH, function processClientSecrets(err, content) {
      if (err) {
        console.log('Error loading client secret file: ' + err);
        return;
      }
      // Authorize a client with the loaded credentials,
      // then call the Gmail API.
      authorize(JSON.parse(content), function(auth){
        sendEmail(auth, from, to, subject, messageContent, onSuccess, onFail);
      });
    });
  }; 

  return {

    authorizeAndSendEmail: authorizeAndSendEmail

  };

})();