Gmail API (via IMAP) using gmail_xoauth - Example

gmail.rb

# An example demonstrating Gmail API via IMAP using gmail_xoauth gem
# Add this file to your rails project to use if you don't want to use this in rails project then require
require 'net/imap'
require 'gmail_xoauth'

class Gmail
  attr_accessor :email, :access_token
  
  def initialize(args)
    email = args[:email]
    access_token = args[:access_token]
  end
  
  # xoauth_imap_authorize 
  # authorizes access to user's @email mailbox with @access_token
  def xoauth_imap_authorize
    imap = Net::IMAP.new('imap.gmail.com', 993, usessl = true, certs = nil, verify = false)
    imap.authenticate('XOAUTH2', @email, @access_token)
    imap.select("[Gmail]/All Mail")
    imap
  end

  def fetch_email
    imap = xoauth_imap_authorize
    # searches email message with subject "hello" and not a "New" messages
    # Response
    # [7293, 7474, 7475, 7476, 7555, 7557, 7558, 7559, 7573, 7675, 7702, 7703, 7796]
    # alternatively you can use various search keys 
    # specified at http://ruby-doc.org/stdlib-2.0/libdoc/net/imap/rdoc/Net/IMAP.html#method-i-searchlike 
    
    message_ids = imap.search(["SUBJECT", "hello", "NOT", "NEW"])
    # fetches a message envelope by specific message_id
    imap.fetch(message_ids[0], "ENVELOPE")
  end
end
# Note: 
# access_token is user access token got from Gmail after authorizing user via Google using omniauth-google-oauth2  
client = Gmail.new(email: "user@email.com", access_token: "user-access-token-XXXX")
response = client.fetch_email
# Sample Response 
# [#<struct Net::IMAP::FetchData
#   seqno=7293
#   attr=
#   {"ENVELOPE"=>
#   #<struct Net::IMAP::Envelope
#   date="Tue, 14 Oct 2014 11:02:07 -0400 (EDT)",
#   subject=
#   "hello",
#   from=
#   [#<struct Net::IMAP::Address
#   name="hello",
#   route=nil,
#   mailbox="inbox",
#   host="sender.com">],
#   sender=
#   [#<struct Net::IMAP::Address
#   name="hello",
#   route=nil,
#   mailbox="inbox",
#   host="sender.com">],
#   reply_to=
#   [#<struct Net::IMAP::Address
#   name="hello",
#   route=nil,
#   mailbox="inbox",
#   host="sender.com">],
#   to=
#   [#<struct Net::IMAP::Address
#   name=nil,
#   route=nil,
#   mailbox="myname",
#   host="receiver.com">],
#   cc=nil,
#   bcc=nil,
#   in_reply_to=nil,
#   message_id="<2014101411111.3192989.1484@sailthru.com>">}>
# ]

omniauth_config.rb

# ENV["GOOGLE_CLIENT_ID"] and ENV["GOOGLE_CLIENT_SECRET"] can be obtained 
# from https://console.developers.google.com/project
# after registering google project on developers console 
Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"],
    {
      :scope => "userinfo.email, userinfo.profile, calendar https://mail.google.com",
      :prompt => "consent"
    }
end

# **OPTIONALLY** you can put this is in config/initializers/devise.rb if you are using devise  
config.omniauth :google_oauth2, 
                ENV["GOOGLE_CLIENT_ID", 
                ENV["GOOGLE_CLIENT_SECRET"], 
                {
                  scope:  "userinfo.email, userinfo.profile, calendar https://mail.google.com",
                  prompt: "consent"
                }


# Omniauth callback will receive follwoing sample omniauth hash in request.env["omniauth.auth"]
# from this you can get the access token required to query Gmail API 

access_token = request.env["omniauth.auth"][:credentials][:token]

# The sample auth hash looks like this
{
    :provider => "google_oauth2",
    :uid => "123456789",
    :info => {
        :name => "John Doe",
        :email => "john@company_name.com",
        :first_name => "John",
        :last_name => "Doe",
        :image => "https://lh3.googleusercontent.com/url/photo.jpg"
    },
    :credentials => {
        :token => "token",
        :refresh_token => "another_token",
        :expires_at => 1354920555,
        :expires => true
    },
    :extra => {
        :raw_info => {
            :sub => "123456789",
            :email => "user@domain.example.com",
            :email_verified => true,
            :name => "John Doe",
            :given_name => "John",
            :family_name => "Doe",
            :profile => "https://plus.google.com/123456789",
            :picture => "https://lh3.googleusercontent.com/url/photo.jpg",
            :gender => "male",
            :birthday => "0000-06-25",
            :locale => "en",
            :hd => "company_name.com"
        }
    }
}