Omniauth implementation.

app/controllers/users/omniauth_callbacks_controller.rb

@@ -0,0 +1,20 @@
+class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
+
+  User::SOCIAL_SITES.each do |name|
+    define_method name do
+      social_site
+    end
+  end
+
+  private
+
+    def social_site
+      @user = OmniauthUser.from_omniauth(request.env["omniauth.auth"], current_user)
+      if @user.errors.messages.present?
+        redirect_to user_session_path, alert: @user.errors.full_messages.first
+      else
+        flash[:notice] = I18n.t 'devise.omniauth_callbacks.success', kind: request.env["omniauth.auth"].provider
+        sign_in_and_redirect @user, event: :authentication
+      end
+    end
+end

app/models/omniauth_user.rb

@@ -2,4 +2,13 @@ class OmniauthUser < ActiveRecord::Base
   belongs_to :user
 
   validates :user, presence: true
+
+  def self.from_omniauth(auth, current_user)
+    omniauth_user = find_by(provider: auth.provider, uid: auth.uid, email: auth.info.email)
+    return omniauth_user.user if omniauth_user.present?
+
+    user = current_user || User.find_by(email: auth.info.email) || User.create(email: auth.info.email, password: Devise.friendly_token[0,20])
+    user.omniauth_users.create(provider: auth.provider, uid: auth.uid, email: auth.info.email)
+    user
+  end
 end

app/models/user.rb

@@ -3,10 +3,13 @@ require 'digest/md5'
 ##
 # a person using the Notebook.ai web application. Owns all other content.
 class User < ActiveRecord::Base
+  SOCIAL_SITES = [:facebook, :google_oauth2, :twitter]
+
   # Include default devise modules. Others available are:
   # :confirmable, :lockable, :timeoutable and :omniauthable
   devise :database_authenticatable, :registerable,
-         :recoverable, :rememberable, :trackable, :validatable
+         :recoverable, :rememberable, :trackable, :validatable,
+         :omniauthable, omniauth_providers: SOCIAL_SITES
 
   include HasContent
   include Authority::UserAbilities
@@ -30,6 +33,8 @@ class User < ActiveRecord::Base
 
   has_many :content_change_events
 
+  has_many :omniauth_users
+
   # TODO: Swap this out with a has_many when we transition from a scratchpad to users having multiple documents
   has_one :document
 

config/initializers/devise.rb

@@ -262,4 +262,8 @@ Devise.setup do |config|
   # When using OmniAuth, Devise cannot automatically set OmniAuth path,
   # so you need to do it manually. For the users scope, it would be:
   # config.omniauth_path_prefix = '/my_engine/users/auth'
+
+  config.omniauth :facebook,      ENV['FACEBOOK_KEY'], ENV['FACEBOOK_SECRET']
+  config.omniauth :google_oauth2, ENV['GOOGLE_KEY'], ENV['GOOGLE_SECRET']
+  config.omniauth :twitter,       ENV['TWITTER_ID'], ENV['TWITTER_SECRET']
 end

config/routes.rb

@@ -2,7 +2,7 @@
 
 Rails.application.routes.draw do
 
-  devise_for :users, :controllers => { registrations: 'registrations' }
+  devise_for :users, controllers: { registrations: 'registrations', omniauth_callbacks: 'users/omniauth_callbacks' }
   resources :users
 
   get '/unsubscribe/emails/:code', to: 'emails#one_click_unsubscribe'