20131015222934_create_authentications.rb

class CreateAuthentications < ActiveRecord::Migration
  def change
    create_table :authentications do |t|
      t.integer :user_id
      t.string :provider
      t.string :uid
      t.string :name
      t.string :oauth_token
      t.datetime :oauth_expires_at

      t.timestamps
    end
  end
end

authentication.rb

class Authentication < ActiveRecord::Base

  belongs_to :user

  def self.from_omniauth(user, auth)
    where(auth.slice(:provider, :uid)).first_or_initialize.tap do |authentication|
      authentication.user = user
      authentication.provider = auth.provider
      authentication.uid = auth.uid
      authentication.name = auth.info.name
      authentication.oauth_token = auth.credentials.token
      authentication.oauth_expires_at = Time.at(auth.credentials.expires_at)
      authentication.save!
    end
  end

end

authentications.css.scss

.authentications {
  margin-bottom: 30px;
}

.authentication {
  width: 130px;
  float: left;
  background-color: #EEE;
  border: solid 1px #999;
  padding: 5px 10px;
  -moz-border-radius: 8px;
  -webkit-border-radius: 8px;
  position: relative;
  margin-right: 10px;
}

.authentication .remove {
  text-decoration: none;
  position: absolute;
  top: 3px;
  right: 3px;
  color: #333;
  padding: 2px 4px;
  font-size: 10px;
}

.authentication .remove:hover {
  color: #CCC;
  background-color: #777;
  -moz-border-radius: 6px;
  -webkit-border-radius: 6px;
}

.authentication img {
  float: left;
  margin-right: 10px;
}

.authentication .provider {
  font-weight: bold;
}

.authentication .uid {
  color: #666;
  font-size: 11px;
}

.auth_provider img {
  display: block;
}

.auth_provider {
  float: left;
  text-decoration: none;
  margin-right: 20px;
  text-align: center;
  margin-bottom: 10px;
}

authentications_controller.rb

class AuthenticationsController < ApplicationController

  def index
    @authentications = current_user.authentications if current_user
  end

  def create
    auth = Authentication.from_omniauth(current_user, env["omniauth.auth"])
    flash[:notice] = "Authentication successful."
    redirect_to authentications_url
  end

  def destroy
    @authentication = current_user.authentications.find(params[:id])
    @authentication.destroy
    flash[:notice] = "Successfully destroyed authentication."
    redirect_to authentications_url
  end

end

facebook.js

// Additional JS functions here
window.fbAsyncInit = function() {
  FB.init({
    appId      : 400659536727696, // App ID
    status     : true, // check login status
    cookie     : true, // enable cookies to allow the server to access the session
    xfbml      : true  // parse XFBML
  });
};

// Load the SDK Asynchronously
(function(d){
   var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
   if (d.getElementById(id)) {return;}
   js = d.createElement('script'); js.id = id; js.async = true;
   js.src = "//connect.facebook.net/en_US/all.js";
   ref.parentNode.insertBefore(js, ref);
}(document));

function fblogin() {
  FB.getLoginStatus(function(response) {
    if(response.status == "connected") {
      location.href =
        '/auth/facebook/callback?' +
        $.param({ signed_request: response.authResponse.signedRequest })
    } else {
     FB.login(function(response) {
      if (response.authResponse) {
          '/auth/facebook/callback?' +
          $.param({ signed_request: response.authResponse.signedRequest })
      }
     })
    }
  })
};

index.html.erb

<% if @authentications %>
  <% unless @authentications.empty? %>
    <p><strong>You can sign in to this account using:</strong></p>
    <div class="authentications">
      <% for authentication in @authentications %>
        <div class="authentication">
          <%= image_tag "#{authentication.provider}_32.png", :size => "32x32" %>
          <div class="provider"><%= authentication.provider.titleize %></div>
          <div class="uid"><%= authentication.uid %></div>
          <%= link_to "X", authentication, :confirm => 'Are you sure you want to remove this authentication option?', :method => :delete, :class => "remove" %>
        </div>
      <% end %>
      <div class="clear"></div>
    </div>
  <% end %>
  <p><strong>Add another service to sign in with:</strong></p>
<% else %>
  <p><strong>Sign in through one of these services:</strong></p>
<% end %>

<!--
<a href="/auth/twitter" class="auth_provider">
  <%= image_tag "twitter_64.png", :size => "64x64", :alt => "Twitter" %>
  Twitter
</a>
-->
<% unless @authentications.select{ |a| a.provider == "facebook" }.any? %>
  <%= link_to_function image_tag("facebook_64.png", :size => "64x64", :alt => "Facebook"), 'fblogin()' %>
<% end %>
<!--
<a href="/auth/google_apps" class="auth_provider">
  <%= image_tag "google_64.png", :size => "64x64", :alt => "Google" %>
  Google
</a>
-->

<div class="clear"></div>