Done

.gitignore

@@ -1,3 +1,4 @@
 *.sqlite3
 *.log
+.env
 tmp/Gemfile.lock

Gemfile

@@ -33,6 +33,10 @@ gem 'turbolinks'
 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development
 
+gem 'omniauth'
+gem 'omniauth-facebook'
+gem 'dotenv-rails'
+
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug'

Gemfile.lock

@@ -52,18 +52,26 @@ GEM
     concurrent-ruby (1.1.5)
     crass (1.0.5)
     daemons (1.3.1)
+    dotenv (2.7.5)
+    dotenv-rails (2.7.5)
+      dotenv (= 2.7.5)
+      railties (>= 3.2, < 6.1)
     erubis (2.7.0)
     eventmachine (1.2.7)
     execjs (2.7.0)
+    faraday (1.0.1)
+      multipart-post (>= 1.2, < 3)
     ffi (1.11.1)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
+    hashie (4.1.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
     jquery-rails (4.3.5)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
       thor (>= 0.14, < 2.0)
+    jwt (2.2.1)
     loofah (2.3.1)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
@@ -73,9 +81,26 @@ GEM
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
+    multi_json (1.14.1)
+    multi_xml (0.6.0)
+    multipart-post (2.1.1)
     nio4r (2.4.0)
     nokogiri (1.10.5)
       mini_portile2 (~> 2.4.0)
+    oauth2 (1.4.4)
+      faraday (>= 0.8, < 2.0)
+      jwt (>= 1.0, < 3.0)
+      multi_json (~> 1.3)
+      multi_xml (~> 0.5)
+      rack (>= 1.2, < 3)
+    omniauth (1.9.1)
+      hashie (>= 3.4.6)
+      rack (>= 1.6.2, < 3)
+    omniauth-facebook (6.0.0)
+      omniauth-oauth2 (~> 1.2)
+    omniauth-oauth2 (1.6.0)
+      oauth2 (~> 1.1)
+      omniauth (~> 1.9)
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
@@ -153,7 +178,10 @@ PLATFORMS
 DEPENDENCIES
   byebug
   coffee-rails (~> 4.1.0)
+  dotenv-rails
   jquery-rails
+  omniauth
+  omniauth-facebook
   pry
   rails (~> 5.0)
   sass-rails (~> 5.0)
@@ -164,4 +192,4 @@ DEPENDENCIES
   uglifier (>= 1.3.0)
 
 BUNDLED WITH
-   2.0.1
+   2.1.4

app/controllers/session_controller.rb

@@ -0,0 +1,19 @@
+class SessionsController < ApplicationController
+    def create
+      @user = User.find_or_create_by(uid: auth['uid']) do |u|
+        u.name = auth['info']['name']
+        u.email = auth['info']['email']
+        u.image = auth['info']['image']
+      end
+
+      session[:user_id] = @user.id
+
+      render 'welcome/home'
+    end
+
+    private
+
+    def auth
+      request.env['omniauth.auth']
+    end
+  end

app/views/welcome/home.html.erb

@@ -1 +1,10 @@
 <%# Add the Facebook login link here %>
+
+<% if session[:user_id] %>
+  <h1><%= @user.name %></h1>
+  <h2>Email: <%= @user.email %></h2>
+  <h2>Facebook UID: <%= @user.uid %></h2>
+  <img src="<%= @user.image %>">
+<% else %>
+  <%= link_to('Log in with Facebook!', '/auth/facebook') %>
+<% end %>

config/initializers/omniauth.rb

@@ -0,0 +1,3 @@
+Rails.application.config.middleware.use OmniAuth::Builder do
+    provider :facebook, ENV['FACEBOOK_KEY'], ENV['FACEBOOK_SECRET']
+  end

config/routes.rb

@@ -55,4 +55,6 @@
   #     # (app/controllers/admin/products_controller.rb)
   #     resources :products
   #   end
+
+  get '/auth/facebook/callback' => 'sessions#create'
 end