Friday, July 14, 2017

Completed Ch 9: Advanced Login

* I keep going forward to chapter 9 to create "remember me" function during user log in.

* As usual, I switching to a branch called "advanced-login".
$ git checkout -b advanced-login

* I added the remember_digest field of string in the Users data model.
$ rails generate migration add_remember_digest_to_users remember_digest:string

* This was the content of the database migration file 20170714053652_add_remember_digest_to_users.rb
sample_app/db/migrate/20170714053652_add_remember_digest_to_users.rb


class AddRememberDigestToUsers < ActiveRecord::Migration[5.0]
  def change
    add_column :users, :remember_digest, :string
  end
end

* Then, I ran the database migration command.
$ rails db:migrate
== 20170714053652 AddRememberDigestToUsers: migrating =========================
-- add_column(:users, :remember_digest, :string)
   -> 0.0280s
== 20170714053652 AddRememberDigestToUsers: migrated (0.0282s) ================

* I added a new method in User model to return a random token.

* I added a remember method to the User model.
sample_app/app/models/users.rb

* I defined the new token and digest methods using self.
sample_app/app/models/users.rb
  # Returns the hash digest of the given string.
  def self.digest(string)
    cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :
                                                  BCrypt::Engine.cost
    BCrypt::Password.create(string, cost: cost)
  end

  # Returns a random token.
  def self.new_token
    SecureRandom.urlsafe_base64
  end

* I added an authenticated? method to the User model.
sample_app/app/models/user.rb
  # Returns true if the given token matches the digest.
  def authenticated?(remember_token)
    BCrypt::Password.new(remember_digest).is_password?(remember_token)
  end

* I added the "remember_user" method to the Sessions Controller
sample_app/app/controllers/sessions_controller.rb
  def create
    user = User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      log_in user
      remember user
      redirect_to user
    else
      flash.now[:danger] = 'Invalid email/password combination'
      render 'new'
    end
  end

* I added the "remember(user)" method in the Sessions Helper
sample_app/app/helpers/sessions_helper.rb
  # Remembers a user in a persistent session.
  def remember(user)
    user.remember
    cookies.permanent.signed[:user_id] = user.id
    cookies.permanent[:remember_token] = user.remember_token
  end

* I re-wrote the "current_user" method in the Sessions helper.
sample_app/app/helpers/sessions_helper.rb
  # Returns the user corresponding to the remember token cookie.
  def current_user
    if (user_id = session[:user_id])
      @current_user ||= User.find_by(id: user_id)
    elsif (user_id = cookies.signed[:user_id])
      user = User.find_by(id: user_id)
      if user && user.authenticated?(cookies[:remember_token])
        log_in user
        @current_user = user
      end
    end
  end

* I added forget method in the User model to forget a user.
sample_app/app/models/user.rb
  def forget
    update_attribute(:remember_digest, nil)
  end

* I added the forget method in Sessions helper. And I added a line "forget(current_user)" in the log_out method to forget a user when a user logs out.
sample_app/app/helpers/sessions_helper.rb

* I added a line "delete logout_path" in Users Login Integration test to simulate a user clicking logout in a second window.
sample_app/test/integration/users_login_test.rb

* I modified the destroy method in Sessions Controller to log out a user only only when the user has already logged in.
sample_app/app/controllers/sessions_controller.rb

* I added a unit test "authenticated?" to test with a nonexistent digest.
sample_app/test/models/user_test.rb
  test "authenticated? should return false for a user with nil digest" do
    assert_not @user.authenticated?('')
  end

* I added a line "return false if remember_digest.nil?" in the "authenticated?" method in the User model.
sample_app/app/models/user.rb
  # Returns true if the given token matches the digest.
  def authenticated?(remember_token)
    return false if remember_digest.nil?
    BCrypt::Password.new(remember_digest).is_password?(remember_token)
  end

* I added the "Remember me" checkbox in the log in screen.
sample_app/app/views/sessions/new.html.erb
      <%= f.label :remember_me, class: "checkbox inline" do %>
        <%= f.check_box :remember_me %>
        <span>Remember me on this computer</span>
      <% end %>

* I defined the CSS style for the Checkbox and the session_remember_me.
sample_app/app/assets/stylesheets/custom.scss
/* forms */
.checkbox {
  margin-top: -10px;
  margin-bottom: 10px;
  span {
    margin-left: 20px;
    font-weight: normal;
  }
}

#session_remember_me {
  width: auto;
  margin-left: 0;
}


* I added a line "params[:session][:remember_me] == '1' ? remember(user) : forget(user)"  in the Sessions controller to remember a user login if he checks on the "Remember me" checkout.
sample_app/app/controllers/sessions_controller.rb
  def create
    user = User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      log_in user
      params[:session][:remember_me] == '1' ? remember(user) : forget(user)
      redirect_to user
    else
      flash.now[:danger] = 'Invalid email/password combination'
      render 'new'
    end
  end

* I added the "log_in_as(user)" method in Test Helper and a new class "ActionDispatch" to test the "Remember me" feature.
sample_app/test/test_helper.rb
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rails/test_help'

class ActiveSupport::TestCase
  # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
  fixtures :all
  include ApplicationHelper
   
  # Add more helper methods to be used by all tests here...
   
  # Returns true if a test user is logged in.
  def is_logged_in?
    !session[:user_id].nil?
  end

  # Log in as a particular user.
  def log_in_as(user)
    session[:user_id] = user.id
  end       
end

class ActionDispatch::IntegrationTest

  # Log in as a particular user.
  def log_in_as(user, password: 'password', remember_me: '1')
    post login_path, params: { session: { email: user.email,
                                          password: password,
                                          remember_me: remember_me } }
  end
end

* I wrote two test cases "login with remembering" and "login without remembering" in the Users Login Integration Test to test the "Remember me" functionality.
sample_app/test/integration/users_login_test.rb
  test "login with remembering" do
    log_in_as(@user, remember_me: '1')
    assert_not_empty cookies['remember_token']
  end

  test "login without remembering" do
    # Log in to set the cookie.
    log_in_as(@user, remember_me: '1')
    # Log in again and verify that the cookie is deleted.
    log_in_as(@user, remember_me: '0')
    assert_empty cookies['remember_token']
  end

* I added a line to raise an exception in the suspected untested block of code.
sample_app/app/helpers/sessions_helper.rb

* I created a new file "sessions_helper_test.rb" for testing of  persistent sessions.
sample_app/test/helpers/sessions_helper_test.rb
require 'test_helper'

class SessionsHelperTest < ActionView::TestCase

  def setup
    @user = users(:michael)
    remember(@user)
  end

  test "current_user returns right user when session is nil" do
    assert_equal @user, current_user
    assert is_logged_in?
  end

  test "current_user returns nil when remember digest is wrong" do
    @user.update_attribute(:remember_digest, User.digest(User.new_token))
    assert_nil current_user
  end
end


* I deleted the "raise exception" line in Sessions Helper.
sample_app/app/helpers/sessions_helper.rb

* Horay, I had completed chapter 9. Just like usual, I ran a test, added all untracked files, committed changes, merged back to Master branch, pushed on to Github.
$ rails test
$ git add -A
$ git commit -m "Implement advanced login"
$ git checkout master
$ git merge advanced-login
$ git push


* The Github repository address for Michael Hartl's sample_app is https://github.com/jimmy2046/sample_app.

* The screenshot of the login page with "Remember me" function.

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