Add unsubscribe links and headers for emails

https://3.basecamp.com/2914079/buckets/37331921/todos/9002504172

app/controllers/notifications/unsubscribes_controller.rb

@@ -0,0 +1,24 @@
+class Notifications::UnsubscribesController < ApplicationController
+  allow_unauthenticated_access
+  skip_before_action :verify_authenticity_token
+
+  before_action :set_user
+
+  def new
+  end
+
+  def create
+    @user.settings.bundle_email_never!
+    redirect_to notifications_unsubscribe_path(access_token: params[:access_token])
+  end
+
+  def show
+  end
+
+  private
+    def set_user
+      unless @user = User.find_by_token_for(:unsubscribe, params[:access_token])
+        redirect_to root_path, alert: "Invalid unsubscribe link"
+      end
+    end
+end

app/mailers/concerns/mailers/unsubscribable.rb

@@ -0,0 +1,12 @@
+module Mailers::Unsubscribable
+  extend ActiveSupport::Concern
+
+  included do
+    after_action :set_unsubscribe_headers
+  end
+
+  def set_unsubscribe_headers
+    headers["List-Unsubscribe-Post"] = "List-Unsubscribe=One-Click"
+    headers["List-Unsubscribe"]      = "<#{notifications_unsubscribe_url(access_token: @unsubscribe_token)}>"
+  end
+end

app/mailers/notification/bundle_mailer.rb

@@ -1,9 +1,13 @@
 class Notification::BundleMailer < ApplicationMailer
+  include Mailers::Unsubscribable
+
   helper NotificationsHelper
 
   def notification(bundle)
+    @user = bundle.user
     @bundle = bundle
     @notifications = bundle.notifications
+    @unsubscribe_token = @user.generate_token_for(:unsubscribe)
 
     mail \
       to: bundle.user.email_address,

app/models/user/notifiable.rb

@@ -4,6 +4,8 @@ module User::Notifiable
   included do
     has_many :notifications, dependent: :destroy
     has_many :notification_bundles, class_name: "Notification::Bundle", dependent: :destroy
+
+    generates_token_for :unsubscribe, expires_in: 1.month
   end
 
   def bundle(notification)

app/views/mailers/notification/bundle_mailer/notification.html.erb

@@ -5,7 +5,7 @@
     <%= render partial: "notification/bundle_mailer/notification", collection: @notifications, as: :notification %>
     <p class="footer">Fizzy emails you about new notifications every few hours. <br>
       <%= link_to "Change how often you get these", notifications_settings_url %>
-      or <%= link_to "unsubscribe from all email notifications", root_url %>.
+      or <%= link_to "unsubscribe from all email notifications", new_notifications_unsubscribe_url(access_token: @unsubscribe_token) %>.
     </p>
   </td>
 </tr>

app/views/mailers/notification/bundle_mailer/notification.text.erb

@@ -10,4 +10,4 @@ Change how often you get these:
 <%= notifications_settings_url %>
 
 Unsubscribe from all email notifications:
-<%= root_url %>
+<%= new_notifications_unsubscribe_url(access_token: @unsubscribe_token) %>

app/views/notifications/unsubscribes/new.html.erb

@@ -0,0 +1,7 @@
+<p>Unsubscribing from all email notifications as <%= @user.name %>…</p>
+
+<div class="push_double--top centered delayed-fade-in">
+  <%= auto_submit_form_with model: @user, url: notifications_unsubscribe_path(access_token: params[:access_token]), method: :post do |form| %>
+    <%= form.submit "Unsubscribe now", class: "btn" %>
+  <% end %>
+</div>

app/views/notifications/unsubscribes/show.html.erb

@@ -0,0 +1,3 @@
+<h1>Unsubscribed</h1>
+<p>Thank you <%= @user.name %>, you will no longer receive bundled email notifications.</p>
+<p>You can <%= link_to "re-enable notifications here", notifications_settings_path %>.</p>

config/routes.rb

@@ -56,6 +56,7 @@ Rails.application.routes.draw do
 
   namespace :notifications do
     resource :settings
+    resource :unsubscribe
   end
 
   resources :notifications do

test/controllers/notifications/unsubscribes_controller_test.rb

@@ -0,0 +1,40 @@
+require "test_helper"
+
+class Notifications::UnsubscribesControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    @user = users(:david)
+    @access_token = @user.generate_token_for(:unsubscribe)
+
+    sign_in_as @user
+  end
+
+  test "new" do
+    get new_notifications_unsubscribe_path(access_token: @access_token)
+    assert_response :success
+  end
+
+  test "new with bad token" do
+    get new_notifications_unsubscribe_path(access_token: "bad")
+    assert_redirected_to root_path
+  end
+
+  test "create" do
+    @user.reload.settings.bundle_email_every_few_hours!
+    assert_changes -> { @user.reload.settings.bundle_email_frequency }, to: "never" do
+      post notifications_unsubscribe_path(access_token: @access_token)
+      assert_redirected_to notifications_unsubscribe_path(access_token: @access_token)
+    end
+  end
+
+  test "create with bad token" do
+    assert_no_changes -> { @user.reload.settings.bundle_email_frequency } do
+      post notifications_unsubscribe_path(access_token: "bad")
+      assert_redirected_to root_path
+    end
+  end
+
+  test "show" do
+    get notifications_unsubscribe_path(access_token: @access_token)
+    assert_response :success
+  end
+end