Enhancement: Threaded email replies for a conversation (#885) (#886)

* Added custom Message-ID and In-Reply-To headers for conversation reply emails
* Added new global config for the default domain (This is used in the above headers)
* Added migration to run the config loader to load the new global config value
* The subject of the conversation reply mailer was made static (This is required for threaded emails)
* Added required tests

app/mailers/conversation_reply_mailer.rb

@@ -6,6 +6,7 @@ class ConversationReplyMailer < ApplicationMailer
     return unless smtp_config_set_or_development?
 
     @conversation = conversation
+    @account = @conversation.account
     @contact = @conversation.contact
     @agent = @conversation.assignee
 
@@ -15,33 +16,56 @@ class ConversationReplyMailer < ApplicationMailer
     @messages = recap_messages + new_messages
     @messages = @messages.select(&:reportable?)
 
-    mail(to: @contact&.email, from: from_email, reply_to: reply_email, subject: mail_subject(@messages.last))
+    mail({
+           to: @contact&.email,
+           from: from_email,
+           reply_to: reply_email,
+           subject: mail_subject(@messages.last),
+           message_id: custom_message_id,
+           in_reply_to: in_reply_to_email
+         })
   end
 
   private
 
-  def mail_subject(last_message, trim_length = 50)
-    subject_line = last_message&.content&.truncate(trim_length) || 'New messages on this conversation'
+  def mail_subject(_last_message, _trim_length = 50)
+    subject_line = I18n.t('conversations.reply.email_subject')
     "[##{@conversation.display_id}] #{subject_line}"
   end
 
   def reply_email
     if custom_domain_email_enabled?
-      "reply+to+#{@conversation.uuid}@#{@conversation.account.domain}"
+      "reply+to+#{@conversation.uuid}@#{@account.domain}"
     else
       @agent&.email
     end
   end
 
   def from_email
-    if custom_domain_email_enabled? && @conversation.account.support_email.present?
-      @conversation.account.support_email
+    if custom_domain_email_enabled? && @account.support_email.present?
+      @account.support_email
     else
       ENV.fetch('MAILER_SENDER_EMAIL', 'accounts@chatwoot.com')
     end
   end
 
+  def custom_message_id
+    "<conversation/#{@conversation.uuid}/messages/#{@messages.last.id}@#{current_domain}>"
+  end
+
+  def in_reply_to_email
+    "<account/#{@account.id}/conversation/#{@conversation.uuid}@#{current_domain}>"
+  end
+
   def custom_domain_email_enabled?
-    @custom_domain_email_enabled ||= @conversation.account.domain_emails_enabled? && @conversation.account.domain.present?
+    @custom_domain_email_enabled ||= @account.domain_emails_enabled? && @account.domain.present?
+  end
+
+  def current_domain
+    if custom_domain_email_enabled? && @account.domain
+      @account.domain
+    else
+      GlobalConfig.get('FALLBACK_DOMAIN')['FALLBACK_DOMAIN']
+    end
   end
 end

config/installation_config.yml

@@ -14,3 +14,5 @@
   value: 'https://www.chatwoot.com/privacy-policy'
 - name: DISPLAY_MANIFEST
   value: true
+- name: FALLBACK_DOMAIN
+  value: chatwoot.com

config/locales/en.yml

@@ -54,3 +54,5 @@ en:
       typical_reply_message_body: "%{account_name} typically replies in a few hours."
       ways_to_reach_you_message_body: "Give the team a way to reach you."
       email_input_box_message_body: "Get notified by email"
+    reply:
+      email_subject: "New messages on this conversation"

db/migrate/20200522115645_reload_config.rb

@@ -0,0 +1,5 @@
+class ReloadConfig < ActiveRecord::Migration[6.0]
+  def change
+    ConfigLoader.new.process
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_05_10_112339) do
+ActiveRecord::Schema.define(version: 2020_05_22_115645) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"

spec/mailers/conversation_reply_mailer_spec.rb

@@ -19,7 +19,7 @@ RSpec.describe ConversationReplyMailer, type: :mailer do
       let(:mail) { described_class.reply_with_summary(message.conversation, Time.zone.now).deliver_now }
 
       it 'renders the subject' do
-        expect(mail.subject).to eq("[##{message.conversation.display_id}] #{message.content.truncate(30)}")
+        expect(mail.subject).to eq("[##{message.conversation.display_id}] New messages on this conversation")
       end
 
       it 'not have private notes' do
@@ -44,6 +44,14 @@ RSpec.describe ConversationReplyMailer, type: :mailer do
       it 'renders the reply to email' do
         expect(mail.reply_to).to eq([message&.conversation&.assignee&.email])
       end
+
+      it 'sets the correct custom message id' do
+        expect(mail.message_id).to eq("<conversation/#{conversation.uuid}/messages/#{message.id}@>")
+      end
+
+      it 'sets the correct in reply to id' do
+        expect(mail.in_reply_to).to eq("<account/#{conversation.account.id}/conversation/#{conversation.uuid}@>")
+      end
     end
 
     context 'when the cutsom domain emails are enabled' do
@@ -67,6 +75,14 @@ RSpec.describe ConversationReplyMailer, type: :mailer do
       it 'sets the from email to be the support email' do
         expect(mail.from).to eq([conversation.account.support_email])
       end
+
+      it 'sets the correct custom message id' do
+        expect(mail.message_id).to eq("conversation/#{conversation.uuid}/messages/#{message.id}@#{conversation.account.domain}")
+      end
+
+      it 'sets the correct in reply to id' do
+        expect(mail.in_reply_to).to eq("account/#{conversation.account.id}/conversation/#{conversation.uuid}@#{conversation.account.domain}")
+      end
     end
   end
 end