Extract and associate message_id with newly created inbound emails

app/controllers/action_mailroom/inbound_emails_controller.rb

@@ -4,7 +4,7 @@ class ActionMailroom::InboundEmailsController < ActionController::Base
   before_action :require_rfc822_message
 
   def create
-    ActionMailroom::InboundEmail.create!(raw_email: params[:message])
+    ActionMailroom::InboundEmail.create_from_raw_email!(params[:message])
     head :created
   end
 

app/models/action_mailroom/inbound_email.rb

@@ -9,7 +9,22 @@ class ActionMailroom::InboundEmail < ActiveRecord::Base
   has_one_attached :raw_email
   enum status: %i[ pending processing delivered failed bounced ]
 
+  class << self
+    def create_from_raw_email!(raw_email, **options)
+      create! raw_email: raw_email, message_id: extract_message_id(raw_email), **options
+    end
+    
+    def mail_from_raw_content(raw_email_content)
+      Mail.new(Mail::Utilities.binary_unsafe_to_crlf(raw_email_content.to_s))
+    end
+
+    private
+      def extract_message_id(raw_email)
+        mail_from_raw_content(raw_email.read).message_id
+      end
+  end
+
   def mail
-    @mail ||= Mail.new(Mail::Utilities.binary_unsafe_to_crlf(raw_email.download))
+    @mail ||= self.class.mail_from_raw_content(raw_email.download)
   end
 end

db/migrate/20180917164000_create_action_mailbox_tables.rb

@@ -2,6 +2,7 @@ class CreateActionMailroomTables < ActiveRecord::Migration[5.2]
   def change
     create_table :action_mailroom_inbound_emails do |t|
       t.integer :status, default: 0, null: false
+      t.string  :message_id
 
       t.datetime :created_at, precision: 6
       t.datetime :updated_at, precision: 6

lib/action_mailroom/test_helper.rb

@@ -5,16 +5,18 @@ module ActionMailroom
     # Create an InboundEmail record using an eml fixture in the format of message/rfc822
     # referenced with +fixture_name+ located in +test/fixtures/files/fixture_name+.
     def create_inbound_email_from_fixture(fixture_name, status: :processing)
-      create_inbound_email file_fixture(fixture_name).open, filename: fixture_name, status: status
+      create_inbound_email file_fixture(fixture_name), filename: fixture_name, status: status
     end    
 
     def create_inbound_email_from_mail(status: :processing, **mail_options)
-      create_inbound_email(StringIO.new(Mail.new(mail_options).to_s), status: status)
+      raw_email = Tempfile.new.tap { |raw_email| raw_email.write Mail.new(mail_options).to_s }
+      create_inbound_email(raw_email, status: status)
     end
 
     def create_inbound_email(io, filename: 'mail.eml', status: :processing)
-      ActionMailroom::InboundEmail.create! status: status, raw_email:
-        ActiveStorage::Blob.create_after_upload!(io: io, filename: filename, content_type: 'message/rfc822')
+      ActionMailroom::InboundEmail.create_from_raw_email! \
+        ActionDispatch::Http::UploadedFile.new(tempfile: io, filename: filename, type: 'message/rfc822'),
+        status: status
     end
   end
 end

test/dummy/db/migrate/20180208205311_create_action_mailroom_tables.rb

@@ -2,6 +2,7 @@ class CreateActionMailroomTables < ActiveRecord::Migration[5.2]
   def change
     create_table :action_mailroom_inbound_emails do |t|
       t.integer :status, default: 0, null: false
+      t.string  :message_id
 
       t.datetime :created_at, precision: 6
       t.datetime :updated_at, precision: 6

test/dummy/db/schema.rb

@@ -14,6 +14,7 @@ ActiveRecord::Schema.define(version: 2018_02_12_164506) do
 
   create_table "action_mailroom_inbound_emails", force: :cascade do |t|
     t.integer "status", default: 0, null: false
+    t.string "message_id"
     t.datetime "created_at", precision: 6
     t.datetime "updated_at", precision: 6
   end

test/unit/inbound_email_test.rb

@@ -0,0 +1,10 @@
+require_relative '../test_helper'
+
+module ActionMailroom
+  class InboundEmailTest < ActiveSupport::TestCase
+    test "message id is extracted from raw email" do
+      inbound_email = create_inbound_email_from_fixture("welcome.eml")
+      assert_equal "0CB459E0-0336-41DA-BC88-E6E28C697DDB@37signals.com", inbound_email.message_id
+    end
+  end
+end