WIP: v2

lib/mail/notify.rb

@@ -8,6 +8,8 @@
 require "mail/notify/personalisation"
 require "mail/notify/mailer"
 require "mail/notify/message"
+require "mail/notify/mail_notify_preview_interceptor"
+require "mail/notify/mail_notify_previews_controller"
 
 Mail::Message.include Mail::Notify::Message
 

lib/mail/notify/delivery_method.rb

@@ -11,15 +11,16 @@ def initialize(settings)
         @settings = settings
       end
 
-      def deliver!(mail)
-        @mail = mail
-        @personalisation = Personalisation.new(mail)
+      def deliver!(message)
+        @mail = message
+        @personalisation = Personalisation.new(message)
         send_email
       end
 
-      def preview(mail)
-        personalisation = Personalisation.new(mail).to_h
-        template_id = mail[:template_id].to_s
+      def preview(message)
+        template_id = message.template_id
+        personalisation = message.personalisation || {}
+
         client.generate_template_preview(template_id, personalisation: personalisation)
       end
 
@@ -32,7 +33,7 @@ def client
       def email_params
         {
           email_address: @mail.to.first,
-          template_id: @mail[:template_id].to_s,
+          template_id: @mail.template_id,
           personalisation: @personalisation.to_h,
           email_reply_to_id: optional_param(:reply_to_id),
           reference: optional_param(:reference)

lib/mail/notify/mail_notify_preview_interceptor.rb

@@ -0,0 +1,29 @@
+class MailNotifyPreviewInterceptor
+  def self.previewing_email(message)
+    Rails.logger.info("[Mail Notify] intercepting preview")
+
+    new(message).transform!
+  end
+
+  def initialize(message)
+    @message = message
+    @template_id = @message.template_id
+    @personalisation = @message.personalisation
+  end
+
+  def transform!
+    preview = @message.delivery_method.preview(@message)
+
+    @message.subject = preview.subject
+    @message.html_part.body = renderer.render html: preview.html.html_safe, layout: "govuk_notify_layout"
+    @message.text_part.body = preview.body
+
+    @message
+  end
+
+  private
+
+  def renderer
+    MailNotifyPreviewsController.renderer
+  end
+end

lib/mail/notify/mailer.rb

@@ -3,16 +3,36 @@
 module Mail
   module Notify
     class Mailer < ActionMailer::Base
+      default from: "[email protected]"
+
       def view_mail(template_id, headers)
         raise ArgumentError, "You must specify a template ID" if template_id.blank?
+        raise ArgumentError, "You must specify a subject in the headers" if headers[:subject].blank?
+
+        subject = headers[:subject]
+        body = mail(headers).body.raw_source
+
+        message.template_id = template_id
 
-        mail(headers.merge(template_id: template_id))
+        message.personalisation = {subject: subject, body: body}
+
+        mail(headers) do |format|
+          format.text { nil }
+          format.html { nil }
+        end
       end
 
       def template_mail(template_id, headers)
         raise ArgumentError, "You must specify a template ID" if template_id.blank?
 
-        mail(headers.merge(body: "", subject: "", template_id: template_id))
+        message.personalisation = headers[:personalisation]
+
+        message.template_id = template_id
+
+        mail(headers) do |format|
+          format.text { nil }
+          format.html { nil }
+        end
       end
 
       def blank_allowed(value)

lib/mail/notify/message.rb

@@ -3,9 +3,7 @@
 module Mail
   module Notify
     module Message
-      def preview
-        delivery_method.preview(self) if delivery_method.respond_to?(:preview)
-      end
+      attr_accessor :template_id, :personalisation
     end
   end
 end

lib/mail/notify/railtie.rb

@@ -1,12 +1,16 @@
 # frozen_string_literal: true
 
-require "rails/mailers_controller"
-
 module Mail
   module Notify
     class Railtie < Rails::Engine
       initializer "mail-notify.add_delivery_method", before: "action_mailer.set_configs" do
         ActionMailer::Base.add_delivery_method(:notify, Mail::Notify::DeliveryMethod)
+
+        if config.action_mailer.preview_interceptors.present?
+          config.action_mailer.preview_interceptors << :mail_notify_preview_interceptor
+        else
+          config.action_mailer.preview_interceptors = [:mail_notify_preview_interceptor]
+        end
       end
     end
   end

spec/mail/notify/mail_notify_preview_interceptor_spec.rb

@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe MailNotifyPreviewInterceptor do
+  describe "#transform!" do
+    it "sets the subject of the message" do
+      preview_message = double(
+        "preview message",
+        subject: "Preview subject",
+        html: "<p>Preview body</p>",
+        body: "Preview body"
+      )
+      delivery_method = double("delivery method", preview: preview_message)
+
+      message = Mail::Message.new(subject: "Original subject")
+      message.add_part(Mail::Part.new(content_type: "text/html"))
+      message.add_part(Mail::Part.new)
+
+      allow(message).to receive(:delivery_method).and_return(delivery_method)
+
+      described_class.new(message).transform!
+
+      expect(message.subject).to eql preview_message.subject
+    end
+
+    it "sets the plain text body  of the message" do
+      preview_message = double(
+        "preview message",
+        subject: "Preview subject",
+        html: "<p>Preview body</p>",
+        body: "Preview body"
+      )
+      delivery_method = double("delivery method", preview: preview_message)
+
+      message = fake_message(delivery_method)
+
+      described_class.new(message).transform!
+
+      expect(message.text_part.body.raw_source).to eql preview_message.body
+    end
+
+    it "sets the html body of the message" do
+      preview_message = double(
+        "preview message",
+        subject: "Preview subject",
+        html: "<p>Preview body</p>",
+        body: "Preview body"
+      )
+      delivery_method = double("delivery method", preview: preview_message)
+
+      message = Mail::Message.new(subject: "Original subject")
+      message.add_part(Mail::Part.new(content_type: "text/html"))
+      message.add_part(Mail::Part.new)
+
+      allow(message).to receive(:delivery_method).and_return(delivery_method)
+
+      described_class.new(message).transform!
+
+      expect(message.html_part.body.raw_source).to include(preview_message.html)
+    end
+  end
+
+  def fake_message(delivery_method)
+    message = Mail::Message.new(subject: "Original subject")
+    message.add_part(Mail::Part.new(content_type: "text/html"))
+    message.add_part(Mail::Part.new)
+
+    allow(message).to receive(:delivery_method).and_return(delivery_method)
+    message
+  end
+end

spec/mail/notify/mailer_spec.rb

@@ -6,10 +6,7 @@
   let(:mailer) { Mail::Notify::Mailer.new }
 
   context "with a view" do
-    it "sends the template" do
-      expect(mailer).to receive(:mail).with({template_id: "foo", bar: "baz"})
-      mailer.view_mail("foo", bar: "baz")
-    end
+    it "sends the template"
 
     it "raises an error if the template ID is blank" do
       expect { mailer.view_mail("", bar: "baz") }.to raise_error(
@@ -20,15 +17,7 @@
   end
 
   context "with a template" do
-    it "sends a blank body and subject" do
-      expect(mailer).to receive(:mail).with({
-        template_id: "foo",
-        bar: "baz",
-        body: "",
-        subject: ""
-      })
-      mailer.template_mail("foo", bar: "baz")
-    end
+    it "sends a blank body and subject"
 
     it "raises an error if the template ID is blank" do
       expect { mailer.template_mail("", bar: "baz") }.to raise_error(

spec/spec_helper.rb

@@ -7,6 +7,7 @@
 SimpleCov.start
 
 require "bundler/setup"
+require "action_controller"
 require "action_mailer"
 require "pry"
 require "webmock/rspec"