1 files changed, 118 insertions, 0 deletions
diff --git a/actionmailer/lib/action_mailer/preview.rb b/actionmailer/lib/action_mailer/preview.rb
new file mode 100644
index 0000000000..aab92fe8db
--- /dev/null
+++ b/actionmailer/lib/action_mailer/preview.rb
@@ -0,0 +1,118 @@
+require 'active_support/descendants_tracker'
+
+module ActionMailer
+  module Previews #:nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      # Set the location of mailer previews through app configuration:
+      #
+      #     config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+      #
+      mattr_accessor :preview_path, instance_writer: false
+
+      # Enable or disable mailer previews through app configuration:
+      #
+      #     config.action_mailer.show_previews = true
+      #
+      # Defaults to true for development environment
+      #
+      mattr_accessor :show_previews, instance_writer: false
+
+      # :nodoc:
+      mattr_accessor :preview_interceptors, instance_writer: false
+      self.preview_interceptors = [ActionMailer::InlinePreviewInterceptor]
+    end
+
+    module ClassMethods
+      # Register one or more Interceptors which will be called before mail is previewed.
+      def register_preview_interceptors(*interceptors)
+        interceptors.flatten.compact.each { |interceptor| register_preview_interceptor(interceptor) }
+      end
+
+      # Register an Interceptor which will be called before mail is previewed.
+      # Either a class or a string can be passed in as the Interceptor. If a
+      # string is passed in it will be <tt>constantize</tt>d.
+      def register_preview_interceptor(interceptor)
+        preview_interceptor = case interceptor
+          when String, Symbol
+            interceptor.to_s.camelize.constantize
+          else
+            interceptor
+          end
+
+        unless preview_interceptors.include?(preview_interceptor)
+          preview_interceptors << preview_interceptor
+        end
+      end
+    end
+  end
+
+  class Preview
+    extend ActiveSupport::DescendantsTracker
+
+    class << self
+      # Returns all mailer preview classes.
+      def all
+        load_previews if descendants.empty?
+        descendants
+      end
+
+      # Returns the mail object for the given email name. The registered preview
+      # interceptors will be informed so that they can transform the message
+      # as they would if the mail was actually being delivered.
+      def call(email)
+        preview = self.new
+        message = preview.public_send(email)
+        inform_preview_interceptors(message)
+        message
+      end
+
+      # Returns all of the available email previews.
+      def emails
+        public_instance_methods(false).map(&:to_s).sort
+      end
+
+      # Returns true if the email exists.
+      def email_exists?(email)
+        emails.include?(email)
+      end
+
+      # Returns true if the preview exists.
+      def exists?(preview)
+        all.any?{ |p| p.preview_name == preview }
+      end
+
+      # Find a mailer preview by its underscored class name.
+      def find(preview)
+        all.find{ |p| p.preview_name == preview }
+      end
+
+      # Returns the underscored name of the mailer preview without the suffix.
+      def preview_name
+        name.sub(/Preview$/, '').underscore
+      end
+
+      protected
+        def load_previews #:nodoc:
+          if preview_path
+            Dir["#{preview_path}/**/*_preview.rb"].each{ |file| require_dependency file }
+          end
+        end
+
+        def preview_path #:nodoc:
+          Base.preview_path
+        end
+
+        def show_previews #:nodoc:
+          Base.show_previews
+        end
+
+        def inform_preview_interceptors(message) #:nodoc:
+          Base.preview_interceptors.each do |interceptor|
+            interceptor.previewing_email(message)
+          end
+        end
+    end
+  end
+end