Import Action Mailbox

27 files changed, 653 insertions, 0 deletions

diff --git a/actionmailbox/lib/action_mailbox.rb b/actionmailbox/lib/action_mailbox.rb
new file mode 100644
index 0000000000..b4ff25a9ab
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require "action_mailbox/mail_ext"
+
+module ActionMailbox
+  extend ActiveSupport::Autoload
+
+  autoload :Base
+  autoload :Router
+  autoload :TestCase
+
+  mattr_accessor :ingress
+  mattr_accessor :logger
+  mattr_accessor :incinerate_after, default: 30.days
+  mattr_accessor :queues, default: {}
+end
diff --git a/actionmailbox/lib/action_mailbox/base.rb b/actionmailbox/lib/action_mailbox/base.rb
new file mode 100644
index 0000000000..bd76c8ff5f
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/base.rb
@@ -0,0 +1,113 @@
+# frozen_string_literal: true
+
+require "active_support/rescuable"
+
+require "action_mailbox/callbacks"
+require "action_mailbox/routing"
+
+# The base class for all application mailboxes. Not intended to be inherited from directly. Inherit from
+# `ApplicationMailbox` instead, as that's where the app-specific routing is configured. This routing
+# is specified in the following ways:
+#
+#   class ApplicationMailbox < ActionMailbox::Base
+#     # Any of the recipients of the mail (whether to, cc, bcc) are matched against the regexp.
+#     routing /^replies@/i => :replies
+#
+#     # Any of the recipients of the mail (whether to, cc, bcc) needs to be an exact match for the string.
+#     routing "help@example.com" => :help
+#
+#     # Any callable (proc, lambda, etc) object is passed the inbound_email record and is a match if true.
+#     routing ->(inbound_email) { inbound_email.mail.to.size > 2 } => :multiple_recipients
+#
+#     # Any object responding to #match? is called with the inbound_email record as an argument. Match if true.
+#     routing CustomAddress.new => :custom
+#
+#     # Any inbound_email that has not been already matched will be sent to the BackstopMailbox.
+#     routing :all => :backstop
+#   end
+#
+# Application mailboxes need to overwrite the `#process` method, which is invoked by the framework after
+# callbacks have been run. The callbacks available are: `before_processing`, `after_processing`, and
+# `around_processing`. The primary use case is ensure certain preconditions to processing are fulfilled
+# using `before_processing` callbacks.
+#
+# If a precondition fails to be met, you can halt the processing using the `#bounced!` method,
+# which will silently prevent any further processing, but not actually send out any bounce notice. You
+# can also pair this behavior with the invocation of an Action Mailer class responsible for sending out
+# an actual bounce email. This is done using the `#bounce_with` method, which takes the mail object returned
+# by an Action Mailer method, like so:
+#
+#   class ForwardsMailbox < ApplicationMailbox
+#     before_processing :ensure_sender_is_a_user
+#
+#     private
+#       def ensure_sender_is_a_user
+#         unless User.exist?(email_address: mail.from)
+#           bounce_with UserRequiredMailer.missing(inbound_email)
+#         end
+#       end
+#   end
+#
+# During the processing of the inbound email, the status will be tracked. Before processing begins,
+# the email will normally have the `pending` status. Once processing begins, just before callbacks
+# and the `#process` method is called, the status is changed to `processing`. If processing is allowed to
+# complete, the status is changed to `delivered`. If a bounce is triggered, then `bounced`. If an unhandled
+# exception is bubbled up, then `failed`.
+#
+# Exceptions can be handled at the class level using the familiar `Rescuable` approach:
+#
+#   class ForwardsMailbox < ApplicationMailbox
+#     rescue_from(ApplicationSpecificVerificationError) { bounced! }
+#   end
+class ActionMailbox::Base
+  include ActiveSupport::Rescuable
+  include ActionMailbox::Callbacks, ActionMailbox::Routing
+
+  attr_reader :inbound_email
+  delegate :mail, :delivered!, :bounced!, to: :inbound_email
+
+  delegate :logger, to: ActionMailbox
+
+  def self.receive(inbound_email)
+    new(inbound_email).perform_processing
+  end
+
+  def initialize(inbound_email)
+    @inbound_email = inbound_email
+  end
+
+  def perform_processing
+    track_status_of_inbound_email do
+      run_callbacks :process do
+        process
+      end
+    end
+  rescue => exception
+    # TODO: Include a reference to the inbound_email in the exception raised so error handling becomes easier
+    rescue_with_handler(exception) || raise
+  end
+
+  def process
+    # Overwrite in subclasses
+  end
+
+  def finished_processing?
+    inbound_email.delivered? || inbound_email.bounced?
+  end
+
+
+  def bounce_with(message)
+    inbound_email.bounced!
+    message.deliver_later
+  end
+
+  private
+    def track_status_of_inbound_email
+      inbound_email.processing!
+      yield
+      inbound_email.delivered! unless inbound_email.bounced?
+    rescue
+      inbound_email.failed!
+      raise
+    end
+end
diff --git a/actionmailbox/lib/action_mailbox/callbacks.rb b/actionmailbox/lib/action_mailbox/callbacks.rb
new file mode 100644
index 0000000000..2b7212284b
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/callbacks.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require "active_support/callbacks"
+
+module ActionMailbox
+  # Defines the callbacks related to processing.
+  module Callbacks
+    extend  ActiveSupport::Concern
+    include ActiveSupport::Callbacks
+
+    TERMINATOR = ->(mailbox, chain) do
+      chain.call
+      mailbox.finished_processing?
+    end
+
+    included do
+      define_callbacks :process, terminator: TERMINATOR, skip_after_callbacks_if_terminated: true
+    end
+
+    class_methods do
+      def before_processing(*methods, &block)
+        set_callback(:process, :before, *methods, &block)
+      end
+
+      def after_processing(*methods, &block)
+        set_callback(:process, :after, *methods, &block)
+      end
+
+      def around_processing(*methods, &block)
+        set_callback(:process, :around, *methods, &block)
+      end
+    end
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/engine.rb b/actionmailbox/lib/action_mailbox/engine.rb
new file mode 100644
index 0000000000..0400469ff7
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/engine.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require "rails/engine"
+require "action_mailbox"
+
+module ActionMailbox
+  class Engine < Rails::Engine
+    isolate_namespace ActionMailbox
+    config.eager_load_namespaces << ActionMailbox
+
+    config.action_mailbox = ActiveSupport::OrderedOptions.new
+    config.action_mailbox.incinerate_after = 30.days
+
+    config.action_mailbox.queues = ActiveSupport::InheritableOptions.new \
+      incineration: :action_mailbox_incineration, routing: :action_mailbox_routing
+
+    initializer "action_mailbox.config" do
+      config.after_initialize do |app|
+        ActionMailbox.logger = app.config.action_mailbox.logger || Rails.logger
+        ActionMailbox.incinerate_after = app.config.action_mailbox.incinerate_after || 30.days
+        ActionMailbox.queues = app.config.action_mailbox.queues || {}
+      end
+    end
+
+    initializer "action_mailbox.ingress" do
+      config.after_initialize do |app|
+        if ActionMailbox.ingress = app.config.action_mailbox.ingress.presence
+          config.to_prepare do
+            if ingress_controller_class = "ActionMailbox::Ingresses::#{ActionMailbox.ingress.to_s.classify}::InboundEmailsController".safe_constantize
+              ingress_controller_class.prepare
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/gem_version.rb b/actionmailbox/lib/action_mailbox/gem_version.rb
new file mode 100644
index 0000000000..3959de9ce1
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/gem_version.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module ActionMailbox
+  # Returns the currently-loaded version of Action Mailbox as a <tt>Gem::Version</tt>.
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 6
+    MINOR = 0
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/mail_ext.rb b/actionmailbox/lib/action_mailbox/mail_ext.rb
new file mode 100644
index 0000000000..c4d277a1f9
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+require "mail"
+
+# The hope is to upstream most of these basic additions to the Mail gem's Mail object. But until then, here they lay!
+Dir["#{File.expand_path(File.dirname(__FILE__))}/mail_ext/*"].each { |path| require "action_mailbox/mail_ext/#{File.basename(path)}" }
diff --git a/actionmailbox/lib/action_mailbox/mail_ext/address_equality.rb b/actionmailbox/lib/action_mailbox/mail_ext/address_equality.rb
new file mode 100644
index 0000000000..69243a666e
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext/address_equality.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Mail::Address
+  def ==(other_address)
+    other_address.is_a?(Mail::Address) && to_s == other_address.to_s
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/mail_ext/address_wrapping.rb b/actionmailbox/lib/action_mailbox/mail_ext/address_wrapping.rb
new file mode 100644
index 0000000000..fcdfbb6f6f
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext/address_wrapping.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Mail::Address
+  def self.wrap(address)
+    address.is_a?(Mail::Address) ? address : Mail::Address.new(address)
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/mail_ext/addresses.rb b/actionmailbox/lib/action_mailbox/mail_ext/addresses.rb
new file mode 100644
index 0000000000..377373bee6
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext/addresses.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+class Mail::Message
+  def from_address
+    header[:from]&.address_list&.addresses&.first
+  end
+
+  def recipients_addresses
+    to_addresses + cc_addresses + bcc_addresses + x_original_to_addresses
+  end
+
+  def to_addresses
+    Array(header[:to]&.address_list&.addresses)
+  end
+
+  def cc_addresses
+    Array(header[:cc]&.address_list&.addresses)
+  end
+
+  def bcc_addresses
+    Array(header[:bcc]&.address_list&.addresses)
+  end
+
+  def x_original_to_addresses
+    Array(header[:x_original_to]).collect { |header| Mail::Address.new header.to_s }
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/mail_ext/from_source.rb b/actionmailbox/lib/action_mailbox/mail_ext/from_source.rb
new file mode 100644
index 0000000000..17b7fc80ad
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext/from_source.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+module Mail
+  def self.from_source(source)
+    Mail.new Mail::Utilities.binary_unsafe_to_crlf(source.to_s)
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/mail_ext/recipients.rb b/actionmailbox/lib/action_mailbox/mail_ext/recipients.rb
new file mode 100644
index 0000000000..a8ac42d602
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/mail_ext/recipients.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Mail::Message
+  def recipients
+    Array(to) + Array(cc) + Array(bcc) + Array(header[:x_original_to]).map(&:to_s)
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/postfix_relayer.rb b/actionmailbox/lib/action_mailbox/postfix_relayer.rb
new file mode 100644
index 0000000000..d43c56ed2b
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/postfix_relayer.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require "action_mailbox/version"
+require "net/http"
+require "uri"
+
+module ActionMailbox
+  class PostfixRelayer
+    class Result < Struct.new(:output)
+      def success?
+        !failure?
+      end
+
+      def failure?
+        output.match?(/\A[45]\.\d{1,3}\.\d{1,3}(\s|\z)/)
+      end
+    end
+
+    CONTENT_TYPE = "message/rfc822"
+    USER_AGENT   = "Action Mailbox Postfix relayer v#{ActionMailbox.version}"
+
+    attr_reader :uri, :username, :password
+
+    def initialize(url:, username: "actionmailbox", password:)
+      @uri, @username, @password = URI(url), username, password
+    end
+
+    def relay(source)
+      case response = post(source)
+      when Net::HTTPSuccess
+        Result.new "2.0.0 Successfully relayed message to Postfix ingress"
+      when Net::HTTPUnauthorized
+        Result.new "4.7.0 Invalid credentials for Postfix ingress"
+      else
+        Result.new "4.0.0 HTTP #{response.code}"
+      end
+    rescue IOError, SocketError, SystemCallError => error
+      Result.new "4.4.2 Network error relaying to Postfix ingress: #{error.message}"
+    rescue Timeout::Error
+      Result.new "4.4.2 Timed out relaying to Postfix ingress"
+    rescue => error
+      Result.new "4.0.0 Error relaying to Postfix ingress: #{error.message}"
+    end
+
+    private
+      def post(source)
+        client.post uri, source,
+          "Content-Type"  => CONTENT_TYPE,
+          "User-Agent"    => USER_AGENT,
+          "Authorization" => "Basic #{Base64.strict_encode64(username + ":" + password)}"
+      end
+
+      def client
+        @client ||= Net::HTTP.new(uri.host, uri.port).tap do |connection|
+          if uri.scheme == "https"
+            require "openssl"
+
+            connection.use_ssl     = true
+            connection.verify_mode = OpenSSL::SSL::VERIFY_PEER
+          end
+
+          connection.open_timeout = 1
+          connection.read_timeout = 10
+        end
+      end
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/router.rb b/actionmailbox/lib/action_mailbox/router.rb
new file mode 100644
index 0000000000..0f041a8389
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/router.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# Encapsulates the routes that live on the ApplicationMailbox and performs the actual routing when
+# an inbound_email is received.
+class ActionMailbox::Router
+  class RoutingError < StandardError; end
+
+  def initialize
+    @routes = []
+  end
+
+  def add_routes(routes)
+    routes.each do |(address, mailbox_name)|
+      add_route address, to: mailbox_name
+    end
+  end
+
+  def add_route(address, to:)
+    routes.append Route.new(address, to: to)
+  end
+
+  def route(inbound_email)
+    if mailbox = match_to_mailbox(inbound_email)
+      mailbox.receive(inbound_email)
+    else
+      inbound_email.bounced!
+
+      raise RoutingError
+    end
+  end
+
+  private
+    attr_reader :routes
+
+    def match_to_mailbox(inbound_email)
+      routes.detect { |route| route.match?(inbound_email) }.try(:mailbox_class)
+    end
+end
+
+require "action_mailbox/router/route"
diff --git a/actionmailbox/lib/action_mailbox/router/route.rb b/actionmailbox/lib/action_mailbox/router/route.rb
new file mode 100644
index 0000000000..adb9f94c1a
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/router/route.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# Encapsulates a route, which can then be matched against an inbound_email and provide a lookup of the matching
+# mailbox class. See examples for the different route addresses and how to use them in the `ActionMailbox::Base`
+# documentation.
+class ActionMailbox::Router::Route
+  attr_reader :address, :mailbox_name
+
+  def initialize(address, to:)
+    @address, @mailbox_name = address, to
+
+    ensure_valid_address
+  end
+
+  def match?(inbound_email)
+    case address
+    when :all
+      true
+    when String
+      inbound_email.mail.recipients.any? { |recipient| address.casecmp?(recipient) }
+    when Regexp
+      inbound_email.mail.recipients.any? { |recipient| address.match?(recipient) }
+    when Proc
+      address.call(inbound_email)
+    else
+      address.match?(inbound_email)
+    end
+  end
+
+  def mailbox_class
+    "#{mailbox_name.to_s.camelize}Mailbox".constantize
+  end
+
+  private
+    def ensure_valid_address
+      unless [ Symbol, String, Regexp, Proc ].any? { |klass| address.is_a?(klass) } || address.respond_to?(:match?)
+        raise ArgumentError, "Expected a Symbol, String, Regexp, Proc, or matchable, got #{address.inspect}"
+      end
+    end
+end
diff --git a/actionmailbox/lib/action_mailbox/routing.rb b/actionmailbox/lib/action_mailbox/routing.rb
new file mode 100644
index 0000000000..1ea96c8a9d
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/routing.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module ActionMailbox
+  # See `ActionMailbox::Base` for how to specify routing.
+  module Routing
+    extend ActiveSupport::Concern
+
+    included do
+      cattr_accessor :router, default: ActionMailbox::Router.new
+    end
+
+    class_methods do
+      def routing(routes)
+        router.add_routes(routes)
+      end
+
+      def route(inbound_email)
+        router.route(inbound_email)
+      end
+    end
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/test_case.rb b/actionmailbox/lib/action_mailbox/test_case.rb
new file mode 100644
index 0000000000..a501e8a7ca
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/test_case.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require "action_mailbox/test_helper"
+require "active_support/test_case"
+
+module ActionMailbox
+  class TestCase < ActiveSupport::TestCase
+    include ActionMailbox::TestHelper
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/test_helper.rb b/actionmailbox/lib/action_mailbox/test_helper.rb
new file mode 100644
index 0000000000..02c52fb779
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/test_helper.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require "mail"
+
+module ActionMailbox
+  module TestHelper
+    # 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_from_source file_fixture(fixture_name).read, status: status
+    end
+
+    # Create an `InboundEmail` by specifying it using `Mail.new` options. Example:
+    #
+    #   create_inbound_email_from_mail(from: "david@loudthinking.com", subject: "Hello!")
+    def create_inbound_email_from_mail(status: :processing, **mail_options)
+      create_inbound_email_from_source Mail.new(mail_options).to_s, status: status
+    end
+
+    # Create an `InboundEmail` using the raw rfc822 `source` as text.
+    def create_inbound_email_from_source(source, status: :processing)
+      ActionMailbox::InboundEmail.create_and_extract_message_id! source, status: status
+    end
+
+
+    # Create an `InboundEmail` from fixture using the same arguments as `create_inbound_email_from_fixture`
+    # and immediately route it to processing.
+    def receive_inbound_email_from_fixture(*args)
+      create_inbound_email_from_fixture(*args).tap(&:route)
+    end
+
+    # Create an `InboundEmail` from fixture using the same arguments as `create_inbound_email_from_mail`
+    # and immediately route it to processing.
+    def receive_inbound_email_from_mail(**kwargs)
+      create_inbound_email_from_mail(**kwargs).tap(&:route)
+    end
+
+    # Create an `InboundEmail` from fixture using the same arguments as `create_inbound_email_from_source`
+    # and immediately route it to processing.
+    def receive_inbound_email_from_source(**kwargs)
+      create_inbound_email_from_source(**kwargs).tap(&:route)
+    end
+  end
+end
diff --git a/actionmailbox/lib/action_mailbox/version.rb b/actionmailbox/lib/action_mailbox/version.rb
new file mode 100644
index 0000000000..e65d27f5dd
--- /dev/null
+++ b/actionmailbox/lib/action_mailbox/version.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require_relative "gem_version"
+
+module ActionMailbox
+  # Returns the currently-loaded version of Action Mailbox as a <tt>Gem::Version</tt>.
+  def self.version
+    gem_version
+  end
+end
diff --git a/actionmailbox/lib/rails/generators/installer.rb b/actionmailbox/lib/rails/generators/installer.rb
new file mode 100644
index 0000000000..25cf528ef5
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/installer.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+say "Copying application_mailbox.rb to app/mailboxes"
+copy_file "#{__dir__}/mailbox/templates/application_mailbox.rb", "app/mailboxes/application_mailbox.rb"
+
+environment <<~end_of_config, env: "production"
+  # Prepare the ingress controller used to receive mail
+  # config.action_mailbox.ingress = :amazon
+
+end_of_config
diff --git a/actionmailbox/lib/rails/generators/mailbox/USAGE b/actionmailbox/lib/rails/generators/mailbox/USAGE
new file mode 100644
index 0000000000..d679dd63ae
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/mailbox/USAGE
@@ -0,0 +1,12 @@
+Description:
+============
+    Stubs out a new mailbox class in app/mailboxes and invokes your template
+    engine and test framework generators.
+
+Example:
+========
+    rails generate mailbox inbox
+
+    creates a InboxMailbox class and test:
+        Mailbox:  app/mailboxes/inbox_mailbox.rb
+        Test:     test/mailboxes/inbox_mailbox_test.rb
diff --git a/actionmailbox/lib/rails/generators/mailbox/mailbox_generator.rb b/actionmailbox/lib/rails/generators/mailbox/mailbox_generator.rb
new file mode 100644
index 0000000000..c2c403b8f6
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/mailbox/mailbox_generator.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Rails
+  module Generators
+    class MailboxGenerator < NamedBase
+      source_root File.expand_path("templates", __dir__)
+
+      check_class_collision suffix: "Mailbox"
+
+      def create_mailbox_file
+        template "mailbox.rb", File.join("app/mailboxes", class_path, "#{file_name}_mailbox.rb")
+
+        in_root do
+          if behavior == :invoke && !File.exist?(application_mailbox_file_name)
+            template "application_mailbox.rb", application_mailbox_file_name
+          end
+        end
+      end
+
+      hook_for :test_framework
+
+      private
+        def file_name # :doc:
+          @_file_name ||= super.sub(/_mailbox\z/i, "")
+        end
+
+        def application_mailbox_file_name
+          "app/mailboxes/application_mailbox.rb"
+        end
+    end
+  end
+end
diff --git a/actionmailbox/lib/rails/generators/mailbox/templates/application_mailbox.rb.tt b/actionmailbox/lib/rails/generators/mailbox/templates/application_mailbox.rb.tt
new file mode 100644
index 0000000000..be51eb3639
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/mailbox/templates/application_mailbox.rb.tt
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ApplicationMailbox < ActionMailbox::Base
+  # routing /something/i => :somewhere
+end
diff --git a/actionmailbox/lib/rails/generators/mailbox/templates/mailbox.rb.tt b/actionmailbox/lib/rails/generators/mailbox/templates/mailbox.rb.tt
new file mode 100644
index 0000000000..56b138e2d9
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/mailbox/templates/mailbox.rb.tt
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+class <%= class_name %>Mailbox < ApplicationMailbox
+  def process
+  end
+end
diff --git a/actionmailbox/lib/rails/generators/test_unit/mailbox_generator.rb b/actionmailbox/lib/rails/generators/test_unit/mailbox_generator.rb
new file mode 100644
index 0000000000..2ec7d11a2f
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/test_unit/mailbox_generator.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module TestUnit
+  module Generators
+    class MailboxGenerator < ::Rails::Generators::NamedBase
+      source_root File.expand_path("templates", __dir__)
+
+      check_class_collision suffix: "MailboxTest"
+
+      def create_test_files
+        template "mailbox_test.rb", File.join("test/mailboxes", class_path, "#{file_name}_mailbox_test.rb")
+      end
+
+      private
+        def file_name # :doc:
+          @_file_name ||= super.sub(/_mailbox\z/i, "")
+        end
+    end
+  end
+end
diff --git a/actionmailbox/lib/rails/generators/test_unit/templates/mailbox_test.rb.tt b/actionmailbox/lib/rails/generators/test_unit/templates/mailbox_test.rb.tt
new file mode 100644
index 0000000000..41749808e3
--- /dev/null
+++ b/actionmailbox/lib/rails/generators/test_unit/templates/mailbox_test.rb.tt
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class <%= class_name %>MailboxTest < ActionMailbox::TestCase
+  # test "receive mail" do
+  #   receive_inbound_email_from_mail \
+  #     to: '"someone" <someone@example.com>,
+  #     from: '"else" <else@example.com>',
+  #     subject: "Hello world!",
+  #     body: "Hello?"
+  # end
+end
diff --git a/actionmailbox/lib/tasks/ingress.rake b/actionmailbox/lib/tasks/ingress.rake
new file mode 100644
index 0000000000..f775bbdfd7
--- /dev/null
+++ b/actionmailbox/lib/tasks/ingress.rake
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+namespace :action_mailbox do
+  namespace :ingress do
+    desc "Pipe an inbound email from STDIN to the Postfix ingress (URL and INGRESS_PASSWORD required)"
+    task :postfix do
+      require "active_support"
+      require "active_support/core_ext/object/blank"
+      require "action_mailbox/postfix_relayer"
+
+      url, password = ENV.values_at("URL", "INGRESS_PASSWORD")
+
+      if url.blank? || password.blank?
+        print "4.3.5 URL and INGRESS_PASSWORD are required"
+        exit 1
+      end
+
+      ActionMailbox::PostfixRelayer.new(url: url, password: password).relay(STDIN.read).tap do |result|
+        print result.output
+        exit result.success?
+      end
+    end
+  end
+end
diff --git a/actionmailbox/lib/tasks/install.rake b/actionmailbox/lib/tasks/install.rake
new file mode 100644
index 0000000000..0885e2d6a5
--- /dev/null
+++ b/actionmailbox/lib/tasks/install.rake
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+namespace :action_mailbox do
+  # Prevent migration installation task from showing up twice.
+  Rake::Task["install:migrations"].clear_comments
+
+  desc "Copy over the migration"
+  task install: %w[ environment run_installer copy_migrations ]
+
+  task :run_installer do
+    installer_template = File.expand_path("../rails/generators/installer.rb", __dir__)
+    system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{installer_template}"
+  end
+
+  task :copy_migrations do
+    Rake::Task["active_storage:install:migrations"].invoke
+    Rake::Task["railties:install:migrations"].reenable # Otherwise you can't run 2 migration copy tasks in one invocation
+    Rake::Task["action_mailbox:install:migrations"].invoke
+  end
+end