feat(mailer): add Prism and Mailer

lib/prism/mailer/base.rb

@@ -0,0 +1,128 @@
+module Prism
+  module Mailer
+    # ActionMailer-lite: subclass, declare `default from: '...'`, define an
+    # instance method per mailer action that ends with a call to #mail.
+    # Calling the action as a class method (`WelcomeMailer.welcome(user)`)
+    # renders the templates immediately and returns a Delivery.
+    class Base
+      class << self
+        def default(options = nil)
+          @default_options = (@default_options || {}).merge(options) if options
+          @default_options || {}
+        end
+
+        def template_roots
+          @template_roots || [File.join(Dir.pwd, 'app', 'views', 'mailers')]
+        end
+
+        attr_writer :template_roots
+
+        # Per-mailer-class override of Mailer.default_url_options, merged
+        # over it (this class's values win) by #url_for.
+        def default_url_options(options = nil)
+          @default_url_options = (@default_url_options || {}).merge(options) if options
+          @default_url_options || {}
+        end
+
+        def mailer_name
+          Inflector.underscore(name.to_s.split('::').last.sub(/Mailer\z/, ''))
+        end
+
+        def method_missing(name, *args, &block)
+          return super unless instance_methods(false).include?(name)
+
+          instance = new
+          instance.send(:run_action, name, args)
+          Delivery.new(instance.message, mailer_class: self, action_name: name.to_s, args: args)
+        end
+
+        def respond_to_missing?(name, include_private = false)
+          instance_methods(false).include?(name) || super
+        end
+      end
+
+      attr_reader :message, :action_name
+
+      def initialize
+        @message = Message.new
+        apply_defaults
+      end
+
+      def mail(to:, subject:, from: nil, cc: nil, bcc: nil, reply_to: nil, template: nil, locals: {})
+        message.to = to
+        message.subject = subject
+        message.from = from if from
+        message.cc = cc if cc
+        message.bcc = bcc if bcc
+        message.reply_to = reply_to if reply_to
+        render_bodies(template || action_name, locals)
+        message
+      end
+
+      # Absolute URL for a named route, for use inside mailer actions and
+      # templates (there is no incoming request to infer a host from, unlike
+      # Controller#url_for). Requires Mailer.router to be set and a :host
+      # somewhere in Mailer.default_url_options / self.class.default_url_options
+      # / the params passed here.
+      def url_for(name, params = {})
+        router = Mailer.router
+        raise 'no router configured; set Prism::Mailer.router before generating mailer URLs' unless router
+
+        options = Mailer.default_url_options.merge(self.class.default_url_options).merge(params)
+        host = options.delete(:host)
+        raise ArgumentError, 'default_url_options must include :host to build a mailer URL' unless host
+
+        protocol = options.delete(:protocol) || 'http'
+        port = options.delete(:port)
+        "#{protocol}://#{host}#{port ? ":#{port}" : ''}#{router.path_to(name, options)}"
+      end
+
+      private
+
+      def run_action(name, args)
+        @action_name = name.to_s
+        public_send(name, *args)
+      end
+
+      def apply_defaults
+        self.class.default.each do |key, value|
+          message.public_send("#{key}=", value)
+        end
+      end
+
+      def render_bodies(name, locals)
+        view = Prism::View.new(self.class.template_roots, helpers: self)
+        merged_locals = auto_locals.merge(locals)
+        found_any = false
+
+        begin
+          message.text_body = view.render("#{self.class.mailer_name}/#{name}.text", locals: merged_locals)
+          found_any = true
+        rescue Prism::View::TemplateNotFound
+          nil
+        end
+
+        begin
+          message.html_body = view.render("#{self.class.mailer_name}/#{name}.html", locals: merged_locals)
+          found_any = true
+        rescue Prism::View::TemplateNotFound
+          nil
+        end
+
+        return if found_any
+
+        raise Prism::View::TemplateNotFound,
+              "no mailer template #{name}.text.erb or #{name}.html.erb for " \
+              "#{self.class.mailer_name} in #{self.class.template_roots.join(', ')}"
+      end
+
+      def auto_locals
+        instance_variables.each_with_object({}) do |ivar, locals|
+          next if %i[@message @action_name].include?(ivar)
+
+          locals[ivar.to_s.delete_prefix('@').to_sym] = instance_variable_get(ivar)
+        end
+      end
+    end
+  end
+end

lib/prism/mailer/delivery.rb

@@ -0,0 +1,28 @@
+module Prism
+  module Mailer
+    # Returned by a mailer action call (`UserMailer.welcome(user)`), in the
+    # spirit of ActionMailer's MessageDelivery: the message is already
+    # rendered at this point, #deliver_now hands it to Prism::Mailer.deliver!
+    # immediately, #deliver_later re-enqueues the action itself (mailer
+    # class, action name, args) as a Prism::Jobs::Job so a Worker performs
+    # the rendering and delivery out of process.
+    class Delivery
+      def initialize(message, mailer_class:, action_name:, args:)
+        @message = message
+        @mailer_class = mailer_class
+        @action_name = action_name
+        @args = args
+      end
+
+      attr_reader :message
+
+      def deliver_now
+        Mailer.deliver!(message)
+      end
+
+      def deliver_later(queue: nil, run_at: nil)
+        DeliveryJob.perform_later(@mailer_class.name, @action_name, @args, queue: queue, run_at: run_at)
+      end
+    end
+  end
+end

lib/prism/mailer/delivery_job.rb

@@ -0,0 +1,16 @@
+module Prism
+  module Mailer
+    # Performs a mailer action out of process. Enqueued by
+    # Delivery#deliver_later with the mailer class name (resolved back
+    # through Object.const_get, same pattern Jobs::Worker already uses for
+    # job classes) so the queue only ever persists plain strings/arrays.
+    class DeliveryJob < Prism::Jobs::Job
+      queue_as 'mailers'
+
+      def perform(mailer_class_name, action_name, args)
+        mailer_class = Object.const_get(mailer_class_name)
+        mailer_class.public_send(action_name, *args).deliver_now
+      end
+    end
+  end
+end