refactor: refactors message dequeueing (#2810)

app/lib/message_dequeuer/single_message_processor.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+module MessageDequeuer
+  class SingleMessageProcessor < Base
+
+    def process
+      catch_stops do
+        check_message_exists
+        check_server_suspension
+        check_delivery_attempts
+        check_raw_message_exists
+
+        processor = nil
+        case queued_message.message.scope
+        when "incoming"
+          processor = IncomingMessageProcessor
+        when "outgoing"
+          processor = OutgoingMessageProcessor
+        else
+          create_delivery "HardFail", details: "Scope #{queued_message.message.scope} is not valid"
+          remove_from_queue
+          stop_processing
+        end
+
+        processor.process(queued_message, logger: @logger, state: @state)
+      end
+    rescue StandardError => e
+      handle_exception(e)
+    end
+
+    private
+
+    def check_message_exists
+      queued_message.message
+    rescue Postal::MessageDB::Message::NotFound
+      log "unqueueing because backend message has been removed"
+      remove_from_queue
+      stop_processing
+    end
+
+    def check_server_suspension
+      return unless queued_message.server.suspended?
+
+      log "server is suspended, holding message"
+      create_delivery "Held", details: "Mail server has been suspended. No e-mails can be processed at present. Contact support for assistance."
+      remove_from_queue
+      stop_processing
+    end
+
+    def check_delivery_attempts
+      return if queued_message.attempts < Postal.config.general.maximum_delivery_attempts
+
+      details = "Maximum number of delivery attempts (#{queued_message.attempts}) has been reached."
+      if queued_message.message.scope == "incoming"
+        # Send bounces to incoming e-mails when they are hard failed
+        if bounce_id = queued_message.send_bounce
+          details += " Bounce sent to sender (see message <msg:#{bounce_id}>)"
+        end
+      elsif queued_message.message.scope == "outgoing"
+        # Add the recipient to the suppression list
+        if queued_message.server.message_db.suppression_list.add(:recipient, queued_message.message.rcpt_to, reason: "too many soft fails")
+          log "added #{queued_message.message.rcpt_to} to suppression list because maximum attempts has been reached"
+          details += " Added #{queued_message.message.rcpt_to} to suppression list because delivery has failed #{queued_message.attempts} times."
+        end
+      end
+
+      log "message has reached maximum number of attempts, hard failing"
+      create_delivery "HardFail", details: details
+      remove_from_queue
+      stop_processing
+    end
+
+    def check_raw_message_exists
+      return if queued_message.message.raw_message?
+
+      log "raw message has been removed, not sending"
+      create_delivery "HardFail", details: "Raw message has been removed. Cannot send message."
+      remove_from_queue
+      stop_processing
+    end
+
+  end
+end