Welcome message sent when a client is registered

This introduces new components:

1. Communication BC (packaged as a gem)
2. Read model for displaying inbox

One new process manager:

- welcome message process

The Communication BC input is only SendMessage command and the output is MessageSent event.
The BC and the process manager have their own unit tests.
The UI is tested via integration test. In the future we will introduce unit tests for the read model.

Author: andrzejkrzywda

ecommerce/communication/.mutant.yml

@@ -0,0 +1,12 @@
+requires:
+  - ./test/test_helper
+integration: minitest
+usage: opensource
+coverage_criteria:
+  process_abort: true
+matcher:
+  subjects:
+    - Communication*
+  ignore:
+    - Communication::Configuration#call
+

ecommerce/communication/Gemfile

@@ -0,0 +1,4 @@
+source "https://rubygems.org"
+
+eval_gemfile "../../infra/Gemfile.test"
+gem "infra", path: "../../infra"

ecommerce/communication/Gemfile.lock

@@ -0,0 +1,106 @@
+PATH
+  remote: ../../infra
+  specs:
+    infra (1.0.0)
+      aggregate_root (~> 2.15)
+      arkency-command_bus
+      dry-struct
+      dry-types
+      rake
+      ruby_event_store (~> 2.15)
+      ruby_event_store-transformations
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    activesupport (8.0.2)
+      base64
+      benchmark (>= 0.3)
+      bigdecimal
+      concurrent-ruby (~> 1.0, >= 1.3.1)
+      connection_pool (>= 2.2.5)
+      drb
+      i18n (>= 1.6, < 2)
+      logger (>= 1.4.2)
+      minitest (>= 5.1)
+      securerandom (>= 0.3)
+      tzinfo (~> 2.0, >= 2.0.5)
+      uri (>= 0.13.1)
+    aggregate_root (2.16.0)
+      ruby_event_store (= 2.16.0)
+    arkency-command_bus (0.4.1)
+      concurrent-ruby
+    ast (2.4.2)
+    base64 (0.2.0)
+    benchmark (0.4.0)
+    bigdecimal (3.1.9)
+    concurrent-ruby (1.3.5)
+    connection_pool (2.5.0)
+    diff-lcs (1.5.1)
+    drb (2.2.1)
+    dry-core (1.0.1)
+      concurrent-ruby (~> 1.0)
+      zeitwerk (~> 2.6)
+    dry-inflector (1.0.0)
+    dry-logic (1.5.0)
+      concurrent-ruby (~> 1.0)
+      dry-core (~> 1.0, < 2)
+      zeitwerk (~> 2.6)
+    dry-struct (1.6.0)
+      dry-core (~> 1.0, < 2)
+      dry-types (>= 1.7, < 2)
+      ice_nine (~> 0.11)
+      zeitwerk (~> 2.6)
+    dry-types (1.7.2)
+      bigdecimal (~> 3.0)
+      concurrent-ruby (~> 1.0)
+      dry-core (~> 1.0)
+      dry-inflector (~> 1.0)
+      dry-logic (~> 1.4)
+      zeitwerk (~> 2.6)
+    i18n (1.14.7)
+      concurrent-ruby (~> 1.0)
+    ice_nine (0.11.2)
+    logger (1.6.6)
+    minitest (5.25.0)
+    mutant (0.12.4)
+      diff-lcs (~> 1.3)
+      parser (~> 3.3.0)
+      regexp_parser (~> 2.9.0)
+      sorbet-runtime (~> 0.5.0)
+      unparser (~> 0.6.14)
+    mutant-minitest (0.12.4)
+      minitest (~> 5.11)
+      mutant (= 0.12.4)
+    parser (3.3.4.2)
+      ast (~> 2.4.1)
+      racc
+    racc (1.8.1)
+    rake (13.2.1)
+    regexp_parser (2.9.2)
+    ruby_event_store (2.16.0)
+      concurrent-ruby (~> 1.0, >= 1.1.6)
+    ruby_event_store-transformations (0.1.0)
+      activesupport (>= 5.0)
+      ruby_event_store (>= 2.0.0, < 3.0.0)
+    securerandom (0.4.1)
+    sorbet-runtime (0.5.11525)
+    tzinfo (2.0.6)
+      concurrent-ruby (~> 1.0)
+    unparser (0.6.15)
+      diff-lcs (~> 1.3)
+      parser (>= 3.3.0)
+    uri (0.13.1)
+    zeitwerk (2.7.2)
+
+PLATFORMS
+  arm64-darwin-24
+  ruby
+
+DEPENDENCIES
+  infra!
+  minitest (= 5.25.0)!
+  mutant-minitest (= 0.12.4)!
+
+BUNDLED WITH
+   2.6.6

ecommerce/communication/Makefile

@@ -0,0 +1,10 @@
+install:
+	@bundle install
+
+test:
+	@bundle exec ruby -e "require \"rake/rake_test_loader\"" test/*_test.rb
+
+mutate:
+	@RAILS_ENV=test bundle exec mutant run
+
+.PHONY: install test mutate

ecommerce/communication/README.md

@@ -0,0 +1,26 @@
+# Communication Module
+
+This module handles communication-related logic for the ecommerce platform.
+
+## Structure
+
+- `lib/` - Main source code for the communication domain
+- `test/` - Unit tests for the communication domain
+
+## Development
+
+- Install dependencies: `bundle install`
+- Run tests: `make test`
+
+## Testing
+
+Tests are located in the `test/` directory. Use the provided Makefile to run them.
+
+## Mutation Testing
+
+Mutation testing is configured via `.mutant.yml`.
+
+---
+
+For more details on the architecture and DDD approach, see the main [README](../../README.md).
+

ecommerce/communication/lib/communication.rb

@@ -0,0 +1,55 @@
+require "infra"
+
+module Communication
+  class Configuration
+
+    def call(event_store, command_bus)
+      command_bus.register(SendMessage, OnSendMessage.new(event_store))
+    end
+  end
+
+  class SendMessage < Infra::Command
+    attribute :message_id, Infra::Types::UUID
+    attribute :receiver_id, Infra::Types::UUID
+    attribute :message, Infra::Types::String
+  end
+
+  class MessageSent < Infra::Event
+    attribute :message_id, Infra::Types::UUID
+    attribute :receiver_id, Infra::Types::UUID
+    attribute :message, Infra::Types::String
+  end
+
+  class OnSendMessage
+    def initialize(event_store)
+      @repository = Infra::AggregateRootRepository.new(event_store)
+    end
+
+    def call(command)
+      @repository.with_aggregate(Message, command.message_id) do |message|
+        message._send(command.receiver_id, command.message)
+      end
+    end
+  end
+
+  class Message
+    include AggregateRoot
+
+    def initialize(id)
+      @id = id
+    end
+
+    def _send(receiver_id, message)
+      apply MessageSent.new(
+        data: {
+          message_id: @id,
+          receiver_id: receiver_id,
+          message: message
+        }
+      )
+    end
+
+    def apply_message_sent(_)
+    end
+  end
+end

ecommerce/communication/test/sending_message_test.rb

@@ -0,0 +1,15 @@
+require_relative "test_helper"
+
+module Communication
+  class SendingMessageTest < Test
+    cover "Communication*"
+
+    def test_happy_path
+      expected_event = MessageSent.new(data: {message_id: message_id, receiver_id: receiver_id, message: message_content})
+      assert_events("Communication::Message$#{message_id}", expected_event) do
+        send_message
+      end
+    end
+  end
+end
+

ecommerce/communication/test/test_helper.rb

@@ -0,0 +1,32 @@
+require "minitest/autorun"
+require "mutant/minitest/coverage"
+
+require_relative "../lib/communication"
+
+module Communication
+  class Test < Infra::InMemoryTest
+    def before_setup
+      super()
+      Configuration.new.call(event_store, command_bus)
+    end
+
+    private
+
+    def send_message
+      run_command(SendMessage.new(message_id: message_id, receiver_id: receiver_id, message: message_content))
+    end
+
+    def message_content
+      "Hello, this is a test message."
+    end
+
+    def receiver_id
+      @receiver_id ||= SecureRandom.uuid
+    end
+
+    def message_id
+      @message_id ||= SecureRandom.uuid
+    end
+
+  end
+end

ecommerce/configuration.rb

@@ -9,6 +9,8 @@
 require_relative "invoicing/lib/invoicing"
 require_relative "taxes/lib/taxes"
 require_relative "fulfillment/lib/fulfillment"
+require_relative "communication/lib/communication"
+require_relative "processes/lib/processes"
 
 module Ecommerce
   class Configuration
@@ -37,6 +39,7 @@ def configure_bounded_contexts(event_store, command_bus)
         Taxes::Configuration.new,
         ProductCatalog::Configuration.new,
         Fulfillment::Configuration.new(@number_generator),
+        Communication::Configuration.new,
       ].each { |c| c.call(event_store, command_bus) }
     end
   end

rails_application/app/processes/processes/welcome_message_process.rb

@@ -8,7 +8,12 @@ def initialize(event_store, command_bus)
     def call(event)
       case event
       when Crm::CustomerRegistered
-        ClientInbox::Message.create(client_uid: event.data.fetch(:customer_id), title: "Welcome to our platform!")
+        @command_bus.call(
+          Communication::SendMessage.new(
+            message_id: SecureRandom.uuid,
+            receiver_id: event.data.fetch(:customer_id),
+            message: "Welcome to our platform!")
+        )
       end
     end
   end