File & directory structure for Apparat modules (DDD)

.
|-- composer.json
|-- src
|   `-- <PACKAGE>
|       |-- Application
|       |   |-- CommandHandlers
|       |   `-- Service
|       |-- Domain
|       |   |-- Command
|       |   |   |-- CommandBusInterface.php
|       |   |   `-- CommandHandlerInterface.php
|       |   |-- Model
|       |   |   |-- Entity.php
|       |   |   `-- EntityRepository.php (Interface)
|       |   |-- ValueObject.php
|       |   `-- DTO.php
|       `-- Framework
|           |-- Http¹
|           `-- Persistence²
`-- tests

¹ Arbitrary number of primary ports (may e.g. be Api, Cli, Rest, etc.)

² Arbitrary number of secondary ports

Namespaces

`Domain`

Defining the behaviour and constraints of the application
Business logic ("Core domain")
- Entities
- Value objects
- Validators
- Specifications
Supporting domain logic
- Domain services
  - Representing, orchestrating and executing domain tasks and operations
  - Stateless
- Domain Events
- Use-Cases / Commands (definitions of what actions an be taken on the applications)
Framework agnostic / infrastructure independent
Providing interfaces ("ports") for implementations ("adapters"), e.g. a repository interface
No external dependencies³
Must be run from the Application namespace
Only domain logic changes should ever affect this namespace

³ Dependencies to 3rd-party libraries might be OK under certain circumstances:

If it's something that you would write in your own domain code, and that would make sense to extract into some reusable code, and that can be extracted into a reusable library, then you might as well depend on a library that does the same thing, but that happens to have been written by someone else.

`Application`

Main entry point
Orchestrates the use of Domain layer entities
Adapts requests from the Framework layer to the Domain layer
Handles use-cases / commands
Dispatches domain events raised by the Domain layer
Primary point of integration
- Application level configuration
- Dependency injection configuration
- Abstract base classes
  - Providing shared functionality
  - No domain or port logic
  - To be extended by domain or port classes, e.g.
    - Entity base class (Domain)
    - Controller base (Ports)
- Application services
  - Middleware between the outside world and the domain logic
  - Transforming commands from the outside to domain instructions
  - Possibly having dependencies (e.g. Framework)
  - Communication using DTOs (Data Transfer Objects)
- Service providers
  - Translating primary port signals (HTTP, API, Cli, REST, etc.) to domain service calls
  - Connecting the domain with the infrastructure (binding secondary adapters to domain interfaces)

`Framework`

Integration of 3rd-party libraries (e.g. everything composer pulls in)
Adapts requests from the outside world to the Application layer
- Accepting HTTP requests
- Collecting user data
- Routing to a Controller etc.
- Calling an application use-case, passing on user data and make the Application layer handle the use-case
Implementing Application interfaces
Primary Ports / "Driving" Adapters
- Connecting the application to "The Outer World"
- Controllers / MVC implementations
- e.g. Http / Api / Cli / Rest ...
Secondary Ports / "Driven" Adapters
- Connecting the application to the local infrastructure
- Storage, databases (e.g. repository implementations), etc.

Structure before DDD reorganization:

.
|-- README.md
|-- composer.json
|-- phpunit.php
|-- phpunit.xml.dist
|-- src
|   |-- Resource
|   |   |-- ExceptionInterface.php
|   |   |-- File
|   |   |   |-- CommonMark.php
|   |   |   |-- Exception
|   |   |   |   |-- InvalidArgument.php
|   |   |   |   `-- Runtime.php
|   |   |   |-- ExceptionInterface.php
|   |   |   |-- Frontmatter
|   |   |   |   `-- Yaml
|   |   |   |       |-- CommonMark.php
|   |   |   |       `-- Exception
|   |   |   |           `-- InvalidArgument.php
|   |   |   |-- FrontmatterInterface.php
|   |   |   |-- Generic.php
|   |   |   |-- Part
|   |   |   |   |-- Body
|   |   |   |   |   |-- CommonMark.php
|   |   |   |   |   |-- Exception
|   |   |   |   |   |   `-- OutOfBounds.php
|   |   |   |   |   |-- ExceptionInterface.php
|   |   |   |   |   |-- Generic.php
|   |   |   |   |   |-- Text.php
|   |   |   |   |   `-- Yaml.php
|   |   |   |   |-- Body.php
|   |   |   |   |-- BodyInterface.php
|   |   |   |   |-- Container
|   |   |   |   |   |-- Choice.php
|   |   |   |   |   |-- ChoiceInterface.php
|   |   |   |   |   |-- Exception
|   |   |   |   |   |   |-- InvalidArgument.php
|   |   |   |   |   |   |-- OutOfBounds.php
|   |   |   |   |   |   |-- OutOfRange.php
|   |   |   |   |   |   `-- Runtime.php
|   |   |   |   |   |-- ExceptionInterface.php
|   |   |   |   |   |-- Sequence.php
|   |   |   |   |   `-- SequenceInterface.php
|   |   |   |   |-- Container.php
|   |   |   |   |-- ContainerInterface.php
|   |   |   |   `-- ContainerTrait.php
|   |   |   |-- Part.php
|   |   |   |-- PartInterface.php
|   |   |   |-- Text.php
|   |   |   `-- Yaml.php
|   |   |-- File.php
|   |   |-- FileInterface.php
|   |   `-- Utility.php
|   |-- Resource.php
|   `-- ResourceInterface.php
`-- test
    |-- CommonMarkTest.php
    |-- FileTest.php
    |-- FrontMarkTest.php
    |-- TestBase.php
    |-- TextTest.php
    |-- YamlTest.php
    `-- files
        |-- cc0++.txt
        |-- cc0.txt
        |-- commonmark.md
        |-- frontmark.md
        |-- invoice.php
        `-- invoice.yaml