Marker interface for anything that can travel through the bus. Command\CommandInterface and Query\QueryInterface both extend it; ResultInterface also extends it so a result can itself be passed to the terminal handler in the pipeline.

MessageBusInterface extends PipelineHandlerInterface and is the public entry point of the library. Call handle(MessageInterface $message): ResultInterface to dispatch a command or query.

MessageBus is the default implementation. It's a thin, final readonly wrapper that delegates directly to a MiddlewarePipelineInterface instance.

The pipeline continuation contract: handle(MessageInterface $message): ResultInterface. Implemented by MessageBusInterface, MiddlewarePipelineInterface, Next, and Handler\EmptyPipelineHandler. It names the rest of the pipeline that a middleware hands control to, and is what MiddlewareInterface::process() receives as its second argument.

The common supertype for all resolved handlers. CommandHandlerInterface and QueryHandlerInterface both extend it, so a single type covers every handler the resolver can return.

Marker interfaces for application-defined command and query handlers. Each extends MessageHandlerInterface and declares no method: the wired StrategyInterface chooses which method is called (see Strategy).

Given a message, looks up its mapped handler class in the command_map/query_map configuration (see Configuration) and fetches it from the PSR-11 container.

Returns MessageHandlerInterface. Throws Exception\InvalidConfigurationException if the message's class has no map entry or the resolved handler is not an instance of the expected marker, and Exception\ServiceNotFoundException if the config service or the mapped handler class isn't registered in the container.

ResultInterface extends MessageInterface and exposes getResult(): mixed and getStatus(): StatusInterface, letting a handler's result be sent back through the pipeline as a message. Command\CommandResult and Query\QueryResult (see Commands & Queries) are the concrete implementations.

StatusInterface is an empty marker; MessageStatus is the built-in enum implementing it, with Success and Failure cases.