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 final handler in the pipeline.

MessageBusInterface extends MessageHandlerInterface 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 common contract implemented by anything capable of handling a message: MessageBusInterface, CommandHandlerInterface, QueryHandlerInterface, middleware pipelines, and the internal Next/ EmptyPipelineHandler classes all implement this single handle() method.

Marker interfaces for application-defined command and query handlers. Both simply re-declare handle(MessageInterface $message): ResultInterface for clarity/type-narrowing at the edges of an application; there is no behavioral difference between the two beyond intent.

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.

Throws Exception\InvalidConfigurationException if the message's class has no map entry, and Exception\ServiceNotFoundException if 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 used by this library.

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