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Diator is a Python library for implementing CQRS pattern in your Python applications.

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![Diator Logo](https://github.com/akhundMurad/diator/blob/main/assets/logo_diator.svg?raw=true)

# Diator - CQRS Library for Python
**[Docs](https://akhundmurad.github.io/diator/) | [PyPI](https://pypi.org/project/diator/)**

Diator is a Python library for implementing CQRS pattern in your Python applications. It provides a set of abstractions and utilities to help you separate your read and write concerns, allowing for better scalability, performance, and maintainability of your application.

## Features :bulb:

- Implements the CQRS pattern.
- Simple, yet flexible API.
- Supports multiple message brokers, such as [Redis Pub/Sub](https://redis.io/docs/manual/pubsub/) and [Azure Service Bus](https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-messaging-overview).
- Supports various di-frameworks, such as [di](https://github.com/adriangb/di) and [rodi](https://github.com/Neoteroi/rodi).
- Easy to integrate with existing codebases.

## Installation :triangular_ruler:

Install the Diator library with [pip](https://pypi.org/project/diator/)

```bash
pip install diator
```

There are also several installation options:

- To use Redis as Message Broker

```bash
    pip install diator[redis]
    ```

- Or Azure Service Bus

```bash
    pip install diator[azure]
    ```

## Simple Example :hammer_and_wrench:

Minimal example of diator usage:

```python
import asyncio
from dataclasses import dataclass, field
from di import Container, bind_by_type
from di.dependent import Dependent
from diator.events import EventMap, Event, EventEmitter
from diator.container.di import DIContainer
from diator.mediator import Mediator
from diator.requests import Request, RequestHandler, RequestMap

@dataclass(frozen=True, kw_only=True)
class JoinMeetingCommand(Request):
    meeting_id: int
    user_id: int
    is_late: bool = field(default=False)

class JoinMeetingCommandHandler(RequestHandler[JoinMeetingCommand, None]):
    def __init__(self, meeting_api) -> None:
        self._meeting_api = meeting_api
        self._events: list[Event] = []

@property
    def events(self) -> list[Event]:
        return self._events

async def handle(self, request: JoinMeetingCommand) -> None:
        self._meeting_api.join(request.meeting_id, request.user_id)
        if request.is_late:
            self._meeting_api.warn(request.user_id)

def setup_di() -> DIContainer:
    external_container = Container()

external_container.bind(
        bind_by_type(
            Dependent(JoinMeetingCommandHandler, scope="request"),
            JoinMeetingCommandHandler,
        )
    )

container = DIContainer()
    container.attach_external_container(external_container)

return container

async def main() -> None:
    container = setup_di()

request_map = RequestMap()
    request_map.bind(JoinMeetingCommand, JoinMeetingCommandHandler)

event_emitter = EventEmitter(
        event_map=EventMap(), container=container, message_broker=None
    )

mediator = Mediator(
        request_map=request_map,
        event_emitter=event_emitter,
        container=container,
    )

await mediator.send(JoinMeetingCommand(user_id=1, meeting_id=1, is_late=True))

if __name__ == "__main__":
    asyncio.run(main())

```

## Further reading :scroll:

- [Udi Dahan - Clarified CQRS](https://udidahan.com/2009/12/09/clarified-cqrs/)
- [Martin Fowler - CQRS](https://martinfowler.com/bliki/CQRS.html)
- [Marting Fowler - What do you mean by “Event-Driven”?](https://martinfowler.com/articles/201701-event-driven.html)
- [Vlad Khononov - Learning Domain-Driven Design](https://www.oreilly.com/library/view/learning-domain-driven-design/9781098100124/)
- [Vaughn Vernon - Really Simple CQRS](https://kalele.io/really-simple-cqrs/)

## License

This project is licensed under the terms of the MIT license.

diator

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