"""Factory functions for creating event publishers and subscribers."""

import os
from enum import Enum

from .base import EventPublisher, EventSubscriber
from .redis_pubsub import RedisPubSubPublisher, RedisPubSubSubscriber


class EventBackend(str, Enum):
    """Supported event backends."""

    REDIS_PUBSUB = "redis_pubsub"
    REDIS_STREAMS = "redis_streams"  # Future
    KAFKA = "kafka"  # Future


def get_publisher(
    backend: EventBackend | str | None = None,
    source: str = "",
    **kwargs,
) -> EventPublisher:
    """
    Factory function to get an event publisher.

    Args:
        backend: The event backend to use (default: from EVENTS_BACKEND env var or redis_pubsub)
        source: Identifier for the source service
        **kwargs: Backend-specific options

    Returns:
        An EventPublisher instance

    Environment variables:
        EVENTS_BACKEND: Default backend (redis_pubsub, redis_streams, kafka)
        REDIS_URL: Redis connection URL
        KAFKA_BOOTSTRAP_SERVERS: Kafka bootstrap servers (future)
    """
    if backend is None:
        backend = os.getenv("EVENTS_BACKEND", EventBackend.REDIS_PUBSUB)

    if isinstance(backend, str):
        backend = EventBackend(backend)

    if backend == EventBackend.REDIS_PUBSUB:
        redis_url = kwargs.get("redis_url") or os.getenv(
            "REDIS_URL", "redis://localhost:6379"
        )
        return RedisPubSubPublisher(redis_url=redis_url, source=source)

    elif backend == EventBackend.REDIS_STREAMS:
        raise NotImplementedError("Redis Streams backend not yet implemented")

    elif backend == EventBackend.KAFKA:
        raise NotImplementedError("Kafka backend not yet implemented")

    else:
        raise ValueError(f"Unknown event backend: {backend}")


def get_subscriber(
    topics: list[str] | None = None,
    backend: EventBackend | str | None = None,
    **kwargs,
) -> EventSubscriber:
    """
    Factory function to get an event subscriber.

    Args:
        topics: Topics to subscribe to
        backend: The event backend to use (default: from EVENTS_BACKEND env var or redis_pubsub)
        **kwargs: Backend-specific options

    Returns:
        An EventSubscriber instance

    Environment variables:
        EVENTS_BACKEND: Default backend (redis_pubsub, redis_streams, kafka)
        REDIS_URL: Redis connection URL
        KAFKA_BOOTSTRAP_SERVERS: Kafka bootstrap servers (future)
    """
    if backend is None:
        backend = os.getenv("EVENTS_BACKEND", EventBackend.REDIS_PUBSUB)

    if isinstance(backend, str):
        backend = EventBackend(backend)

    if backend == EventBackend.REDIS_PUBSUB:
        redis_url = kwargs.get("redis_url") or os.getenv(
            "REDIS_URL", "redis://localhost:6379"
        )
        return RedisPubSubSubscriber(redis_url=redis_url, topics=topics)

    elif backend == EventBackend.REDIS_STREAMS:
        raise NotImplementedError("Redis Streams backend not yet implemented")

    elif backend == EventBackend.KAFKA:
        raise NotImplementedError("Kafka backend not yet implemented")

    else:
        raise ValueError(f"Unknown event backend: {backend}")