"""
Server-Sent Events (SSE) service using Redis pub/sub.
"""

from typing import AsyncGenerator
import json
import structlog
from redis.asyncio import Redis

from app.core.config import settings
from app.models.events import Event
from shared.redis_utils import get_redis_client

logger = structlog.get_logger()


class SSEService:
    """
    Manage real-time event streaming via Redis pub/sub.

    Pattern: alerts:{tenant_id}
    """

    def __init__(self, redis: Redis = None):
        self._redis = redis  # Use private attribute to allow lazy loading
        self.prefix = settings.REDIS_SSE_PREFIX

    @property
    async def redis(self) -> Redis:
        """
        Lazy load Redis client if not provided through dependency injection.
        Uses the shared Redis utilities for consistency.
        """
        if self._redis is None:
            self._redis = await get_redis_client()
        return self._redis

    async def publish_event(self, event: Event) -> bool:
        """
        Publish event to Redis for SSE streaming.

        Args:
            event: Event to publish

        Returns:
            True if published successfully
        """
        try:
            redis_client = await self.redis

            # Build channel name
            channel = f"{self.prefix}:{event.tenant_id}"

            # Build message payload
            payload = {
                "id": str(event.id),
                "tenant_id": str(event.tenant_id),
                "event_class": event.event_class,
                "event_domain": event.event_domain,
                "event_type": event.event_type,
                "priority_score": event.priority_score,
                "priority_level": event.priority_level,
                "type_class": event.type_class,
                "status": event.status,
                "created_at": event.created_at.isoformat(),
                "i18n": {
                    "title_key": event.i18n_title_key,
                    "title_params": event.i18n_title_params,
                    "message_key": event.i18n_message_key,
                    "message_params": event.i18n_message_params
                },
                "smart_actions": event.smart_actions,
                "entity_links": event.entity_links
            }

            # Publish to Redis
            await redis_client.publish(channel, json.dumps(payload))

            logger.debug(
                "sse_event_published",
                channel=channel,
                event_type=event.event_type,
                event_id=str(event.id)
            )

            return True

        except Exception as e:
            logger.error(
                "sse_publish_failed",
                error=str(e),
                event_id=str(event.id)
            )
            return False

    async def subscribe_to_tenant(
        self,
        tenant_id: str
    ) -> AsyncGenerator[str, None]:
        """
        Subscribe to tenant's alert stream.

        Args:
            tenant_id: Tenant UUID

        Yields:
            JSON-encoded event messages
        """
        redis_client = await self.redis
        channel = f"{self.prefix}:{tenant_id}"

        logger.info("sse_subscription_started", channel=channel)

        # Subscribe to Redis channel
        pubsub = redis_client.pubsub()
        await pubsub.subscribe(channel)

        try:
            async for message in pubsub.listen():
                if message["type"] == "message":
                    yield message["data"]

        except Exception as e:
            logger.error("sse_subscription_error", error=str(e), channel=channel)
            raise
        finally:
            await pubsub.unsubscribe(channel)
            await pubsub.close()
            logger.info("sse_subscription_closed", channel=channel)