"""
Server-Sent Events (SSE) API endpoint.
"""

from fastapi import APIRouter, HTTPException
from fastapi.responses import StreamingResponse
from uuid import UUID
from redis.asyncio import Redis
import structlog

from shared.redis_utils import get_redis_client
from app.services.sse_service import SSEService

logger = structlog.get_logger()

router = APIRouter()


@router.get("/sse/alerts/{tenant_id}")
async def stream_alerts(tenant_id: UUID):
    """
    Stream real-time alerts via Server-Sent Events (SSE).

    Usage (frontend):
    ```javascript
    const eventSource = new EventSource('/api/v1/sse/alerts/{tenant_id}');
    eventSource.onmessage = (event) => {
        const alert = JSON.parse(event.data);
        console.log('New alert:', alert);
    };
    ```

    Response format:
    ```
    data: {"id": "...", "event_type": "...", ...}

    data: {"id": "...", "event_type": "...", ...}

    ```
    """
    # Get Redis client from shared utilities
    redis = await get_redis_client()
    try:
        sse_service = SSEService(redis)

        async def event_generator():
            """Generator for SSE stream"""
            try:
                async for message in sse_service.subscribe_to_tenant(str(tenant_id)):
                    # Format as SSE message
                    yield f"data: {message}\n\n"

            except Exception as e:
                logger.error("sse_stream_error", error=str(e), tenant_id=str(tenant_id))
                # Send error message and close
                yield f"event: error\ndata: {str(e)}\n\n"

        return StreamingResponse(
            event_generator(),
            media_type="text/event-stream",
            headers={
                "Cache-Control": "no-cache",
                "Connection": "keep-alive",
                "X-Accel-Buffering": "no"  # Disable nginx buffering
            }
        )

    except Exception as e:
        logger.error("sse_setup_failed", error=str(e), tenant_id=str(tenant_id))
        raise HTTPException(status_code=500, detail="Failed to setup SSE stream")