"""
SSE endpoint — clients connect here to receive live task progress.

GET /api/v1/events?task_id=<uuid>

The connection stays open; the server pushes events as the task runs.
Nginx must have `proxy_buffering off` for this to work through a reverse proxy.
"""

import asyncio

from fastapi import APIRouter, Depends, Request
from fastapi.responses import StreamingResponse

from app.dependencies import get_current_user
from app.models.user import User
from app.services.sse import sse_manager

router = APIRouter(prefix="/api/v1/events", tags=["events"])


@router.get("")
async def event_stream(
    request: Request,
    task_id: str,
    _: User = Depends(get_current_user),
):
    queue: asyncio.Queue = asyncio.Queue(maxsize=200)
    await sse_manager.subscribe(task_id, queue)

    async def generator():
        try:
            while True:
                if await request.is_disconnected():
                    break
                try:
                    event = await asyncio.wait_for(queue.get(), timeout=25.0)
                    yield event.encode()
                except asyncio.TimeoutError:
                    yield ": keepalive\n\n"
        finally:
            await sse_manager.unsubscribe(task_id, queue)

    return StreamingResponse(
        generator(),
        media_type="text/event-stream",
        headers={
            "Cache-Control": "no-cache",
            "X-Accel-Buffering": "no",   # tells Nginx to disable buffering
            "Connection": "keep-alive",
        },
    )