app/api/notes/notes_events.py

import asyncio
import json
import logging
from fastapi import APIRouter
from sse_starlette.sse import EventSourceResponse

from app.services.note_store import get_note
from app.models.enums import NoteStatus

logger = logging.getLogger(__name__)

router = APIRouter()

@router.get("/notes/{note_id}/events")
async def note_events(note_id: str):
    """
    Server-Sent Events endpoint:
    - Push note.status whenever it changes
    - Close stream when status == ready or error
    """

    async def event_generator():
        last_status = None

        try:
            while True:
                note = get_note(note_id)

                if not note:
                    # note chưa được tạo, chờ
                    await asyncio.sleep(0.5)
                    continue

                status = note.get("status")

                # Push only when status changes
                if status != last_status:
                    yield {
                        "event": "status",
                        "data": json.dumps({
                            "note_id": note_id,
                            "status": status,
                        }),
                    }
                    last_status = status

                # Terminal states → close SSE
                if status in (
                    NoteStatus.ready,
                    NoteStatus.error,
                ):
                    break

                # Avoid hammering Firestore
                await asyncio.sleep(1.0)

        except asyncio.CancelledError:
            # Client disconnected (normal)
            logger.info(
                "[notes_events] SSE client disconnected note_id=%s",
                note_id,
            )
        except Exception as e:
            logger.exception(
                "[notes_events] SSE error note_id=%s: %s",
                note_id,
                e,
            )
            yield {
                "event": "error",
                "data": json.dumps({
                    "note_id": note_id,
                    "status": "internal_error",
                }),
            }

    return EventSourceResponse(
        event_generator(),
        ping=15,   # keep-alive, tránh proxy/nginx kill connection
    )