"""Middleware to propagate or generate request_id for every request."""

import uuid

from starlette.middleware.base import BaseHTTPMiddleware
from starlette.requests import Request
from starlette.responses import Response

from app.core.logging_config import request_id_ctx

REQUEST_ID_HEADER = "X-Request-ID"


class RequestIDMiddleware(BaseHTTPMiddleware):
    """Extract X-Request-ID from incoming request headers or generate one.

    The request_id is stored in a ContextVar so that all log records emitted
    during the request are automatically annotated with it, without needing to
    pass it explicitly through every call.

    The same request_id is also echoed back in the response header so that
    callers can correlate logs.
    """

    async def dispatch(self, request: Request, call_next) -> Response:
        request_id = request.headers.get(REQUEST_ID_HEADER) or str(uuid.uuid4())
        token = request_id_ctx.set(request_id)
        try:
            response = await call_next(request)
        finally:
            request_id_ctx.reset(token)

        response.headers[REQUEST_ID_HEADER] = request_id
        return response