"""请求级关联标识中间件。"""

import re
import uuid

from .logging import request_id_context

REQUEST_ID_PATTERN = re.compile(r"^[A-Za-z0-9._-]{1,64}$")


class RequestContextMiddleware:
    """复用合法入站标识或生成新标识，并确保上下文在请求结束后复位。"""

    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        incoming = request.headers.get("X-Request-ID", "")
        request_id = incoming if REQUEST_ID_PATTERN.fullmatch(incoming) else uuid.uuid4().hex
        token = request_id_context.set(request_id)
        request.request_id = request_id
        try:
            response = self.get_response(request)
            response["X-Request-ID"] = request_id
            return response
        finally:
            request_id_context.reset(token)