from logging import Logger
from typing import Any, Callable, Dict, Optional

from slack_sdk.signature import SignatureVerifier

from slack_bolt.logger import get_bolt_logger
from slack_bolt.middleware.middleware import Middleware
from slack_bolt.request import BoltRequest
from slack_bolt.response import BoltResponse


class RequestVerification(Middleware):
    def __init__(self, signing_secret: str, base_logger: Optional[Logger] = None):
        """Verifies an incoming request by checking the validity of
        `x-slack-signature`, `x-slack-request-timestamp`, and its body data.

        Refer to https://docs.slack.dev/authentication/verifying-requests-from-slack/ for details.

        Args:
            signing_secret: The signing secret
            base_logger: The base logger
        """
        self._signing_secret = signing_secret
        self._verifier: Optional[SignatureVerifier] = None
        self.logger = get_bolt_logger(RequestVerification, base_logger=base_logger)

    @property
    def verifier(self) -> SignatureVerifier:
        # Defer initialization to avoid errors during start up
        if self._verifier is None:
            self._verifier = SignatureVerifier(signing_secret=self._signing_secret)
        return self._verifier

    def process(
        self,
        *,
        req: BoltRequest,
        resp: BoltResponse,
        # As this method is not supposed to be invoked by bolt-python users,
        # the naming conflict with the built-in one affects
        # only the internals of this method
        next: Callable[[], BoltResponse],
    ) -> BoltResponse:
        if self._can_skip(req.mode, req.body):
            return next()

        body = req.raw_body
        timestamp = req.headers.get("x-slack-request-timestamp", ["0"])[0]
        signature = req.headers.get("x-slack-signature", [""])[0]
        if self.verifier.is_valid(body, timestamp, signature):
            return next()
        else:
            self._debug_log_error(signature, timestamp, body)
            return self._build_error_response()

    # -----------------------------------------

    @staticmethod
    def _can_skip(mode: str, body: Dict[str, Any]) -> bool:
        return mode == "socket_mode"

    @staticmethod
    def _build_error_response() -> BoltResponse:
        return BoltResponse(status=401, body={"error": "invalid request"})

    def _debug_log_error(self, signature, timestamp, body) -> None:
        self.logger.info(
            "Invalid request signature detected " f"(signature: {signature}, timestamp: {timestamp}, body: {body})"
        )