import json
import hmac
import hashlib
import time
from typing import Any, Dict
from .errors import BadRequestError


class WebhooksClient:
    """
    A client to handle ElevenLabs webhook-related functionality
    """

    def construct_event(self, rawBody: str, sig_header: str, secret: str) -> Dict:
        """
        Constructs a webhook event object from a payload and signature.
        Verifies the webhook signature to ensure the event came from ElevenLabs.

        Args:
            rawBody: The webhook request body. Must be the raw body, not a JSON object
            sig_header: The signature header from the request
            secret: Your webhook secret

        Returns:
            The verified webhook event

        Raises:
            BadRequestError: If the signature is invalid or missing
        """

        if not sig_header:
            raise BadRequestError(body="Missing signature header")

        if not secret:
            raise BadRequestError(body="Webhook secret not configured")

        headers = sig_header.split(',')
        timestamp = None
        signature = None

        for header in headers:
            if header.startswith('t='):
                timestamp = header[2:]
            elif header.startswith('v0='):
                signature = header

        if not timestamp or not signature:
            raise BadRequestError(body="No signature hash found with expected scheme v0")

        # Validate timestamp
        req_timestamp = int(timestamp) * 1000
        tolerance = int(time.time() * 1000) - 30 * 60 * 1000
        if req_timestamp < tolerance:
            raise BadRequestError(body="Timestamp outside the tolerance zone")

        # Validate hash
        message = f"{timestamp}.{rawBody}"

        digest = "v0=" + hmac.new(
            secret.encode('utf-8'),
            message.encode('utf-8'),
            hashlib.sha256
        ).hexdigest()

        if signature != digest:
            raise BadRequestError(
                body="Signature hash does not match the expected signature hash for payload"
            )

        return json.loads(rawBody)