from flask import request
from utils.exceptions import Unauthorized


def get_auth_token():
    """Get access token from Authorization header.

    Returns:
        str: Authorization token.

    Raises:
        Unauthorized: If token is missing or invalid.

    """
    auth = request.headers.get("Authorization")
    if not auth:
        raise Unauthorized("Authorization header is expected.")

    parts = auth.split()

    if parts[0].lower() != "bearer":
        raise Unauthorized("Authorization header must contain a Bearer token.")
    elif len(parts) == 1:
        raise Unauthorized("Token is missing.")
    elif len(parts) > 2:
        raise Unauthorized("Invalid token.")

    return parts[1]