from django.shortcuts import resolve_url
from django.core.signing import Signer
from django.core.exceptions import SuspiciousOperation

signer = Signer()

import logging
logger = logging.getLogger(__name__)

def sign_data(data, l=None):
    sig = signer.sign(data)
    p = len(data) + 1
    if l:
        l += p
    return sig[p:l]

def signed_url(name, **kwargs):
    """
    >>> signed_url('foo/bar')
    """
    url = resolve_url(name, **kwargs)
    sig = signer.sign(url)
    sep = "&" if "?" in url else "?"
    return sig.replace(":", f"{sep}auth=")

def check_signed_url(full_path):
    p = full_path.rfind('auth')
    url = full_path[:p-1]
    logger.debug("check_signed_url: %s", url)
    signed = signed_url(url)
    if signed != full_path:
        logger.debug("Mismatch: %s != %s", full_path, signed)
        signed = "_HIDDEN_"
        raise SuspiciousOperation("Bad auth code")
    
if __name__ == '__main__':
    import doctest
    print(doctest.testmod())