import hmac
import hashlib
import base64


class ImgProxy:
    """
    The class generates a signature for the imgproxy (https://github.com/DarthSim/imgproxy).

    Author: Yehor Smoliakov (https://github.com/egorsmkv)
    """

    def __init__(self, key, salt):
        self._key = bytes.fromhex(key)
        self._salt = bytes.fromhex(salt)

    def generate(self, url, resize, width, height, gravity, enlarge, extension):
        b64_url = base64.urlsafe_b64encode(str.encode(url)).rstrip(b'=').decode()

        path = f'/{resize}/{width}/{height}/{gravity}/{enlarge}/{b64_url}.{extension}'

        sha256_hmac = hmac.new(self._key, self._salt + str.encode(path), digestmod=hashlib.sha256)

        protection = base64.urlsafe_b64encode(sha256_hmac.digest()).rstrip(b'=').decode()

        return f'/{protection}{path}'


if __name__ == '__main__':
    test_key = 'ed7688b54dfaefecddcad524334cdf429983a11c728016f8032bb6ae033c790de5b547f819e23a2abd37fb3971e4c1323855503545a0e6b783db820c2ac18826'
    test_salt = '5217a47ea8ad2b2e74695e8e4b344514d631e6882575f376ee59393dbd31757fe41adb2919a1e4fffd3fec9d410d34ccada8df6ac3e3d4e6b07bf73f2f2a0cad'

    test_url = 'https://avatars3.githubusercontent.com/u/41049275?s=460&v=4'
    test_resize = 'fill'
    test_width = 10
    test_height = 10
    test_gravity = 'no'
    test_enlarge = 1
    test_extension = 'png'

    imp = ImgProxy(test_key, test_salt)

    img_path = imp.generate(test_url, test_resize, test_width, test_height, test_gravity, test_enlarge, test_extension)
    print(img_path)