from typing import Any, Optional

from . import utils
from .otp import OTP


class HOTP(OTP):
    """
    Handler for HMAC-based OTP counters.
    """
    def __init__(self, *args: Any, initial_count: int = 0, **kwargs: Any) -> None:
        """
        :param initial_count: starting HMAC counter value, defaults to 0
        """
        self.initial_count = initial_count
        super(HOTP, self).__init__(*args, **kwargs)

    def at(self, count: int) -> str:
        """
        Generates the OTP for the given count.

        :param count: the OTP HMAC counter
        :returns: OTP
        """
        return self.generate_otp(count)

    def verify(self, otp: str, counter: int) -> bool:
        """
        Verifies the OTP passed in against the current counter OTP.

        :param otp: the OTP to check against
        :param counter: the OTP HMAC counter
        """
        return utils.strings_equal(str(otp), str(self.at(counter)))

    def provisioning_uri(
            self,
            name: Optional[str] = None,
            initial_count: Optional[int] = None,
            issuer_name: Optional[str] = None) -> str:
        """
        Returns the provisioning URI for the OTP.  This can then be
        encoded in a QR Code and used to provision an OTP app like
        Google Authenticator.

        See also:
            https://github.com/google/google-authenticator/wiki/Key-Uri-Format

        :param name: name of the user account
        :param initial_count: starting HMAC counter value, defaults to 0
        :param issuer_name: the name of the OTP issuer; this will be the
            organization title of the OTP entry in Authenticator
        :returns: provisioning URI
        """
        return utils.build_uri(
            self.secret,
            name=name if name else self.name,
            initial_count=initial_count if initial_count else self.initial_count,
            issuer=issuer_name if issuer_name else self.issuer,
            algorithm=self.digest().name,
            digits=self.digits
        )