# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Credential managers for L{twisted.mail}.
"""

from __future__ import absolute_import, division

import hmac
import hashlib

from zope.interface import implementer

from twisted.cred import credentials
from twisted.python.compat import nativeString
from twisted.mail._except import IllegalClientResponse
from twisted.mail.interfaces import IClientAuthentication, IChallengeResponse


@implementer(IClientAuthentication)
class CramMD5ClientAuthenticator:
    def __init__(self, user):
        self.user = user


    def getName(self):
        return b"CRAM-MD5"


    def challengeResponse(self, secret, chal):
        response = hmac.HMAC(secret, chal, digestmod=hashlib.md5).hexdigest()
        return self.user + b' ' + response.encode('ascii')



@implementer(IClientAuthentication)
class LOGINAuthenticator:
    def __init__(self, user):
        self.user = user
        self.challengeResponse = self.challengeUsername


    def getName(self):
        return b"LOGIN"


    def challengeUsername(self, secret, chal):
        # Respond to something like "Username:"
        self.challengeResponse = self.challengeSecret
        return self.user


    def challengeSecret(self, secret, chal):
        # Respond to something like "Password:"
        return secret



@implementer(IClientAuthentication)
class PLAINAuthenticator:
    def __init__(self, user):
        self.user = user


    def getName(self):
        return b"PLAIN"


    def challengeResponse(self, secret, chal):
        return b'\0' + self.user + b'\0' + secret



@implementer(IChallengeResponse)
class LOGINCredentials(credentials.UsernamePassword):
    def __init__(self):
        self.challenges = [b'Password\0', b'User Name\0']
        self.responses = [b'password', b'username']
        credentials.UsernamePassword.__init__(self, None, None)


    def getChallenge(self):
        return self.challenges.pop()


    def setResponse(self, response):
        setattr(self, nativeString(self.responses.pop()), response)


    def moreChallenges(self):
        return bool(self.challenges)



@implementer(IChallengeResponse)
class PLAINCredentials(credentials.UsernamePassword):
    def __init__(self):
        credentials.UsernamePassword.__init__(self, None, None)


    def getChallenge(self):
        return b''


    def setResponse(self, response):
        parts = response.split(b'\0')
        if len(parts) != 3:
            raise IllegalClientResponse(
                "Malformed Response - wrong number of parts")
        useless, self.username, self.password = parts


    def moreChallenges(self):
        return False


__all__ = [
    "CramMD5ClientAuthenticator",
    "LOGINCredentials", "LOGINAuthenticator",
    "PLAINCredentials", "PLAINAuthenticator",
]
