"""
flask_httpauth
==================

This module provides Basic and Digest HTTP authentication for Flask routes.

:copyright: (C) 2014 by Miguel Grinberg.
:license:   BSD, see LICENSE for more details.
"""

from functools import wraps
from hashlib import md5
from random import Random, SystemRandom
from flask import request, make_response, session
from werkzeug.datastructures import Authorization


class HTTPAuth(object):
    def __init__(self, scheme=None, realm=None):
        self.scheme = scheme
        self.realm = realm or "Authentication Required"
        self.get_password_callback = None
        self.auth_error_callback = None

        def default_get_password(username):
            return None

        def default_auth_error():
            return "Unauthorized Access"

        self.get_password(default_get_password)
        self.error_handler(default_auth_error)

    def get_password(self, f):
        self.get_password_callback = f
        return f

    def error_handler(self, f):
        @wraps(f)
        def decorated(*args, **kwargs):
            res = f(*args, **kwargs)
            res = make_response(res)
            if res.status_code == 200:
                # if user didn't set status code, use 401
                res.status_code = 401
            if 'WWW-Authenticate' not in res.headers.keys():
                res.headers['WWW-Authenticate'] = self.authenticate_header()
            return res
        self.auth_error_callback = decorated
        return decorated

    def authenticate_header(self):
        return '{0} realm="{1}"'.format(self.scheme, self.realm)

    def login_required(self, f):
        @wraps(f)
        def decorated(*args, **kwargs):
            auth = request.authorization
            if auth is None and 'Authorization' in request.headers:
                # Flask/Werkzeug do not recognize any authentication types
                # other than Basic or Digest, so here we parse the header by
                # hand
                try:
                    auth_type, token = request.headers['Authorization'].split(
                        None, 1)
                    auth = Authorization(auth_type, {'token': token})
                except ValueError:
                    # The Authorization header is either empty or has no token
                    pass

            # if the auth type does not match, we act as if there is no auth
            # this is better than failing directly, as it allows the callback
            # to handle special cases, like supporting multiple auth types
            if auth is not None and auth.type.lower() != self.scheme.lower():
                auth = None

            # Flask normally handles OPTIONS requests on its own, but in the
            # case it is configured to forward those to the application, we
            # need to ignore authentication headers and let the request through
            # to avoid unwanted interactions with CORS.
            if request.method != 'OPTIONS':  # pragma: no cover
                if auth and auth.username:
                    password = self.get_password_callback(auth.username)
                else:
                    password = None
                if not self.authenticate(auth, password):
                    return self.auth_error_callback()
            return f(*args, **kwargs)
        return decorated

    def username(self):
        if not request.authorization:
            return ""
        return request.authorization.username


class HTTPBasicAuth(HTTPAuth):
    def __init__(self, scheme=None, realm=None):
        super(HTTPBasicAuth, self).__init__(scheme or 'Basic', realm)

        self.hash_password_callback = None
        self.verify_password_callback = None

    def hash_password(self, f):
        self.hash_password_callback = f
        return f

    def verify_password(self, f):
        self.verify_password_callback = f
        return f

    def authenticate(self, auth, stored_password):
        if auth:
            username = auth.username
            client_password = auth.password
        else:
            username = ""
            client_password = ""
        if self.verify_password_callback:
            return self.verify_password_callback(username, client_password)
        if not auth:
            return False
        if self.hash_password_callback:
            try:
                client_password = self.hash_password_callback(client_password)
            except TypeError:
                client_password = self.hash_password_callback(username,
                                                              client_password)
        return client_password is not None and \
            client_password == stored_password


class HTTPDigestAuth(HTTPAuth):
    def __init__(self, scheme=None, realm=None, use_ha1_pw=False):
        super(HTTPDigestAuth, self).__init__(scheme or 'Digest', realm)
        self.use_ha1_pw = use_ha1_pw
        self.random = SystemRandom()
        try:
            self.random.random()
        except NotImplementedError:  # pragma: no cover
            self.random = Random()

        self.generate_nonce_callback = None
        self.verify_nonce_callback = None
        self.generate_opaque_callback = None
        self.verify_opaque_callback = None

        def _generate_random():
            return md5(str(self.random.random()).encode('utf-8')).hexdigest()

        def default_generate_nonce():
            session["auth_nonce"] = _generate_random()
            return session["auth_nonce"]

        def default_verify_nonce(nonce):
            return nonce == session.get("auth_nonce")

        def default_generate_opaque():
            session["auth_opaque"] = _generate_random()
            return session["auth_opaque"]

        def default_verify_opaque(opaque):
            return opaque == session.get("auth_opaque")

        self.generate_nonce(default_generate_nonce)
        self.generate_opaque(default_generate_opaque)
        self.verify_nonce(default_verify_nonce)
        self.verify_opaque(default_verify_opaque)

    def generate_nonce(self, f):
        self.generate_nonce_callback = f
        return f

    def verify_nonce(self, f):
        self.verify_nonce_callback = f
        return f

    def generate_opaque(self, f):
        self.generate_opaque_callback = f
        return f

    def verify_opaque(self, f):
        self.verify_opaque_callback = f
        return f

    def get_nonce(self):
        return self.generate_nonce_callback()

    def get_opaque(self):
        return self.generate_opaque_callback()

    def generate_ha1(self, username, password):
        a1 = username + ":" + self.realm + ":" + password
        a1 = a1.encode('utf-8')
        return md5(a1).hexdigest()

    def authenticate_header(self):
        nonce = self.get_nonce()
        opaque = self.get_opaque()
        return '{0} realm="{1}",nonce="{2}",opaque="{3}"'.format(
            self.scheme, self.realm, nonce,
            opaque)

    def authenticate(self, auth, stored_password_or_ha1):
        if not auth or not auth.username or not auth.realm or not auth.uri \
                or not auth.nonce or not auth.response \
                or not stored_password_or_ha1:
            return False
        if not(self.verify_nonce_callback(auth.nonce)) or \
                not(self.verify_opaque_callback(auth.opaque)):
            return False
        if self.use_ha1_pw:
            ha1 = stored_password_or_ha1
        else:
            a1 = auth.username + ":" + auth.realm + ":" + \
                stored_password_or_ha1
            ha1 = md5(a1.encode('utf-8')).hexdigest()
        a2 = request.method + ":" + auth.uri
        ha2 = md5(a2.encode('utf-8')).hexdigest()
        a3 = ha1 + ":" + auth.nonce + ":" + ha2
        response = md5(a3.encode('utf-8')).hexdigest()
        return response == auth.response


class HTTPTokenAuth(HTTPAuth):
    def __init__(self, scheme='Bearer', realm=None):
        super(HTTPTokenAuth, self).__init__(scheme, realm)

        self.verify_token_callback = None

    def verify_token(self, f):
        self.verify_token_callback = f
        return f

    def authenticate(self, auth, stored_password):
        if auth:
            token = auth['token']
        else:
            token = ""
        if self.verify_token_callback:
            return self.verify_token_callback(token)
        return False


class MultiAuth(object):
    def __init__(self, main_auth, *args):
        self.main_auth = main_auth
        self.additional_auth = args

    def login_required(self, f):
        @wraps(f)
        def decorated(*args, **kwargs):
            selected_auth = None
            if 'Authorization' in request.headers:
                scheme, creds = request.headers['Authorization'].split(None, 1)
                for auth in self.additional_auth:
                    if auth.scheme == scheme:
                        selected_auth = auth
                        break
            if selected_auth is None:
                selected_auth = self.main_auth
            return selected_auth.login_required(f)(*args, **kwargs)
        return decorated