# -*- coding: utf-8 -*-
"""
vk.com OpenAPI and OAuth 2.0 support.

This contribution adds support for VK.com OpenAPI, OAuth 2.0 and IFrame apps.
Username is retrieved from the identity returned by server.
"""

from django.contrib.auth import authenticate
from django.utils import simplejson

from urllib import urlencode
from hashlib import md5
from time import time

from social_auth.backends import SocialAuthBackend, OAuthBackend, BaseAuth, \
                                 BaseOAuth2
from social_auth.exceptions import AuthTokenRevoked, AuthException, \
                                   AuthCanceled, AuthFailed
from social_auth.utils import setting, log, dsa_urlopen


# vk configuration
VK_AUTHORIZATION_URL = 'http://oauth.vk.com/authorize'
VK_ACCESS_TOKEN_URL = 'https://oauth.vk.com/access_token'
VK_SERVER = 'vk.com'
VK_DEFAULT_DATA = ['first_name', 'last_name', 'screen_name',
                   'nickname', 'photo']

VK_API_URL = 'https://api.vk.com/method/'
VK_SERVER_API_URL = 'http://api.vk.com/api.php'
VK_API_VERSION = '3.0'

LOCAL_HTML = setting('VK_LOCAL_HTML', setting('VKONTAKTE_LOCAL_HTML',
                                              'vkontakte.html'))

USE_APP_AUTH = setting('VKAPP_APP_ID', False)


class VKOpenAPIBackend(SocialAuthBackend):
    """VK OpenAPI authentication backend"""
    name = 'vk-openapi'

    def get_user_id(self, details, response):
        """Return user unique id provided by VK"""
        return response['id']

    def get_user_details(self, response):
        """Return user details from VK request"""
        nickname = response.get('nickname') or response['id']
        if isinstance(nickname, (list, tuple, )):
            nickname = nickname[0]
        return {
            'username': nickname,
            'email': '',
            'fullname': '',
            'first_name': response.get('first_name')[0]
                                if 'first_name' in response else '',
            'last_name': response.get('last_name')[0]
                                if 'last_name' in response else ''
        }


class VKOpenAPIAuth(BaseAuth):
    """VKontakte OpenAPI authorization mechanism"""
    AUTH_BACKEND = VKOpenAPIBackend
    APP_ID = setting('VKONTAKTE_APP_ID')

    def user_data(self, access_token, *args, **kwargs):
        return dict(self.request.GET)

    def auth_html(self):
        """Returns local VK authentication page, not necessary for
        VK to authenticate.
        """
        from django.template import RequestContext, loader

        dict = {'VK_APP_ID': self.APP_ID,
                'VK_COMPLETE_URL': self.redirect}

        vk_template = loader.get_template(LOCAL_HTML)
        context = RequestContext(self.request, dict)

        return vk_template.render(context)

    def auth_complete(self, *args, **kwargs):
        """Performs check of authentication in VK, returns User if
        succeeded"""
        app_cookie = 'vk_app_' + self.APP_ID

        if not 'id' in self.request.GET or \
           not app_cookie in self.request.COOKIES:
            raise AuthCanceled(self)

        cookie_dict = dict(item.split('=') for item in
                                self.request.COOKIES[app_cookie].split('&'))
        check_str = ''.join(item + '=' + cookie_dict[item]
                                for item in ['expire', 'mid', 'secret', 'sid'])

        hash = md5(check_str + setting('VK_API_SECRET')).hexdigest()

        if hash != cookie_dict['sig'] or int(cookie_dict['expire']) < time():
            raise AuthFailed('VK authentication failed: invalid hash')
        else:
            kwargs.update({
                'auth': self,
                'response': self.user_data(cookie_dict['mid']),
                self.AUTH_BACKEND.name: True
            })
            return authenticate(*args, **kwargs)

    @property
    def uses_redirect(self):
        """VK does not require visiting server url in order
        to do authentication, so auth_xxx methods are not needed to be called.
        Their current implementation is just an example"""
        return False


class VKOAuth2Backend(OAuthBackend):
    """VKOAuth2 authentication backend"""
    name = 'vk-oauth'

    EXTRA_DATA = [
        ('id', 'id'),
        ('expires', 'expires')
    ]

    def get_user_id(self, details, response):
        """OAuth providers return an unique user id in response"""
        return response['user_id']

    def get_user_details(self, response):
        """Return user details from VK account"""
        return {
            'username': response.get('screen_name'),
            'email': '',
            'first_name': response.get('first_name'),
            'last_name': response.get('last_name')
        }


class VKApplicationBackend(VKOAuth2Backend):
    name = 'vk-app'


class VKOAuth2(BaseOAuth2):
    """VK OAuth mechanism"""
    AUTHORIZATION_URL = VK_AUTHORIZATION_URL
    ACCESS_TOKEN_URL = VK_ACCESS_TOKEN_URL
    AUTH_BACKEND = VKOAuth2Backend
    SETTINGS_KEY_NAME = 'VK_APP_ID'
    SETTINGS_SECRET_NAME = 'VK_API_SECRET'
    # Look at:
    # http://vk.com/developers.php?oid=-17680044&p=Application_Access_Rights
    SCOPE_VAR_NAME = 'VK_EXTRA_SCOPE'

    def get_scope(self):
        return setting(VKOAuth2.SCOPE_VAR_NAME) or \
               setting('VK_OAUTH2_EXTRA_SCOPE')

    def user_data(self, access_token, response, *args, **kwargs):
        """Loads user data from service"""
        fields = ','.join(VK_DEFAULT_DATA + setting('VK_EXTRA_DATA', []))
        params = {'access_token': access_token,
                  'fields': fields,
                  'uids': response.get('user_id')}

        data = vk_api('users.get', params)

        if data.get('error'):
            error = data['error']
            msg = error.get('error_msg', 'Unknown error')
            if error.get('error_code') == 5:
                raise AuthTokenRevoked(self, msg)
            else:
                raise AuthException(self, msg)

        if data:
            data = data.get('response')[0]
            data['user_photo'] = data.get('photo')  # Backward compatibility

        return data


class VKAppAuth(VKOAuth2):
    """VKontakte Application Authentication support"""
    AUTH_BACKEND = VKApplicationBackend
    SETTINGS_KEY_NAME = 'VKAPP_APP_ID'
    SETTINGS_SECRET_NAME = 'VKAPP_API_SECRET'

    def auth_complete(self, *args, **kwargs):
        stop, app_auth = self.application_auth(*args, **kwargs)

        if app_auth:
            return app_auth

        if stop:
            return None

        return super(VKAppAuth, self).auth_complete(*args, **kwargs)

    def user_profile(self, user_id, access_token=None):
        data = {'uids': user_id, 'fields': 'photo'}

        if access_token:
            data['access_token'] = access_token

        profiles = vk_api('getProfiles', data, is_app=True).get('response',
                                                                None)
        return profiles[0] if profiles else None

    def is_app_user(self, user_id, access_token=None):
        """Returns app usage flag from VK API"""

        data = {'uid': user_id}

        if access_token:
            data['access_token'] = access_token

        return vk_api('isAppUser', data, is_app=True).get('response', 0)

    def application_auth(self, *args, **kwargs):
        required_params = ('is_app_user', 'viewer_id', 'access_token',
                           'api_id')

        for param in required_params:
            if not param in self.request.REQUEST:
                return (False, None)

        auth_key = self.request.REQUEST.get('auth_key')

        # Verify signature, if present
        if auth_key:
            check_key = md5('_'.join([
                setting(self.SETTINGS_KEY_NAME),
                self.request.REQUEST.get('viewer_id'),
                setting(self.SETTINGS_SECRET_NAME)
            ])).hexdigest()

            if check_key != auth_key:
                raise ValueError('VK authentication failed: invalid '
                                 'auth key')

        user_check = setting('VKAPP_USER_MODE', 0)
        user_id = self.request.REQUEST.get('viewer_id')

        if user_check:
            is_user = self.request.REQUEST.get('is_app_user') \
                        if user_check == 1 else self.is_app_user(user_id)

            if not int(is_user):
                return (True, None)

        data = self.user_profile(user_id)
        data['user_id'] = user_id

        return (True, authenticate(*args, **{'auth': self,
            'request': self.request,
            'response': data, self.AUTH_BACKEND.name: True
        }))


def vk_api(method, data, is_app=False):
    """Calls VK OpenAPI method
        https://vk.com/apiclub,
        https://vk.com/pages.php?o=-1&p=%C2%FB%EF%EE%EB%ED%E5%ED%E8%E5%20%E7'
                                        %E0%EF%F0%EE%F1%EE%E2%20%EA%20API
    """

    # We need to perform server-side call if no access_token
    if not 'access_token' in data:
        if not 'v' in data:
            data['v'] = VK_API_VERSION

        if not 'api_id' in data:
            data['api_id'] = setting('VKAPP_APP_ID' if is_app else 'VK_APP_ID')

        data['method'] = method
        data['format'] = 'json'

        url = VK_SERVER_API_URL
        secret = setting('VKAPP_API_SECRET' if is_app else 'VK_API_SECRET')

        param_list = sorted(list(item + '=' + data[item] for item in data))
        data['sig'] = md5(''.join(param_list) + secret).hexdigest()
    else:
        url = VK_API_URL + method

    params = urlencode(data)
    url += '?' + params
    try:
        return simplejson.load(dsa_urlopen(url))
    except (TypeError, KeyError, IOError, ValueError, IndexError):
        log('error', 'Could not load data from vk.com',
            exc_info=True, extra=dict(data=data))
        return None


# Backend definition
BACKENDS = {
    'vk-openapi': VKOpenAPIAuth,
    'vk-oauth': VKOAuth2 if not USE_APP_AUTH else VKAppAuth,
}
