# -*- coding: utf-8 -*-
# session.py
# Copyright (C) 2017 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Twisted resource containing an authenticated Soledad session.
"""
from zope.interface import implementer

from twisted.cred.credentials import Anonymous
from twisted.cred import error
from twisted.python import log
from twisted.python.components import registerAdapter
from twisted.web import util
from twisted.web._auth import wrapper
from twisted.web.guard import HTTPAuthSessionWrapper
from twisted.web.resource import ErrorPage
from twisted.web.resource import IResource
from twisted.web.server import Session

from zope.interface import Interface
from zope.interface import Attribute

from leap.soledad.server.auth import credentialFactory
from leap.soledad.server.url_mapper import URLMapper


class ISessionData(Interface):
    username = Attribute('An uuid.')
    password = Attribute('A token.')


@implementer(ISessionData)
class SessionData(object):
    def __init__(self, session):
        self.username = None
        self.password = None


registerAdapter(SessionData, Session, ISessionData)


def _sessionData(request):
    session = request.getSession()
    data = ISessionData(session)
    return data


@implementer(IResource)
class UnauthorizedResource(wrapper.UnauthorizedResource):
    isLeaf = True

    def __init__(self):
        pass

    def render(self, request):
        request.setResponseCode(401)
        if request.method == b'HEAD':
            return b''
        return b'Unauthorized'

    def getChildWithDefault(self, path, request):
        return self


@implementer(IResource)
class SoledadSession(HTTPAuthSessionWrapper):

    def __init__(self, portal):
        self._mapper = URLMapper()
        self._portal = portal
        self._credentialFactory = credentialFactory
        # expected by the contract of the parent class
        self._credentialFactories = [credentialFactory]

    def _matchPath(self, request):
        match = self._mapper.match(request.path, request.method)
        return match

    def _parseHeader(self, header):
        elements = header.split(b' ')
        scheme = elements[0].lower()
        if scheme == self._credentialFactory.scheme:
            return (b' '.join(elements[1:]))
        return None

    def _authorizedResource(self, request):
        # check whether the path of the request exists in the app
        match = self._matchPath(request)
        if not match:
            return UnauthorizedResource()

        # get authorization header or fail
        header = request.getHeader(b'authorization')
        if not header:
            return util.DeferredResource(self._login(Anonymous()))

        # parse the authorization header
        auth_data = self._parseHeader(header)
        if not auth_data:
            return UnauthorizedResource()

        # decode the credentials from the parsed header
        try:
            credentials = self._credentialFactory.decode(auth_data, request)
        except error.LoginFailed:
            return UnauthorizedResource()
        except:
            # If you port this to the newer log facility, be aware that
            # the tests rely on the error to be logged.
            log.err(None, "Unexpected failure from credentials factory")
            return ErrorPage(500, None, None)

        # make sure the uuid given in path corresponds to the one given in
        # the credentials
        request_uuid = match.get('uuid')
        if request_uuid and request_uuid != credentials.username:
            return ErrorPage(500, None, None)

        # eventually return a cached resouce
        sessionData = _sessionData(request)
        if sessionData.username == credentials.username \
                and sessionData.password == credentials.password:
            return self._portal.realm.auth_resource

        # if all checks pass, try to login with credentials and cache
        # credentials in case of success
        def _cacheSessionData(res):
            sessionData.username = credentials.username
            sessionData.password = credentials.password
            return res

        d = self._login(credentials)
        d.addCallback(_cacheSessionData)
        return util.DeferredResource(d)