#!/usr/bin/python2.5

#

# Copyright 2008 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Access control helper.

The functions in this module can be used to check access control

related requirements. When the specified required conditions are not

met, an exception is raised. This exception contains a views that

either prompts for authentication, or informs the user that they

do not meet the required criteria.

"""

__authors__ = [

  '"Todd Larsen" <tlarsen@google.com>',

  '"Sverre Rabbelier" <sverre@rabbelier.nl>',

  '"Lennard de Rijk" <ljvderijk@gmail.com>',

  '"Pawel Solyga" <pawel.solyga@gmail.com>',

  ]

from google.appengine.api import users

from google.appengine.api import memcache

from django.core import urlresolvers

from django.utils.translation import ugettext

from soc.logic import accounts

from soc.logic import dicts

from soc.logic.models.club_admin import logic as club_admin_logic

from soc.logic.models.host import logic as host_logic

from soc.logic.models.notification import logic as notification_logic

from soc.logic.models.request import logic as request_logic

from soc.logic.models.role import logic as role_logic

from soc.logic.models.site import logic as site_logic

from soc.logic.models.user import logic as user_logic

from soc.views import helper

from soc.views import out_of_band

from soc.views.helper import redirects

DEF_NO_USER_LOGIN_MSG= ugettext(

  'Please create <a href="/user/create_profile">User Profile</a>'

  ' in order to view this page.')

DEF_AGREE_TO_TOS_MSG_FMT = ugettext(

  'You must agree to the <a href="%(tos_link)s">site-wide Terms of'

  ' Service</a> in your <a href="/user/edit_profile">User Profile</a>'

  ' in order to view this page.')

DEF_DEV_LOGOUT_LOGIN_MSG_FMT = ugettext(

  'Please <a href="%%(sign_out)s">sign out</a>'

  ' and <a href="%%(sign_in)s">sign in</a>'

  ' again as %(role)s to view this page.')

DEF_PAGE_DENIED_MSG = ugettext(

  'Access to this page has been restricted')

DEF_LOGOUT_MSG_FMT = ugettext(

    'Please <a href="%(sign_out)s">sign out</a> in order to view this page')

DEF_GROUP_NOT_FOUND_MSG = ugettext(

    'The requested Group can not be found')

DEF_USER_ACCOUNT_INVALID_MSG_FMT = ugettext(

    'The <b><i>%(email)s</i></b> account cannot be used with this site, for'

    ' one or more of the following reasons:'

    '<ul>'

    ' <li>the account is invalid</li>'

    ' <li>the account is already attached to a User profile and cannot be'

    ' used to create another one</li>'

    ' <li>the account is a former account that cannot be used again</li>'

    '</ul>')

def denySidebar(fun):

  """Decorator that denies access if the sidebar is calling.

  """

  from functools import wraps

  @wraps(fun)

  def wrapper(self, django_args, *args, **kwargs):

    if django_args.get('SIDEBAR_CALLING'):

      raise out_of_band.Error("Sidebar Calling")

    return fun(self, django_args, *args, **kwargs)

  return wrapper

def allowDeveloper(fun):

  """Decorator that allows access if the current user is a Developer.

  """

  from functools import wraps

  @wraps(fun)

  def wrapper(self, django_args, *args, **kwargs):

    try:

      # if the current user is a developer we allow access

      return self.checkIsDeveloper(django_args)

    except out_of_band.Error:

      return fun(self, django_args, *args, **kwargs)

  return wrapper

class Checker(object):

  """

  The __setitem__() and __getitem__() methods are overloaded to DTRT

  when adding new access rights, and retrieving them, so use these

  rather then modifying rights directly if so desired.

  """

  def __init__(self, params):

    """Adopts base.rights as rights if base is set.

    """

    base = params.get('rights') if params else None

    self.rights = base.rights if base else {}

    self.id = None

    self.user = None

  def __setitem__(self, key, value):

    """Sets a value only if no old value exists.

    """

    oldvalue = self.rights.get(key)

    self.rights[key] = oldvalue if oldvalue else value

  def __getitem__(self, key):

    """Retrieves the right checkers and massages then into a default format.

    The result is guaranteed to be a list of 2-tuples, the first element is a

    checker (iff there is an checker with the specified name), the second

    element is a list of arguments that should be passed to the checker when

    calling it in addition to the standard django_args.

    """

    result = []

    for i in self.rights.get(key, []):

      # Be nice an repack so that it is always a list with tuples

      if isinstance(i, tuple):

        name, arg = i

        tmp = (name, (arg if isinstance(arg, list) else [arg]))

        result.append(tmp)

      else:

        tmp = (i, [])

        result.append(tmp)

    return result

  def key(self, checker_name):

    """Returns the key for the specified checker for the current user.

    """

    return "%s.%s" % (self.id, checker_name)

  def put(self, checker_name, value):

    """Puts the result for the specified checker in the cache.

    """

    retention = 30

    memcache_key = self.key(checker_name)

    memcache.add(memcache_key, value, retention)

  def get(self, checker_name):

    """Retrieves the result for the specified checker from cache.

    """

    memcache_key = self.key(checker_name)

    return memcache.get(memcache_key)

  def doCheck(self, checker_name, django_args, args):

    """Runs the specified checker with the specified arguments.

    """

    checker = getattr(self, checker_name)

    checker(django_args, *args)

  def doCachedCheck(self, checker_name, django_args, args):

    """Retrieves from cache or runs the specified checker.

    """

    cached = self.get(checker_name)

    if cached is None:

      try:

        self.doCheck(checker_name, django_args, args)

        self.put(checker_name, True)

        return

      except out_of_band.Error, e:

        self.put(checker_name, e)

        raise

    if cached is True:

      return

    # re-raise the cached exception

    raise cached

  def check(self, use_cache, checker_name, django_args, args):

    """Runs the checker, optionally using the cache.

    """

    if use_cache:

      self.doCachedCheck(checker_name, django_args, args)

    else:

      self.doCheck(checker_name, django_args, args)

  def setCurrentUser(self, id, user):

    """Sets up everything for the current user.

    """

    self.id = id

    self.user = user

  def checkAccess(self, access_type, django_args):

    """Runs all the defined checks for the specified type.

    Args:

      access_type: the type of request (such as 'list' or 'edit')

      rights: a dictionary containing access check functions

      django_args: a dictionary with django's arguments

    Rights usage:

      The rights dictionary is used to check if the current user is allowed

      to view the page specified. The functions defined in this dictionary

      are always called with the provided django_args dictionary as argument. On any

      request, regardless of what type, the functions in the 'any_access' value

      are called. If the specified type is not in the rights dictionary, all

      the functions in the 'unspecified' value are called. When the specified

      type _is_ in the rights dictionary, all the functions in that access_type's

      value are called.

    """

    use_cache = django_args.get('SIDEBAR_CALLING')

    # Call each access checker

    for checker_name, args in self['any_access']:

      self.check(use_cache, checker_name, django_args, args)

    if access_type not in self.rights:

      # No checks defined, so do the 'generic' checks and bail out

      for checker_name, args in self['unspecified']:

        self.check(use_cache, checker_name, django_args, args)

      return

    for checker_name, args in self[access_type]:

      self.check(use_cache, checker_name, django_args, args)

  def allow(self, django_args):

    """Never raises an alternate HTTP response.  (an access no-op, basically).

    Args:

      django_args: a dictionary with django's arguments

    """

    return

  def deny(self, django_args):

    """Always raises an alternate HTTP response.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      always raises AccessViolationResponse if called

    """

    context = django_args.get('context', {})

    context['title'] = 'Access denied'

    raise out_of_band.AccessViolation(DEF_PAGE_DENIED_MSG, context=context)

  def checkIsLoggedIn(self, django_args):

    """Raises an alternate HTTP response if Google Account is not logged in.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if no Google Account is even logged in

    """

    if self.id:

      return

    raise out_of_band.LoginRequest()

  def checkNotLoggedIn(self, django_args):

    """Raises an alternate HTTP response if Google Account is logged in.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if a Google Account is currently logged in

    """

    if not self.id:

      return

    raise out_of_band.LoginRequest(message_fmt=DEF_LOGOUT_MSG_FMT)

  def checkIsUser(self, django_args):

    """Raises an alternate HTTP response if Google Account has no User entity.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if no User exists for the logged-in Google Account, or

      * if no Google Account is logged in at all

      * if User has not agreed to the site-wide ToS, if one exists

    """

    self.checkIsLoggedIn(django_args)

    if not self.user:

      raise out_of_band.LoginRequest(message_fmt=DEF_NO_USER_LOGIN_MSG)

    if user_logic.agreesToSiteToS(self.user):

      return

    # Would not reach this point of site-wide ToS did not exist, since

    # agreesToSiteToS() call above always returns True if no ToS is in effect.

    login_msg_fmt = DEF_AGREE_TO_TOS_MSG_FMT % {

        'tos_link': redirects.getToSRedirect(site_logic.getSingleton())}

    raise out_of_band.LoginRequest(message_fmt=login_msg_fmt)

  def checkIsUnusedAccount(self, django_args):

    """Raises an alternate HTTP response if Google Account has a User entity.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if a User exists for the logged-in Google Account, or

      * if a User has this Gooogle Account in their formerAccounts list

    """

    self.checkIsLoggedIn(django_args)

    if not self.user and not user_logic.isFormerAccount(self.id):

      # this account has not been used yet

      return

    message_fmt = DEF_USER_ACCOUNT_INVALID_MSG_FMT % {

        'email' : self.id.email()}

    raise out_of_band.LoginRequest(message_fmt=message_fmt)

  def checkHasUserEntity(self, django_args):

    """Raises an alternate HTTP response if Google Account has no User entity.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if no User exists for the logged-in Google Account, or

      * if no Google Account is logged in at all

    """

    self.checkIsLoggedIn(django_args)

    if not self.user:

      raise out_of_band.LoginRequest(message_fmt=DEF_NO_USER_LOGIN_MSG)

    return

  def checkIsDeveloper(self, django_args):

    """Raises an alternate HTTP response if Google Account is not a Developer.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if User is not a Developer, or

      * if no User exists for the logged-in Google Account, or

      * if no Google Account is logged in at all

    """

    self.checkIsUser(django_args)

    if accounts.isDeveloper(account=self.id):

      return

    login_message_fmt = DEF_DEV_LOGOUT_LOGIN_MSG_FMT % {

        'role': 'a Site Developer '}

    raise out_of_band.LoginRequest(message_fmt=login_message_fmt)

  @allowDeveloper

  @denySidebar

  def checkIsGroupActive(self, django_args, group_logic):

    """Raises an alternate HTTP response if Group state is not active.

    Args:

      django_args: a dictionary with django's arguments

    Raises:

      AccessViolationResponse:

      * if no Group is found

      * if the Group state is not active

    """

    fields = {'link_id': django_args['link_id']}

    if django_args.get('scope_path'):

      fields['scope_path'] = django_args['scope_path']

    group_entity = group_logic.logic.getFromFieldsOr404(**fields)

    if group_entity.state == 'active':

      return

    # TODO tell the user that this group is not active

    self.deny(django_args)

  def checkCanMakeRequestToGroup(self, django_args, group_logic):

    """Raises an alternate HTTP response if the specified group is not in an

    active state.

    Note that state hasn't been implemented yet

    Args:

      group_logic: Logic module for the type of group which the request is for

    """

    group_entity = role_logic.getGroupEntityFromScopePath(

        group_logic.logic, django_args['scope_path'])

    if not group_entity:

      raise out_of_band.Error(DEF_GROUP_NOT_FOUND_MSG, status=404)

    if group_entity.state != 'active':

      # TODO tell the user that this group is not active

      self.deny(django_args)

    return

  def checkCanCreateFromRequest(self, django_args, role_name):

    """Raises an alternate HTTP response if the specified request does not exist

       or if it's state is not group_accepted. Also when the group this request

       is from is in an inactive or invalid state access will be denied.

    """

    self.checkIsUser(django_args)

    user_entity = user_logic.getForCurrentAccount()

    if user_entity.link_id != django_args['link_id']:

      self.deny(django_args)

    fields = {'link_id': django_args['link_id'],

        'scope_path': django_args['scope_path'],

        'role': role_name}

    request_entity = request_logic.getFromFieldsOr404(**fields)

    if request_entity.state != 'group_accepted':

      # TODO tell the user that this request has not been accepted yet

      self.deny(django_args)

    if request_entity.scope.state in ['invalid', 'inactive']:

      # TODO tell the user that it is not possible to create this role anymore

      self.deny(django_args)

    return