# copyright 2003-2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr

#

# This file is part of CubicWeb.

#

# CubicWeb is free software: you can redistribute it and/or modify it under the

# terms of the GNU Lesser General Public License as published by the Free

# Software Foundation, either version 2.1 of the License, or (at your option)

# any later version.

#

# CubicWeb 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 Lesser General Public License for more

# details.

#

# You should have received a copy of the GNU Lesser General Public License along

# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

"""Security hooks: check permissions to add/delete/update entities according to

the user connected to a session

"""

__docformat__ = "restructuredtext en"

from logilab.common.registry import objectify_predicate

from yams import buildobjs

from cubicweb import Unauthorized

from cubicweb.server import BEFORE_ADD_RELATIONS, ON_COMMIT_ADD_RELATIONS, hook

_DEFAULT_UPDATE_ATTRPERM = buildobjs.DEFAULT_ATTRPERMS['update']

def check_entity_attributes(session, entity, editedattrs=None, creation=False):

    eid = entity.eid

    eschema = entity.e_schema

    # ._cw_skip_security_attributes is there to bypass security for attributes

    # set by hooks by modifying the entity's dictionary

    if editedattrs is None:

        editedattrs = entity.cw_edited

    dontcheck = editedattrs.skip_security

    for attr in editedattrs:

        if attr in dontcheck:

            continue

        rdef = eschema.rdef(attr)

        if rdef.final: # non final relation are checked by standard hooks

            # attributes only have a specific 'update' permission

            updateperm = rdef.permissions.get('update')

            # comparison below works because the default update perm is:

            #

            #  ('managers', ERQLExpression(Any X WHERE U has_update_permission X, X eid %(x)s, U eid %(u)s))

            #

            # is deserialized in this order (groups first), and ERQLExpression

            # implements comparison by expression.

            if updateperm == _DEFAULT_UPDATE_ATTRPERM:

                # The default update permission is to delegate to the entity

                # update permission. This is an historical artefact but it is

                # costly (in general). Hence we take this permission object as a

                # marker saying "no specific" update permissions for this

                # attribute. Thus we just do nothing.

                continue

            if creation and updateperm == ():

                # That actually means an immutable attribute.  We make an

                # _exception_ to the `check attr update perms at entity create &

                # update time` rule for this case.

                continue

            rdef.check_perm(session, 'update', eid=eid)

class CheckEntityPermissionOp(hook.DataOperationMixIn, hook.LateOperation):

    def precommit_event(self):

        session = self.session

        for eid, action, edited in self.get_data():

            entity = session.entity_from_eid(eid)

            entity.cw_check_perm(action)

            check_entity_attributes(session, entity, edited,

                                    creation=(action == 'add'))

class CheckRelationPermissionOp(hook.DataOperationMixIn, hook.LateOperation):

    def precommit_event(self):

        session = self.session

        for action, rschema, eidfrom, eidto in self.get_data():

            rdef = rschema.rdef(session.describe(eidfrom)[0],

                                session.describe(eidto)[0])

            rdef.check_perm(session, action, fromeid=eidfrom, toeid=eidto)

@objectify_predicate

def write_security_enabled(cls, req, **kwargs):

    if req is None or not req.write_security:

        return 0

    return 1

class SecurityHook(hook.Hook):

    __abstract__ = True

    category = 'security'

    __select__ = hook.Hook.__select__ & write_security_enabled()

class AfterAddEntitySecurityHook(SecurityHook):

    __regid__ = 'securityafteraddentity'

    events = ('after_add_entity',)

    def __call__(self):

        CheckEntityPermissionOp.get_instance(self._cw).add_data(

            (self.entity.eid, 'add', self.entity.cw_edited) )

class AfterUpdateEntitySecurityHook(SecurityHook):

    __regid__ = 'securityafterupdateentity'

    events = ('after_update_entity',)

    def __call__(self):

        try:

            # check user has permission right now, if not retry at commit time

            self.entity.cw_check_perm('update')

            check_entity_attributes(self._cw, self.entity)

        except Unauthorized:

            self.entity._cw_clear_local_perm_cache('update')

            # save back editedattrs in case the entity is reedited later in the

            # same transaction, which will lead to cw_edited being

            # overwritten

            CheckEntityPermissionOp.get_instance(self._cw).add_data(

                (self.entity.eid, 'update', self.entity.cw_edited) )

class BeforeDelEntitySecurityHook(SecurityHook):

    __regid__ = 'securitybeforedelentity'

    events = ('before_delete_entity',)

    def __call__(self):

        self.entity.cw_check_perm('delete')

class BeforeAddRelationSecurityHook(SecurityHook):

    __regid__ = 'securitybeforeaddrelation'

    events = ('before_add_relation',)

    def __call__(self):

        if self.rtype in BEFORE_ADD_RELATIONS:

            nocheck = self._cw.transaction_data.get('skip-security', ())

            if (self.eidfrom, self.rtype, self.eidto) in nocheck:

                return

            rschema = self._cw.repo.schema[self.rtype]

            rdef = rschema.rdef(self._cw.describe(self.eidfrom)[0],

                                self._cw.describe(self.eidto)[0])

            rdef.check_perm(self._cw, 'add', fromeid=self.eidfrom, toeid=self.eidto)

class AfterAddRelationSecurityHook(SecurityHook):

    __regid__ = 'securityafteraddrelation'

    events = ('after_add_relation',)

    def __call__(self):

        if not self.rtype in BEFORE_ADD_RELATIONS:

            nocheck = self._cw.transaction_data.get('skip-security', ())

            if (self.eidfrom, self.rtype, self.eidto) in nocheck:

                return

            rschema = self._cw.repo.schema[self.rtype]

            if self.rtype in ON_COMMIT_ADD_RELATIONS:

                CheckRelationPermissionOp.get_instance(self._cw).add_data(

                    ('add', rschema, self.eidfrom, self.eidto) )

            else:

                rdef = rschema.rdef(self._cw.describe(self.eidfrom)[0],

                                    self._cw.describe(self.eidto)[0])

                rdef.check_perm(self._cw, 'add', fromeid=self.eidfrom, toeid=self.eidto)

class BeforeDeleteRelationSecurityHook(SecurityHook):

    __regid__ = 'securitybeforedelrelation'

    events = ('before_delete_relation',)

    def __call__(self):

        nocheck = self._cw.transaction_data.get('skip-security', ())

        if (self.eidfrom, self.rtype, self.eidto) in nocheck:

            return

        rschema = self._cw.repo.schema[self.rtype]

        rdef = rschema.rdef(self._cw.describe(self.eidfrom)[0],

                            self._cw.describe(self.eidto)[0])

        rdef.check_perm(self._cw, 'delete', fromeid=self.eidfrom, toeid=self.eidto)