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

the user connected to a session

"""

__docformat__ = "restructuredtext en"

from cubicweb import Unauthorized

from cubicweb.selectors import objectify_selector, lltrace

from cubicweb.server import BEFORE_ADD_RELATIONS, ON_COMMIT_ADD_RELATIONS, hook

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

    eid = entity.eid

    eschema = entity.e_schema

    # .skip_security_attributes is there to bypass security for attributes

    # set by hooks by modifying the entity's dictionnary

    dontcheck = entity.skip_security_attributes

    if editedattrs is None:

        try:

            editedattrs = entity.edited_attributes

        except AttributeError:

            editedattrs = entity # XXX unexpected

    for attr in editedattrs:

        if attr in dontcheck:

            continue

        rdef = eschema.rdef(attr)

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

            # add/delete should be equivalent (XXX: unify them into 'update' ?)

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

    # don't update dontcheck until everything went fine: see usage in

    # after_update_entity, where if we got an Unauthorized at hook time, we will

    # retry and commit time

    dontcheck |= frozenset(editedattrs)

class _CheckEntityPermissionOp(hook.LateOperation):

    def precommit_event(self):

        #print 'CheckEntityPermissionOp', self.session.user, self.entity, self.action

        self.entity.check_perm(self.action)

        check_entity_attributes(self.session, self.entity, self.editedattrs)

    def commit_event(self):

        pass

class _CheckRelationPermissionOp(hook.LateOperation):

    def precommit_event(self):

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

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

        rdef.check_perm(self.session, self.action,

                        fromeid=self.eidfrom, toeid=self.eidto)

    def commit_event(self):

        pass

@objectify_selector

@lltrace

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(self._cw, entity=self.entity,

                                 editedattrs=tuple(self.entity.edited_attributes),

                                 action='add')

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.check_perm('update')

            check_entity_attributes(self._cw, self.entity)

        except Unauthorized:

            self.entity.clear_local_perm_cache('update')

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

            # same transaction, which will lead to edited_attributes being

            # overwritten

            _CheckEntityPermissionOp(self._cw, entity=self.entity,

                                     editedattrs=tuple(self.entity.edited_attributes),

                                     action='update')

class BeforeDelEntitySecurityHook(SecurityHook):

    __regid__ = 'securitybeforedelentity'

    events = ('before_delete_entity',)

    def __call__(self):

        self.entity.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(self._cw, action='add',

                                           rschema=rschema,

                                           eidfrom=self.eidfrom,

                                           eidto=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)