"""Hooks management

This module defined the `Hook` class and registry and a set of abstract classes

for operations.

Hooks are called before / after any individual update of entities / relations

in the repository and on special events such as server startup or shutdown.

Operations may be registered by hooks during a transaction, which will  be

fired when the pool is commited or rollbacked.

Entity hooks (eg before_add_entity, after_add_entity, before_update_entity,

after_update_entity, before_delete_entity, after_delete_entity) all have an

`entity` attribute

Relation (eg before_add_relation, after_add_relation, before_delete_relation,

after_delete_relation) all have `eidfrom`, `rtype`, `eidto` attributes.

Server start/stop hooks (eg server_startup, server_shutdown) have a `repo`

attribute, but *their `cw_req` attribute is None*.

Backup/restore hooks (eg server_backup, server_restore) have a `repo` and a

`timestamp` attributes, but *their `cw_req` attribute is None*.

Session hooks (eg session_open, session_close) have no special attribute.

:organization: Logilab

:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

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

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from warnings import warn

from logging import getLogger

from logilab.common.decorators import classproperty

from logilab.common.logging_ext import set_log_methods

from cubicweb.cwvreg import CWRegistry, VRegistry

from cubicweb.selectors import (objectify_selector, lltrace, match_search_state,

                                entity_implements)

from cubicweb.appobject import AppObject

ENTITIES_HOOKS = set(('before_add_entity',    'after_add_entity',

                      'before_update_entity', 'after_update_entity',

                      'before_delete_entity', 'after_delete_entity'))

RELATIONS_HOOKS = set(('before_add_relation',   'after_add_relation' ,

                       'before_delete_relation','after_delete_relation'))

SYSTEM_HOOKS = set(('server_backup', 'server_restore',

                    'server_startup', 'server_shutdown',

                    'session_open', 'session_close'))

ALL_HOOKS = ENTITIES_HOOKS | RELATIONS_HOOKS | SYSTEM_HOOKS

class HooksRegistry(CWRegistry):

    def register(self, obj, **kwargs):

        for event in obj.events:

            if event not in ALL_HOOKS:

                raise Exception('bad event %s on %s' % (event, obj))

        super(HooksRegistry, self).register(obj, **kwargs)

    def call_hooks(self, event, req=None, **kwargs):

        kwargs['event'] = event

        # XXX remove .enabled

        for hook in sorted([x for x in self.possible_objects(req, **kwargs)

                            if x.enabled], key=lambda x: x.order):

            hook()

VRegistry.REGISTRY_FACTORY['hooks'] = HooksRegistry

# some hook specific selectors #################################################

@objectify_selector

@lltrace

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

    if kwargs.get('event') in cls.events:

        return 1

    return 0

@objectify_selector

@lltrace

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

    if req is None:

        # server startup / shutdown event

        config = kwargs['repo'].config

    else:

        config = req.vreg.config

    if enabled_category in config.disabled_hooks_categories:

        return 0

    return 1

@objectify_selector

@lltrace

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

    if req is None or req.is_super_session:

        return 0

    return 1

class match_rtype(match_search_state):

    """accept if parameters specified as initializer arguments are specified

    in named arguments given to the selector

    :param *expected: parameters (eg `basestring`) which are expected to be

                      found in named arguments (kwargs)

    """

    @lltrace

    def __call__(self, cls, req, *args, **kwargs):

        return kwargs.get('rtype') in self.expected

# base class for hook ##########################################################

class Hook(AppObject):

    __registry__ = 'hooks'

    __select__ = match_event() & enabled_category()

    # set this in derivated classes

    events = None

    category = None

    order = 0

    # XXX deprecates

    enabled = True

    @classproperty

    def __id__(cls):

        warn('[3.5] %s: please specify an id for your hook' % cls)

        return str(id(cls))

    @classmethod

    def __registered__(cls, vreg):

        super(Hook, cls).__registered__(vreg)

        if getattr(cls, 'accepts', None):

            warn('[3.5] %s: accepts is deprecated, define proper __select__' % cls)

            rtypes = []

            for ertype in cls.accepts:

                if ertype.islower():

                    rtypes.append(ertype)

                else:

                    cls.__select__ = cls.__select__ & entity_implements(ertype)

            if rtypes:

                cls.__select__ = cls.__select__ & match_rtype(*rtypes)

        return cls

    known_args = set(('entity', 'rtype', 'eidfrom', 'eidto', 'repo', 'timestamp'))

    def __init__(self, req, event, **kwargs):

        for arg in self.known_args:

            if arg in kwargs:

                setattr(self, arg, kwargs.pop(arg))

        super(Hook, self).__init__(req, **kwargs)

        self.event = event

    def __call__(self):

        if hasattr(self, 'call'):

            warn('[3.5] %s: call is deprecated, implements __call__' % self.__class__)

            if self.event.endswith('_relation'):

                self.call(self.cw_req, self.eidfrom, self.rtype, self.eidto)

            elif 'delete' in self.event:

                self.call(self.cw_req, self.entity.eid)

            elif self.event.startswith('server_'):

                self.call(self.repo)

            elif self.event.startswith('session_'):

                self.call(self.cw_req)

            else:

                self.call(self.cw_req, self.entity)

set_log_methods(Hook, getLogger('cubicweb.hook'))

# abstract classes for operation ###############################################

class Operation(object):

    """an operation is triggered on connections pool events related to

    commit / rollback transations. Possible events are:

    precommit:

      the pool is preparing to commit. You shouldn't do anything things which

      has to be reverted if the commit fail at this point, but you can freely

      do any heavy computation or raise an exception if the commit can't go.

      You can add some new operation during this phase but their precommit

      event won't be triggered

    commit:

      the pool is preparing to commit. You should avoid to do to expensive

      stuff or something that may cause an exception in this event

    revertcommit:

      if an operation failed while commited, this event is triggered for

      all operations which had their commit event already to let them

      revert things (including the operation which made fail the commit)

    rollback:

      the transaction has been either rollbacked either

      * intentionaly

      * a precommit event failed, all operations are rollbacked

      * a commit event failed, all operations which are not been triggered for

        commit are rollbacked

    order of operations may be important, and is controlled according to:

    * operation's class

    """

    def __init__(self, session, **kwargs):

        self.session = session

        self.user = session.user

        self.repo = session.repo

        self.schema = session.repo.schema

        self.config = session.repo.config

        self.__dict__.update(kwargs)

        self.register(session)

        # execution information

        self.processed = None # 'precommit', 'commit'

        self.failed = False

    def register(self, session):

        session.add_operation(self, self.insert_index())

    def insert_index(self):

        """return the index of  the lastest instance which is not a

        LateOperation instance

        """

        for i, op in enumerate(self.session.pending_operations):

            if isinstance(op, (LateOperation, SingleLastOperation)):

                return i

        return None

    def handle_event(self, event):

        """delegate event handling to the opertaion"""

        getattr(self, event)()

    def precommit_event(self):

        """the observed connections pool is preparing a commit"""

    def revertprecommit_event(self):

        """an error went when pre-commiting this operation or a later one

        should revert pre-commit's changes but take care, they may have not

        been all considered if it's this operation which failed

        """

    def commit_event(self):

        """the observed connections pool is commiting"""

    def revertcommit_event(self):

        """an error went when commiting this operation or a later one

        should revert commit's changes but take care, they may have not

        been all considered if it's this operation which failed

        """

    def rollback_event(self):

        """the observed connections pool has been rollbacked

        do nothing by default, the operation will just be removed from the pool

        operation list

        """

set_log_methods(Operation, getLogger('cubicweb.session'))

class LateOperation(Operation):

    """special operation which should be called after all possible (ie non late)

    operations

    """

    def insert_index(self):

        """return the index of  the lastest instance which is not a

        SingleLastOperation instance

        """

        for i, op in enumerate(self.session.pending_operations):

            if isinstance(op, SingleLastOperation):

                return i

        return None

class SingleOperation(Operation):

    """special operation which should be called once"""

    def register(self, session):

        """override register to handle cases where this operation has already

        been added

        """

        operations = session.pending_operations

        index = self.equivalent_index(operations)

        if index is not None:

            equivalent = operations.pop(index)

        else:

            equivalent = None

        session.add_operation(self, self.insert_index())

        return equivalent

    def equivalent_index(self, operations):

        """return the index of the equivalent operation if any"""

        equivalents = [i for i, op in enumerate(operations)

                       if op.__class__ is self.__class__]

        if equivalents:

            return equivalents[0]

        return None

class SingleLastOperation(SingleOperation):

    """special operation which should be called once and after all other

    operations

    """

    def insert_index(self):

        return None