# copyright 2003-2010 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/>.

"""cubicweb server sources support"""

__docformat__ = "restructuredtext en"

from os.path import join, splitext

from datetime import datetime, timedelta

from logging import getLogger

from cubicweb import set_log_methods, server

from cubicweb.schema import VIRTUAL_RTYPES

from cubicweb.server.sqlutils import SQL_PREFIX

from cubicweb.server.ssplanner import EditedEntity

def dbg_st_search(uri, union, varmap, args, cachekey=None, prefix='rql for'):

    if server.DEBUG & server.DBG_RQL:

        print '  %s %s source: %s' % (prefix, uri, union.as_string())

        if varmap:

            print '    using varmap', varmap

        if server.DEBUG & server.DBG_MORE:

            print '    args', args

            print '    cache key', cachekey

            print '    solutions', ','.join(str(s.solutions)

                                            for s in union.children)

    # return true so it can be used as assertion (and so be killed by python -O)

    return True

def dbg_results(results):

    if server.DEBUG & server.DBG_RQL:

        if len(results) > 10:

            print '  -->', results[:10], '...', len(results)

        else:

            print '  -->', results

    # return true so it can be used as assertion (and so be killed by python -O)

    return True

class TimedCache(dict):

    def __init__(self, ttl):

        # time to live in seconds

        if ttl <= 0:

            raise ValueError('TimedCache initialized with a ttl of %ss' % ttl.seconds)

        self.ttl = timedelta(seconds=ttl)

    def __setitem__(self, key, value):

        dict.__setitem__(self, key, (datetime.now(), value))

    def __getitem__(self, key):

        return dict.__getitem__(self, key)[1]

    def clear_expired(self):

        now_ = datetime.now()

        ttl = self.ttl

        for key, (timestamp, value) in self.items():

            if now_ - timestamp > ttl:

                del self[key]

class AbstractSource(object):

    """an abstract class for sources"""

    # boolean telling if modification hooks should be called when something is

    # modified in this source

    should_call_hooks = True

    # boolean telling if the repository should connect to this source during

    # migration

    connect_for_migration = True

    # mappings telling which entities and relations are available in the source

    # keys are supported entity/relation types and values are boolean indicating

    # wether the support is read-only (False) or read-write (True)

    support_entities = {}

    support_relations = {}

    # a global identifier for this source, which has to be set by the source

    # instance

    uri = None

    # a reference to the system information helper

    repo = None

    # a reference to the instance'schema (may differs from the source'schema)

    schema = None

    # multi-sources planning control

    dont_cross_relations = ()

    cross_relations = ()

    # force deactivation (configuration error for instance)

    disabled = False

    def __init__(self, repo, source_config, *args, **kwargs):

        self.repo = repo

        self.uri = source_config['uri']

        set_log_methods(self, getLogger('cubicweb.sources.'+self.uri))

        self.set_schema(repo.schema)

        self.support_relations['identity'] = False

        self.eid = None

        self.public_config = source_config.copy()

        self.remove_sensitive_information(self.public_config)

    def init_creating(self):

        """method called by the repository once ready to create a new instance"""

        pass

    def init(self):

        """method called by the repository once ready to handle request"""

        pass

    def backup(self, backupfile, confirm):

        """method called to create a backup of source's data"""

        pass

    def restore(self, backupfile, confirm, drop):

        """method called to restore a backup of source's data"""

        pass

    def close_pool_connections(self):

        for pool in self.repo.pools:

            pool._cursors.pop(self.uri, None)

            pool.source_cnxs[self.uri][1].close()

    def open_pool_connections(self):

        for pool in self.repo.pools:

            pool.source_cnxs[self.uri] = (self, self.get_connection())

    def reset_caches(self):

        """method called during test to reset potential source caches"""

        pass

    def clear_eid_cache(self, eid, etype):

        """clear potential caches for the given eid"""

        pass

    def __repr__(self):

        return '<%s source @%#x>' % (self.uri, id(self))

    def __cmp__(self, other):

        """simple comparison function to get predictable source order, with the

        system source at last

        """

        if self.uri == other.uri:

            return 0

        if self.uri == 'system':

            return 1

        if other.uri == 'system':

            return -1

        return cmp(self.uri, other.uri)

    def set_schema(self, schema):

        """set the instance'schema"""

        self.schema = schema

    def support_entity(self, etype, write=False):

        """return true if the given entity's type is handled by this adapter

        if write is true, return true only if it's a RW support

        """

        try:

            wsupport = self.support_entities[etype]

        except KeyError:

            return False

        if write:

            return wsupport

        return True

    def support_relation(self, rtype, write=False):

        """return true if the given relation's type is handled by this adapter

        if write is true, return true only if it's a RW support

        current implementation return true if the relation is defined into

        `support_relations` or if it is a final relation of a supported entity

        type

        """

        try:

            wsupport = self.support_relations[rtype]

        except KeyError:

            rschema = self.schema.rschema(rtype)

            if not rschema.final or rschema.type == 'has_text':

                return False

            for etype in rschema.subjects():

                try:

                    wsupport = self.support_entities[etype]

                    break

                except KeyError:

                    continue

            else:

                return False

        if write:

            return wsupport

        return True

    def may_cross_relation(self, rtype):

        """return True if the relation may be crossed among sources. Rules are:

        * if this source support the relation, can't be crossed unless explicitly

          specified in .cross_relations

        * if this source doesn't support the relation, can be crossed unless

          explicitly specified in .dont_cross_relations

        """

        # XXX find a way to have relation such as state_of in dont cross

        #     relation (eg composite relation without both end type available?

        #     card 1 relation ? ...)

        if self.support_relation(rtype):

            return rtype in self.cross_relations

        return rtype not in self.dont_cross_relations

    def eid2extid(self, eid, session=None):

        return self.repo.eid2extid(self, eid, session)

    def extid2eid(self, value, etype, session=None, **kwargs):

        return self.repo.extid2eid(self, value, etype, session, **kwargs)

    PUBLIC_KEYS = ('type', 'uri')

    def remove_sensitive_information(self, sourcedef):

        """remove sensitive information such as login / password from source

        definition

        """

        for key in sourcedef.keys():

            if not key in self.PUBLIC_KEYS:

                sourcedef.pop(key)

    def _cleanup_system_relations(self, session):

        """remove relation in the system source referencing entities coming from

        this source

        """

        cu = session.system_sql('SELECT eid FROM entities WHERE source=%(uri)s',

                                {'uri': self.uri})

        myeids = ','.join(str(r[0]) for r in cu.fetchall())

        if not myeids:

            return

        # delete relations referencing one of those eids

        eidcolum = SQL_PREFIX + 'eid'

        for rschema in self.schema.relations():

            if rschema.final or rschema.type in VIRTUAL_RTYPES:

                continue

            if rschema.inlined:

                column = SQL_PREFIX + rschema.type

                for subjtype in rschema.subjects():

                    table = SQL_PREFIX + str(subjtype)

                    for objtype in rschema.objects(subjtype):

                        if self.support_entity(objtype):

                            sql = 'UPDATE %s SET %s=NULL WHERE %s IN (%s);' % (

                                table, column, eidcolum, myeids)

                            session.system_sql(sql)

                            break

                continue

            for etype in rschema.subjects():

                if self.support_entity(etype):

                    sql = 'DELETE FROM %s_relation WHERE eid_from IN (%s);' % (

                        rschema.type, myeids)

                    session.system_sql(sql)

                    break

            for etype in rschema.objects():

                if self.support_entity(etype):

                    sql = 'DELETE FROM %s_relation WHERE eid_to IN (%s);' % (

                        rschema.type, myeids)

                    session.system_sql(sql)

                    break

    def cleanup_entities_info(self, session):

        """cleanup system tables from information for entities coming from

        this source. This should be called when a source is removed to

        properly cleanup the database

        """

        self._cleanup_system_relations(session)

        # fti / entities tables cleanup

        # sqlite doesn't support DELETE FROM xxx USING yyy

        dbhelper = session.pool.source('system').dbhelper

        session.system_sql('DELETE FROM %s WHERE %s.%s IN (SELECT eid FROM '

                           'entities WHERE entities.source=%%(uri)s)'

                           % (dbhelper.fti_table, dbhelper.fti_table,

                              dbhelper.fti_uid_attr),

                           {'uri': self.uri})

        session.system_sql('DELETE FROM entities WHERE source=%(uri)s',

                           {'uri': self.uri})

    # abstract methods to override (at least) in concrete source classes #######

    def get_connection(self):

        """open and return a connection to the source"""

        raise NotImplementedError()

    def check_connection(self, cnx):

        """check connection validity, return None if the connection is still valid

        else a new connection (called when the pool using the given connection is

        being attached to a session)

        do nothing by default

        """

        pass

    def pool_reset(self, cnx):

        """the pool using the given connection is being reseted from its current

        attached session

        do nothing by default

        """

        pass

    def authenticate(self, session, login, **kwargs):

        """if the source support CWUser entity type, it should implement

        this method which should return CWUser eid for the given login/password

        if this account is defined in this source and valid login / password is

        given. Else raise `AuthenticationError`

        """

        raise NotImplementedError()

    def syntax_tree_search(self, session, union,

                           args=None, cachekey=None, varmap=None, debug=0):

        """return result from this source for a rql query (actually from a rql

        syntax tree and a solution dictionary mapping each used variable to a

        possible type). If cachekey is given, the query necessary to fetch the

        results (but not the results themselves) may be cached using this key.

        """

        raise NotImplementedError()

    def flying_insert(self, table, session, union, args=None, varmap=None):

        """similar as .syntax_tree_search, but inserts data in the temporary

        table (on-the-fly if possible, eg for the system source whose the given

        cursor come from). If not possible, inserts all data by calling

        .executemany().

        """

        res = self.syntax_tree_search(session, union, args, varmap=varmap)

        session.pool.source('system').manual_insert(res, table, session)

    # system source don't have to implement the two methods below

    def before_entity_insertion(self, session, lid, etype, eid):

        """called by the repository when an eid has been attributed for an

        entity stored here but the entity has not been inserted in the system

        table yet.

        This method must return the an Entity instance representation of this

        entity.

        """

        entity = self.repo.vreg['etypes'].etype_class(etype)(session)

        entity.eid = eid

        entity.cw_edited = EditedEntity(entity)

        return entity

    def after_entity_insertion(self, session, lid, entity):

        """called by the repository after an entity stored here has been

        inserted in the system table.

        """

        pass

    # read-only sources don't have to implement methods below

    def get_extid(self, entity):

        """return the external id for the given newly inserted entity"""

        raise NotImplementedError()

    def add_entity(self, session, entity):

        """add a new entity to the source"""

        raise NotImplementedError()

    def update_entity(self, session, entity):

        """update an entity in the source"""

        raise NotImplementedError()

    def delete_entity(self, session, entity):

        """delete an entity from the source"""

        raise NotImplementedError()

    def add_relation(self, session, subject, rtype, object):

        """add a relation to the source"""

        raise NotImplementedError()

    def delete_relation(self, session, subject, rtype, object):

        """delete a relation from the source"""

        raise NotImplementedError()

    # system source interface #################################################

    def eid_type_source(self, session, eid):

        """return a tuple (type, source, extid) for the entity with id <eid>"""

        raise NotImplementedError()

    def create_eid(self, session):

        raise NotImplementedError()

    def add_info(self, session, entity, source, extid):

        """add type and source info for an eid into the system table"""

        raise NotImplementedError()