"""provide an abstract class for external sources using a sqlite database helper

:organization: Logilab

:copyright: 2007-2009 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

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

"""

__docformat__ = "restructuredtext en"

import time

import threading

from os.path import join, exists

from cubicweb import server

from cubicweb.server.sqlutils import SQL_PREFIX, sqlexec, SQLAdapterMixIn

from cubicweb.server.sources import AbstractSource, native

from cubicweb.server.sources.rql2sql import SQLGenerator

def timeout_acquire(lock, timeout):

    while not lock.acquire(False):

        time.sleep(0.2)

        timeout -= 0.2

        if timeout <= 0:

            raise RuntimeError("svn source is busy, can't acquire connection lock")

class ConnectionWrapper(object):

    def __init__(self, source=None):

        self.source = source

        self._cnx = None

    @property

    def cnx(self):

        if self._cnx is None:

            timeout_acquire(self.source._cnxlock, 5)

            self._cnx = self.source._sqlcnx

        return self._cnx

    def commit(self):

        if self._cnx is not None:

            self._cnx.commit()

    def rollback(self):

        if self._cnx is not None:

            self._cnx.rollback()

    def cursor(self):

        return self.cnx.cursor()

class SQLiteAbstractSource(AbstractSource):

    """an abstract class for external sources using a sqlite database helper

    """

    sqlgen_class = SQLGenerator

    @classmethod

    def set_nonsystem_types(cls):

        # those entities are only in this source, we don't want them in the

        # system source

        for etype in cls.support_entities:

            native.NONSYSTEM_ETYPES.add(etype)

        for rtype in cls.support_relations:

            native.NONSYSTEM_RELATIONS.add(rtype)

    options = (

        ('helper-db-path',

         {'type' : 'string',

          'default': None,

          'help': 'path to the sqlite database file used to do queries on the \

repository.',

          'inputlevel': 2,

          }),

    )

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

        # the helper db is used to easy querying and will store everything but

        # actual file content

        dbpath = source_config.get('helper-db-path')

        if dbpath is None:

            dbpath = join(repo.config.appdatahome,

                          '%(uri)s.sqlite' % source_config)

        self.dbpath = dbpath

        self.sqladapter = SQLAdapterMixIn({'db-driver': 'sqlite',

                                           'db-name': dbpath})

        # those attributes have to be initialized before ancestor's __init__

        # which will call set_schema

        self._need_sql_create = not exists(dbpath)

        self._need_full_import = self._need_sql_create

        AbstractSource.__init__(self, repo, appschema, source_config,

                                *args, **kwargs)

        # sql database can only be accessed by one connection at a time, and a

        # connection can only be used by the thread which created it so:

        # * create the connection when needed

        # * use a lock to be sure only one connection is used

        self._cnxlock = threading.Lock()

    @property

    def _sqlcnx(self):

        # XXX: sqlite connections can only be used in the same thread, so

        #      create a new one each time necessary. If it appears to be time

        #      consuming, find another way

        return self.sqladapter.get_connection()

    def _is_schema_complete(self):

        for etype in self.support_entities:

            if not etype in self.schema:

                self.warning('not ready to generate %s database, %s support missing from schema',

                             self.uri, etype)

                return False

        for rtype in self.support_relations:

            if not rtype in self.schema:

                self.warning('not ready to generate %s database, %s support missing from schema',

                             self.uri, rtype)

                return False

        return True

    def _create_database(self):

        from yams.schema2sql import eschema2sql, rschema2sql

        from cubicweb.toolsutils import restrict_perms_to_user

        self.warning('initializing sqlite database for %s source' % self.uri)

        cnx = self._sqlcnx

        cu = cnx.cursor()

        schema = self.schema

        for etype in self.support_entities:

            eschema = schema.eschema(etype)

            createsqls = eschema2sql(self.sqladapter.dbhelper, eschema,

                                     skip_relations=('data',), prefix=SQL_PREFIX)

            sqlexec(createsqls, cu, withpb=False)

        for rtype in self.support_relations:

            rschema = schema.rschema(rtype)

            if not rschema.inlined:

                sqlexec(rschema2sql(rschema), cu, withpb=False)

        cnx.commit()

        cnx.close()

        self._need_sql_create = False

        if self.repo.config['uid']:

            from logilab.common.shellutils import chown

            # database file must be owned by the uid of the server process

            self.warning('set %s as owner of the database file',

                         self.repo.config['uid'])

            chown(self.dbpath, self.repo.config['uid'])

        restrict_perms_to_user(self.dbpath, self.info)

    def set_schema(self, schema):

        super(SQLiteAbstractSource, self).set_schema(schema)

        if self._need_sql_create and self._is_schema_complete() and self.dbpath:

            self._create_database()

        self.rqlsqlgen = self.sqlgen_class(schema, self.sqladapter.dbhelper)

    def get_connection(self):

        return ConnectionWrapper(self)

    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)

        always return the connection to reset eventually cached cursor

        """

        return cnx

    def pool_reset(self, cnx):

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

        attached session: release the connection lock if the connection wrapper

        has a connection set

        """

        if cnx._cnx is not None:

            try:

                cnx._cnx.close()

                cnx._cnx = None

            finally:

                self._cnxlock.release()

    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.

        """

        if self._need_sql_create:

            return []

        sql, query_args = self.rqlsqlgen.generate(union, args)

        if server.DEBUG:

            print self.uri, 'SOURCE RQL', union.as_string()

            print 'GENERATED SQL', sql

        args = self.sqladapter.merge_args(args, query_args)

        cursor = session.pool[self.uri]

        cursor.execute(sql, args)

        return self.sqladapter.process_result(cursor)

    def local_add_entity(self, session, entity):

        """insert the entity in the local database.

        This is not provided as add_entity implementation since usually source

        don't want to simply do this, so let raise NotImplementedError and the

        source implementor may use this method if necessary

        """

        cu = session.pool[self.uri]

        attrs = self.sqladapter.preprocess_entity(entity)

        sql = self.sqladapter.sqlgen.insert(SQL_PREFIX + str(entity.e_schema), attrs)

        cu.execute(sql, attrs)

    def add_entity(self, session, entity):

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

        raise NotImplementedError()

    def local_update_entity(self, session, entity, attrs=None):

        """update an entity in the source

        This is not provided as update_entity implementation since usually

        source don't want to simply do this, so let raise NotImplementedError

        and the source implementor may use this method if necessary

        """

        cu = session.pool[self.uri]

        if attrs is None:

            attrs = self.sqladapter.preprocess_entity(entity)

        sql = self.sqladapter.sqlgen.update(SQL_PREFIX + str(entity.e_schema),

                                            attrs, [SQL_PREFIX + 'eid'])

        cu.execute(sql, attrs)

    def update_entity(self, session, entity):

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

        raise NotImplementedError()

    def delete_entity(self, session, etype, eid):

        """delete an entity from the source

        this is not deleting a file in the svn but deleting entities from the

        source. Main usage is to delete repository content when a Repository

        entity is deleted.

        """

        sqlcursor = session.pool[self.uri]

        attrs = {SQL_PREFIX + 'eid': eid}

        sql = self.sqladapter.sqlgen.delete(SQL_PREFIX + etype, attrs)

        sqlcursor.execute(sql, attrs)

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

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

        rschema = self.schema.rschema(rtype)

        if rschema.inlined:

            if subject in session.query_data('pendingeids', ()):

                return

            table = SQL_PREFIX + session.describe(subject)[0]

            column = SQL_PREFIX + rtype

            sql = 'UPDATE %s SET %s=NULL WHERE %seid=%%(eid)s' % (table, column, SQL_PREFIX)

            attrs = {'eid' : subject}

        else:

            attrs = {'eid_from': subject, 'eid_to': object}

            sql = self.sqladapter.sqlgen.delete('%s_relation' % rtype, attrs)

        sqlcursor = session.pool[self.uri]

        sqlcursor.execute(sql, attrs)