# Copyright (C) 2006-2012 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman 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 General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.

from __future__ import absolute_import, unicode_literals

__metaclass__ = type
__all__ = [
    'StormBaseDatabase',
    ]


import os
import logging

from flufl.lock import Lock
from lazr.config import as_boolean
from storm.cache import GenerationalCache
from storm.locals import create_database, Store
from zope.interface import implements

import mailman.version

from mailman.config import config
from mailman.interfaces.database import IDatabase, SchemaVersionMismatchError
from mailman.model.version import Version
from mailman.utilities.string import expand

log = logging.getLogger('mailman.config')

NL = '\n'



class StormBaseDatabase:
    """The database base class for use with the Storm ORM.

    Use this as a base class for your DB-specific derived classes.
    """

    implements(IDatabase)

    def __init__(self):
        self.url = None
        self.store = None

    def initialize(self, debug=None):
        """See `IDatabase`."""
        # Serialize this so we don't get multiple processes trying to create
        # the database at the same time.
        with Lock(os.path.join(config.LOCK_DIR, 'dbcreate.lck')):
            self._create(debug)

    def begin(self):
        """See `IDatabase`."""
        # Storm takes care of this for us.
        pass

    def commit(self):
        """See `IDatabase`."""
        self.store.commit()

    def abort(self):
        """See `IDatabase`."""
        self.store.rollback()

    def _database_exists(self):
        """Return True if the database exists and is initialized.

        Return False when Mailman needs to create and initialize the
        underlying database schema.

        Base classes *must* override this.
        """
        raise NotImplementedError

    def _get_schema(self):
        """Return the database schema as a string.

        This will be loaded into the database when it is first created.

        Base classes *must* override this.
        """
        raise NotImplementedError

    def _pre_reset(self, store):
        """Clean up method for testing.

        This method is called during the test suite just before all the model
        tables are removed.  Override this to perform any database-specific
        pre-removal cleanup.
        """
        pass

    def _post_reset(self, store):
        """Clean up method for testing.

        This method is called during the test suite just after all the model
        tables have been removed.  Override this to perform any
        database-specific post-removal cleanup.
        """
        pass

    def _prepare(self, url):
        """Prepare the database for creation.

        Some database backends need to do so me prep work before letting Storm
        create the database.  For example, we have to touch the SQLite .db
        file first so that it has the proper file modes.
        """
        pass

    def _create(self, debug):
        # Calculate the engine url.
        url = expand(config.database.url, config.paths)
        log.debug('Database url: %s', url)
        # XXX By design of SQLite, database file creation does not honor
        # umask.  See their ticket #1193:
        # http://www.sqlite.org/cvstrac/tktview?tn=1193,31
        #
        # This sucks for us because the mailman.db file /must/ be group
        # writable, however even though we guarantee our umask is 002 here, it
        # still gets created without the necessary g+w permission, due to
        # SQLite's policy.  This should only affect SQLite engines because its
        # the only one that creates a little file on the local file system.
        # This kludges around their bug by "touch"ing the database file before
        # SQLite has any chance to create it, thus honoring the umask and
        # ensuring the right permissions.  We only try to do this for SQLite
        # engines, and yes, we could have chmod'd the file after the fact, but
        # half dozen and all...
        self.url = url
        self._prepare(url)
        database = create_database(url)
        store = Store(database, GenerationalCache())
        database.DEBUG = (as_boolean(config.database.debug)
                          if debug is None else debug)
        # Check the master / schema database to see if the version table
        # exists.  If so, then we assume the database schema is correctly
        # initialized.  Storm does not currently provide schema creation.
        if not self._database_exists(store):
            # Initialize the database.  Start by getting the schema and
            # discarding all blank and comment lines.
            lines = self._get_schema().splitlines()
            lines = (line for line in lines
                     if line.strip() != '' and line.strip()[:2] != '--')
            sql = NL.join(lines)
            for statement in sql.split(';'):
                if statement.strip() != '':
                    store.execute(statement + ';')
        # Validate schema version.
        v = store.find(Version, component='schema').one()
        if not v:
            # Database has not yet been initialized
            v = Version(component='schema',
                        version=mailman.version.DATABASE_SCHEMA_VERSION)
            store.add(v)
        elif v.version <> mailman.version.DATABASE_SCHEMA_VERSION:
            # XXX Update schema
            raise SchemaVersionMismatchError(v.version)
        self.store = store
        store.commit()

    def _reset(self):
        """See `IDatabase`."""
        from mailman.database.model import ModelMeta
        self.store.rollback()
        ModelMeta._reset(self.store)