# Copyright (C) 2006-2014 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, print_function, unicode_literals

__metaclass__ = type
__all__ = [
    'SABaseDatabase',
    ]


import logging

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from zope.interface import implementer

from mailman.config import config
from mailman.interfaces.database import IDatabase
from mailman.utilities.string import expand


log = logging.getLogger('mailman.config')
NL = '\n'



@implementer(IDatabase)
class SABaseDatabase:
    """The database base class for use with SQLAlchemy.

    Use this as a base class for your DB-Specific derived classes.
    """
    # Tag used to distinguish the database being used.  Override this in base
    # classes.
    TAG = ''

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

    def begin(self):
        """See `IDatabase`."""
        # SQLAlchemy does 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 _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

    # XXX Abhilash removed teh _prepare() method.  Is that because SA takes
    # care of this for us?  If so, then the comment below must be updated.
    # For reference, the SQLite bug is marked "won't fix".

    def initialize(self, debug=None):
        """See `IDatabase`."""
        # Calculate the engine url.
        url = expand(config.database.url, config.paths)
        self._prepare(url)
        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.engine = create_engine(url)
        session = sessionmaker(bind=self.engine)
        self.store = session()
        self.store.commit()

    # XXX We should probably rename load_migrations() and perhaps get rid of
    # load_sql().  The latter is never called any more.

    def load_migrations(self, until=None):
        """Load schema migrations.

        :param until: Load only the migrations up to the specified timestamp.
            With default value of None, load all migrations.
        :type until: string
        """
        from mailman.database.model import Model
        Model.metadata.create_all(self.engine)

    def load_sql(self, store, sql):
        """Load the given SQL into the store.

        :param store: The Storm store to load the schema into.
        :type store: storm.locals.Store`
        :param sql: The possibly multi-line SQL to load.
        :type sql: string
        """
        # Discard all blank and comment lines.
        lines = (line for line in sql.splitlines()
                 if line.strip() != '' and line.strip()[:2] != '--')
        sql = NL.join(lines)
        for statement in sql.split(';'):
            if statement.strip() != '':
                store.execute(statement + ';')


    @staticmethod
    def _make_temporary():
        raise NotImplementedError