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  #
  # Copyright 2011 Rackspace
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  import logging
  import os
  
  from tempo import config
  
  from migrate.versioning import api as versioning_api
  
  # See LP bug #719834. sqlalchemy-migrate changed location of
  # exceptions.py after 0.6.0.
  try:
      from migrate.versioning import exceptions as versioning_exceptions
  except ImportError:
      from migrate import exceptions as versioning_exceptions
  
  logger = logging.getLogger('tempo.db.migration')
  
  CFG = config.CFG
  
  
  class DatabaseMigrationError(Exception):
      pass
  
  
  def db_version():
      """Return the database's current migration number."""
      repo_path = get_migrate_repo_path()
      sql_connection = CFG.db.sql_connection
      try:
          return versioning_api.db_version(sql_connection, repo_path)
      except versioning_exceptions.DatabaseNotControlledError, e:
          msg = ("database '%(sql_connection)s' is not under migration control"
                 % locals())
          raise DatabaseMigrationError(msg)
  
  
  def upgrade(version=None):
      """Upgrade the database's current migration level."""
      db_version()  # Ensure db is under migration control
      repo_path = get_migrate_repo_path()
      sql_connection = CFG.db.sql_connection
      version_str = version or 'latest'
      logger.info("Upgrading %(sql_connection)s to version %(version_str)s" %
                  locals())
      return versioning_api.upgrade(sql_connection, repo_path, version)
  
  
  def downgrade(version):
      """Downgrade the database's current migration level."""
      db_version()  # Ensure db is under migration control
      repo_path = get_migrate_repo_path()
      sql_connection = CFG.db.sql_connection
      logger.info("Downgrading %(sql_connection)s to version %(version)s" %
                  locals())
      return versioning_api.downgrade(sql_connection, repo_path, version)
  
  
  def version_control():
      """Place a database under migration control."""
      sql_connection = CFG.db.sql_connection
      try:
          versioning_api.version_control(
                  CFG.sql_connection, get_migrate_repo_path())
      except versioning_exceptions.DatabaseAlreadyControlledError, e:
          msg = ("database '%(sql_connection)s' is already under migration "
                 "control" % locals())
          raise DatabaseMigrationError(msg)
  
  
  def db_sync(version=None):
      """Place a database under migration control and perform an upgrade."""
      try:
          versioning_api.version_control(
              CFG.db.sql_connection, get_migrate_repo_path())
      except versioning_exceptions.DatabaseAlreadyControlledError, e:
          pass
  
      upgrade(version=version)
  
  
  def get_migrate_repo_path():
      """Get the path for the migrate repository."""
      path = os.path.join(os.path.abspath(os.path.dirname(__file__)),
                          'migrate_repo')
      assert os.path.exists(path)
      return path
  