#!/usr/bin/python -u

import os, sys, re, subprocess, tempfile
import MySQLdb, MySQLdb.constants.ER
from optparse import OptionParser
import common
from autotest_lib.client.common_lib import global_config
from autotest_lib.database import database_connection

MIGRATE_TABLE = 'migrate_info'

_AUTODIR = os.path.join(os.path.dirname(__file__), '..')
_MIGRATIONS_DIRS = {
    'AUTOTEST_WEB' : os.path.join(_AUTODIR, 'frontend', 'migrations'),
    'TKO' : os.path.join(_AUTODIR, 'tko', 'migrations'),
}
_DEFAULT_MIGRATIONS_DIR = 'migrations' # use CWD

class Migration(object):
    def __init__(self, filename):
        self.version = int(filename[:3])
        self.name = filename[:-3]
        self.module = __import__(self.name, globals(), locals(), [])
        assert hasattr(self.module, 'migrate_up')
        assert hasattr(self.module, 'migrate_down')


    def migrate_up(self, manager):
        self.module.migrate_up(manager)


    def migrate_down(self, manager):
        self.module.migrate_down(manager)


class MigrationManager(object):
    connection = None
    cursor = None
    migrations_dir = None

    def __init__(self, database_connection, migrations_dir=None, force=False):
        self._database = database_connection
        self.force = force
        self._set_migrations_dir(migrations_dir)


    def _set_migrations_dir(self, migrations_dir=None):
        config_section = self._database.global_config_section
        if migrations_dir is None:
            migrations_dir = os.path.abspath(
                _MIGRATIONS_DIRS.get(config_section, _DEFAULT_MIGRATIONS_DIR))
        self.migrations_dir = migrations_dir
        sys.path.append(migrations_dir)
        assert os.path.exists(migrations_dir), migrations_dir + " doesn't exist"


    def _get_db_name(self):
        return self._database.get_database_info()['db_name']


    def execute(self, query, *parameters):
        return self._database.execute(query, parameters)


    def execute_script(self, script):
        sql_statements = [statement.strip()
                          for statement in script.split(';')
                          if statement.strip()]
        for statement in sql_statements:
            self.execute(statement)


    def check_migrate_table_exists(self):
        try:
            self.execute("SELECT * FROM %s" % MIGRATE_TABLE)
            return True
        except self._database.DatabaseError, exc:
            # we can't check for more specifics due to differences between DB
            # backends (we can't even check for a subclass of DatabaseError)
            return False


    def create_migrate_table(self):
        if not self.check_migrate_table_exists():
            self.execute("CREATE TABLE %s (`version` integer)" %
                         MIGRATE_TABLE)
        else:
            self.execute("DELETE FROM %s" % MIGRATE_TABLE)
        self.execute("INSERT INTO %s VALUES (0)" % MIGRATE_TABLE)
        assert self._database.rowcount == 1


    def set_db_version(self, version):
        assert isinstance(version, int)
        self.execute("UPDATE %s SET version=%%s" % MIGRATE_TABLE,
                     version)
        assert self._database.rowcount == 1


    def get_db_version(self):
        if not self.check_migrate_table_exists():
            return 0
        rows = self.execute("SELECT * FROM %s" % MIGRATE_TABLE)
        if len(rows) == 0:
            return 0
        assert len(rows) == 1 and len(rows[0]) == 1
        return rows[0][0]


    def get_migrations(self, minimum_version=None, maximum_version=None):
        migrate_files = [filename for filename
                         in os.listdir(self.migrations_dir)
                         if re.match(r'^\d\d\d_.*\.py$', filename)]
        migrate_files.sort()
        migrations = [Migration(filename) for filename in migrate_files]
        if minimum_version is not None:
            migrations = [migration for migration in migrations
                          if migration.version >= minimum_version]
        if maximum_version is not None:
            migrations = [migration for migration in migrations
                          if migration.version <= maximum_version]
        return migrations


    def do_migration(self, migration, migrate_up=True):
        print 'Applying migration %s' % migration.name, # no newline
        if migrate_up:
            print 'up'
            assert self.get_db_version() == migration.version - 1
            migration.migrate_up(self)
            new_version = migration.version
        else:
            print 'down'
            assert self.get_db_version() == migration.version
            migration.migrate_down(self)
            new_version = migration.version - 1
        self.set_db_version(new_version)


    def migrate_to_version(self, version):
        current_version = self.get_db_version()
        if current_version < version:
            lower, upper = current_version, version
            migrate_up = True
        else:
            lower, upper = version, current_version
            migrate_up = False

        migrations = self.get_migrations(lower + 1, upper)
        if not migrate_up:
            migrations.reverse()
        for migration in migrations:
            self.do_migration(migration, migrate_up)

        assert self.get_db_version() == version
        print 'At version', version


    def get_latest_version(self):
        migrations = self.get_migrations()
        return migrations[-1].version


    def migrate_to_latest(self):
        latest_version = self.get_latest_version()
        self.migrate_to_version(latest_version)


    def initialize_test_db(self):
        db_name = self._get_db_name()
        test_db_name = 'test_' + db_name
        # first, connect to no DB so we can create a test DB
        self._database.connect(db_name='')
        print 'Creating test DB', test_db_name
        self.execute('CREATE DATABASE ' + test_db_name)
        self._database.disconnect()
        # now connect to the test DB
        self._database.connect(db_name=test_db_name)


    def remove_test_db(self):
        print 'Removing test DB'
        self.execute('DROP DATABASE ' + self._get_db_name())
        # reset connection back to real DB
        self._database.disconnect()
        self._database.connect()


    def get_mysql_args(self):
        return ('-u %(username)s -p%(password)s -h %(host)s %(db_name)s' %
                self._database.get_database_info())


    def migrate_to_version_or_latest(self, version):
        if version is None:
            self.migrate_to_latest()
        else:
            self.migrate_to_version(version)


    def do_sync_db(self, version=None):
        print 'Migration starting for database', self._get_db_name()
        self.migrate_to_version_or_latest(version)
        print 'Migration complete'


    def test_sync_db(self, version=None):
        """\
        Create a fresh DB and run all migrations on it.
        """
        self.initialize_test_db()
        try:
            print 'Starting migration test on DB', self._get_db_name()
            self.migrate_to_version_or_latest(version)
            # show schema to the user
            os.system('mysqldump %s --no-data=true '
                      '--add-drop-table=false' %
                      self.get_mysql_args())
        finally:
            self.remove_test_db()
        print 'Test finished successfully'


    def simulate_sync_db(self, version=None):
        """\
        Create a fresh DB, copy the existing DB to it, and then
        try to synchronize it.
        """
        db_version = self.get_db_version()
        # don't do anything if we're already at the latest version
        if db_version == self.get_latest_version():
            print 'Skipping simulation, already at latest version'
            return
        # get existing data
        print 'Dumping existing data'
        dump_fd, dump_file = tempfile.mkstemp('.migrate_dump')
        os.system('mysqldump %s >%s' %
                  (self.get_mysql_args(), dump_file))
        # fill in test DB
        self.initialize_test_db()
        print 'Filling in test DB'
        os.system('mysql %s <%s' % (self.get_mysql_args(), dump_file))
        os.close(dump_fd)
        os.remove(dump_file)
        try:
            print 'Starting migration test on DB', self._get_db_name()
            self.migrate_to_version_or_latest(version)
        finally:
            self.remove_test_db()
        print 'Test finished successfully'


USAGE = """\
%s [options] sync|test|simulate|safesync [version]
Options:
    -d --database   Which database to act on
    -a --action     Which action to perform"""\
    % sys.argv[0]


def main():
    parser = OptionParser()
    parser.add_option("-d", "--database",
                      help="which database to act on",
                      dest="database")
    parser.add_option("-a", "--action", help="what action to perform",
                      dest="action")
    parser.add_option("-f", "--force", help="don't ask for confirmation",
                      action="store_true")
    (options, args) = parser.parse_args()
    database = database_connection.DatabaseConnection(options.database)
    database.reconnect_enabled = False
    database.connect()
    manager = MigrationManager(database, force=options.force)

    if len(args) > 0:
        if len(args) > 1:
            version = int(args[1])
        else:
            version = None
        if args[0] == 'sync':
            manager.do_sync_db(version)
        elif args[0] == 'test':
            manager.test_sync_db(version)
        elif args[0] == 'simulate':
            manager.simulate_sync_db(version)
        elif args[0] == 'safesync':
            print 'Simluating migration'
            manager.simulate_sync_db(version)
            print 'Performing real migration'
            manager.do_sync_db(version)
        else:
            print USAGE
        return

    print USAGE


if __name__ == '__main__':
    main()