# Copyright 2012 New Dream Network, LLC (DreamHost)
#
#    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 os

from alembic import command as alembic_command
from alembic import config as alembic_config
from alembic import script as alembic_script
from alembic import util as alembic_util
from oslo_config import cfg

HEAD_FILENAME = 'HEAD'


_db_opts = [
    cfg.StrOpt('connection',
               deprecated_name='sql_connection',
               default='',
               secret=True,
               help=_('URL to database')),
    cfg.StrOpt('engine',
               default='',
               help=_('Database engine')),
]

CONF = cfg.ConfigOpts()
CONF.register_cli_opts(_db_opts, 'database')


def do_alembic_command(config, cmd, *args, **kwargs):
    try:
        getattr(alembic_command, cmd)(config, *args, **kwargs)
    except alembic_util.CommandError as e:
        alembic_util.err(str(e))


def do_check_migration(config, cmd):
    do_alembic_command(config, 'branches')
    validate_head_file(config)


def do_upgrade_downgrade(config, cmd):
    if not CONF.command.revision and not CONF.command.delta:
        raise SystemExit(_('You must provide a revision or relative delta'))

    revision = CONF.command.revision

    if CONF.command.delta:
        sign = '+' if CONF.command.name == 'upgrade' else '-'
        revision = sign + str(CONF.command.delta)
    else:
        revision = CONF.command.revision

    do_alembic_command(config, cmd, revision, sql=CONF.command.sql)


def do_stamp(config, cmd):
    do_alembic_command(config, cmd,
                       CONF.command.revision,
                       sql=CONF.command.sql)


def do_revision(config, cmd):
    do_alembic_command(config, cmd,
                       message=CONF.command.message,
                       autogenerate=CONF.command.autogenerate,
                       sql=CONF.command.sql)
    update_head_file(config)


def validate_head_file(config):
    script = alembic_script.ScriptDirectory.from_config(config)
    if len(script.get_heads()) > 1:
        alembic_util.err(_('Timeline branches unable to generate timeline'))

    head_path = os.path.join(script.versions, HEAD_FILENAME)
    if (os.path.isfile(head_path) and
            open(head_path).read().strip() == script.get_current_head()):
        return
    else:
        alembic_util.err(_('HEAD file does not match migration timeline head'))


def update_head_file(config):
    script = alembic_script.ScriptDirectory.from_config(config)
    if len(script.get_heads()) > 1:
        alembic_util.err(_('Timeline branches unable to generate timeline'))

    head_path = os.path.join(script.versions, HEAD_FILENAME)
    with open(head_path, 'w+') as f:
        f.write(script.get_current_head())


def add_command_parsers(subparsers):
    for name in ['current', 'history', 'branches']:
        parser = subparsers.add_parser(name)
        parser.set_defaults(func=do_alembic_command)

    parser = subparsers.add_parser('check_migration')
    parser.set_defaults(func=do_check_migration)

    for name in ['upgrade', 'downgrade']:
        parser = subparsers.add_parser(name)
        parser.add_argument('--delta', type=int)
        parser.add_argument('--sql', action='store_true')
        parser.add_argument('revision', nargs='?')
        parser.add_argument('--mysql-engine',
                            default='',
                            help='Change MySQL storage engine of current '
                                 'existing tables')
        parser.set_defaults(func=do_upgrade_downgrade)

    parser = subparsers.add_parser('stamp')
    parser.add_argument('--sql', action='store_true')
    parser.add_argument('revision')
    parser.set_defaults(func=do_stamp)

    parser = subparsers.add_parser('revision')
    parser.add_argument('-m', '--message')
    parser.add_argument('--autogenerate', action='store_true')
    parser.add_argument('--sql', action='store_true')
    parser.set_defaults(func=do_revision)


command_opt = cfg.SubCommandOpt('command',
                                title='Command',
                                help=_('Available commands'),
                                handler=add_command_parsers)

CONF.register_cli_opt(command_opt)


def main():
    config = alembic_config.Config(
        os.path.join(os.path.dirname(__file__), 'alembic.ini')
    )
    config.set_main_option('script_location',
                           'congress.db.migration:alembic_migrations')
    # attach the Neutron conf to the Alembic conf
    config.congress_config = CONF

    CONF()
    # TODO(gongysh) enable logging
    CONF.command.func(config, CONF.command.name)
