"""Create a consistent SQLite backup without copying a live database file."""
import argparse
import os
import sqlite3
from datetime import datetime
from pathlib import Path


def backup_database(data_dir):
    instance = Path(data_dir).resolve() / 'instance'
    source = instance / 'po.db'
    if not source.is_file():
        raise FileNotFoundError('未找到数据库：%s' % source)
    destination_dir = instance / 'backups'
    destination_dir.mkdir(exist_ok=True)
    destination = destination_dir / ('po-' + datetime.now().strftime('%Y%m%d-%H%M%S-%f') + '.db')
    with sqlite3.connect(source.as_uri() + '?mode=ro', uri=True) as original:
        with sqlite3.connect(destination) as copy:
            original.backup(copy)
            if copy.execute('PRAGMA integrity_check').fetchone()[0] != 'ok':
                raise RuntimeError('备份完整性检查未通过：%s' % destination)
    return destination


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--data-dir', default=os.environ.get('PO_DATA_DIR', str(Path(__file__).resolve().parents[1] / 'po_app')))
    args = parser.parse_args()
    print(backup_database(args.data_dir))