#!/usr/bin/env python3
"""Backup the SQLite database used by TakeYourMeds.

Usage:
    python tools/backup_db.py [destination_dir]

Defaults to ./data/backups/ and keeps the last 14 backups.
"""
from __future__ import annotations

import argparse
import gzip
import logging
import pathlib
import shutil
import sys
from datetime import UTC, datetime

from server.settings import settings

logger = logging.getLogger(__name__)
logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")

DEFAULT_KEEP = 14


def backup_db(destination: pathlib.Path | None = None, keep: int = DEFAULT_KEEP) -> pathlib.Path:
    src = pathlib.Path(settings.db_path)
    if not src.exists():
        raise FileNotFoundError(f"Database not found: {src}")

    dest_dir = destination or pathlib.Path(src.parent) / "backups"
    dest_dir.mkdir(parents=True, exist_ok=True)

    timestamp = datetime.now(UTC).strftime("%Y%m%dT%H%M%SZ")
    dest_file = dest_dir / f"medis-{timestamp}.sqlite.gz"

    # SQLite backup via online copy is safe because WAL is not enabled by default.
    # For guaranteed consistency under writes, use the backup API.
    import aiosqlite

    async def _copy() -> None:
        async with (
            aiosqlite.connect(str(src)) as src_db,
            aiosqlite.connect(str(dest_file).replace(".gz", "")) as dst_db,
        ):
            await src_db.backup(dst_db)

    import asyncio

    plain = dest_file.with_suffix("")
    asyncio.run(_copy())

    with open(plain, "rb") as f_in, gzip.open(dest_file, "wb") as f_out:
        shutil.copyfileobj(f_in, f_out)
    plain.unlink()

    logger.info("Backup created: %s", dest_file)

    _rotate(dest_dir, keep)
    return dest_file


def _rotate(dest_dir: pathlib.Path, keep: int) -> None:
    backups = sorted(dest_dir.glob("medis-*.sqlite.gz"))
    if len(backups) > keep:
        for old in backups[:-keep]:
            old.unlink()
            logger.info("Removed old backup: %s", old.name)


def main() -> int:
    parser = argparse.ArgumentParser(description="Backup TakeYourMeds SQLite database")
    parser.add_argument("destination", nargs="?", help="Backup directory (default: ./data/backups)")
    parser.add_argument("--keep", type=int, default=DEFAULT_KEEP, help=f"Number of backups to keep (default: {DEFAULT_KEEP})")
    args = parser.parse_args()

    dest = pathlib.Path(args.destination) if args.destination else None
    try:
        backup_db(dest, keep=args.keep)
        return 0
    except Exception as exc:
        logger.error("Backup failed: %s", exc)
        return 1


if __name__ == "__main__":
    sys.exit(main())