#!/usr/bin/env python3
"""Create or restore an SQLite backup without silently overwriting a target."""

from __future__ import annotations

import argparse
import sqlite3
from contextlib import closing
from pathlib import Path


def _check_integrity(con: sqlite3.Connection) -> None:
    result = con.execute("PRAGMA integrity_check").fetchone()[0]
    if result != "ok":
        raise RuntimeError(f"SQLite integrity check failed: {result}")


def copy_database(
    source: str | Path, destination: str | Path, *, replace: bool = False
) -> None:
    source_path = Path(source).expanduser().resolve()
    destination_path = Path(destination).expanduser().resolve()
    if source_path == destination_path:
        raise ValueError("source and destination must differ")
    if not source_path.is_file():
        raise FileNotFoundError(source_path)
    if destination_path.exists() and not replace:
        raise FileExistsError(
            f"refusing to overwrite existing database: {destination_path}"
        )
    destination_path.parent.mkdir(parents=True, exist_ok=True)
    try:
        with closing(
            sqlite3.connect(f"file:{source_path}?mode=ro", uri=True)
        ) as source_con:
            _check_integrity(source_con)
            with closing(sqlite3.connect(destination_path)) as destination_con:
                source_con.backup(destination_con)
                destination_con.commit()
                _check_integrity(destination_con)
                version = destination_con.execute(
                    "SELECT MAX(version) FROM schema_migrations"
                ).fetchone()[0]
                if version is None:
                    raise RuntimeError("backup has no schema migration version")
    except sqlite3.DatabaseError as exc:
        raise RuntimeError(f"SQLite backup failed: {exc}") from exc
    print(f"backup complete: {source_path} -> {destination_path}")


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("action", choices=("backup", "restore"))
    parser.add_argument("source")
    parser.add_argument("destination")
    parser.add_argument(
        "--replace",
        action="store_true",
        help="explicitly allow replacing the destination",
    )
    args = parser.parse_args(argv)
    copy_database(args.source, args.destination, replace=args.replace)
    return 0


if __name__ == "__main__":
    raise SystemExit(main())