"""
PA/POS Database Backup Script.

Creates atomic, point-in-time backups of:
  • app.db (SQLite: chats, notes, profile facts, files)
  • embeddings/embeddings.db (SQLite: vector embeddings)

Uses the SQLite Online Backup API (sqlite3.backup) to avoid database lock issues.
Retains the last N backups (default: 7) and purges older archives.
"""

from __future__ import annotations

import argparse
import logging
import shutil
import sqlite3
import tarfile
from datetime import UTC, datetime
from pathlib import Path

logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(message)s")
logger = logging.getLogger("backup")

ROOT_DIR = Path(__file__).resolve().parents[1]
BACKUPS_DIR = ROOT_DIR / "data" / "backups"
APP_DB = ROOT_DIR / "app.db"
EMBEDDINGS_DB = ROOT_DIR / "embeddings" / "embeddings.db"


def backup_sqlite(source_path: Path, dest_path: Path) -> bool:
    """Use SQLite Online Backup API for an atomic, non-blocking backup."""
    if not source_path.exists():
        logger.warning("Source database '%s' does not exist yet. Skipping.", source_path)
        return False

    dest_path.parent.mkdir(parents=True, exist_ok=True)
    try:
        src = sqlite3.connect(str(source_path))
        dst = sqlite3.connect(str(dest_path))
        with dst:
            src.backup(dst, pages=100)
        dst.close()
        src.close()
        logger.info("Successfully backed up '%s' -> '%s'", source_path.name, dest_path)
        return True
    except Exception as exc:
        logger.error("Failed to backup '%s': %s", source_path, exc)
        return False


def run_backup(retention: int = 7) -> Path:
    """Run full backup and rotate old archives."""
    BACKUPS_DIR.mkdir(parents=True, exist_ok=True)
    timestamp = datetime.now(UTC).strftime("%Y%m%d_%H%M%S")
    temp_dir = BACKUPS_DIR / f"temp_{timestamp}"
    temp_dir.mkdir(parents=True, exist_ok=True)

    backed_up_any = False
    if APP_DB.exists():
        backed_up_any |= backup_sqlite(APP_DB, temp_dir / "app.db")
    if EMBEDDINGS_DB.exists():
        backed_up_any |= backup_sqlite(EMBEDDINGS_DB, temp_dir / "embeddings.db")

    archive_path = BACKUPS_DIR / f"pabot_backup_{timestamp}.tar.gz"
    with tarfile.open(archive_path, "w:gz") as tar:
        for file in temp_dir.glob("*.db"):
            tar.add(file, arcname=file.name)

    shutil.rmtree(temp_dir, ignore_errors=True)
    logger.info("Created backup archive: %s (%d bytes)", archive_path.name, archive_path.stat().st_size)

    # Rotate old backups
    all_backups = sorted(BACKUPS_DIR.glob("pabot_backup_*.tar.gz"), key=lambda p: p.stat().st_mtime)
    if len(all_backups) > retention:
        to_delete = all_backups[:-retention]
        for old_file in to_delete:
            old_file.unlink(missing_ok=True)
            logger.info("Purged old backup: %s", old_file.name)

    return archive_path


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Backup PA/POS SQLite databases")
    parser.add_argument("--retention", type=int, default=7, help="Number of backups to keep (default: 7)")
    args = parser.parse_args()
    archive = run_backup(retention=args.retention)
    print(f"Backup complete: {archive}")