"""
db_sync.py — Persists the Label Studio SQLite DB across HF Space rebuilds
by syncing to/from the private TrustLLMeu/saga-db-backup dataset repo.

Usage:
  python3 db_sync.py restore   # pull DB from HF repo → /data/ls/
  python3 db_sync.py backup    # push /data/ls/label_studio.sqlite3 → HF repo
  python3 db_sync.py watch     # backup every INTERVAL seconds (run in background)
"""

import os
import shutil
import sqlite3
import sys
import tempfile
import time

HF_TOKEN   = os.environ.get("HF_TOKEN", "")
BACKUP_REPO = "TrustLLMeu/saga-db-backup"
REMOTE_FILE = "label_studio.sqlite3"
INTERVAL   = 300   # backup every 5 minutes

# Find the real LS DB — the one with the most users.
# LS may store its DB at /data/label_studio.sqlite3 (not /data/ls/label_studio.sqlite3).
def _find_db_path():
    import glob as _g
    candidates = (
        _g.glob("/data/**/*.sqlite3", recursive=True) +
        _g.glob("/label-studio/**/*.sqlite3", recursive=True)
    )
    best, best_n = "/data/ls/label_studio.sqlite3", -1
    for p in candidates:
        try:
            c = sqlite3.connect(p)
            n = c.execute("SELECT COUNT(*) FROM htx_user").fetchone()[0]
            c.close()
            if n > best_n:
                best, best_n = p, n
        except Exception:
            pass
    print(f"[db_sync] DB path: {best} ({best_n} users)", flush=True)
    return best

DB_PATH = _find_db_path()


def _api():
    from huggingface_hub import HfApi
    if not HF_TOKEN:
        raise RuntimeError("HF_TOKEN env var not set")
    return HfApi(token=HF_TOKEN)


def _safe_copy(src, dst):
    """Copy a SQLite DB using the backup API so WAL data is included."""
    with sqlite3.connect(src) as src_conn:
        with sqlite3.connect(dst) as dst_conn:
            src_conn.backup(dst_conn)


def restore():
    """Download DB from HF backup repo if it exists. Returns True if restored."""
    try:
        api = _api()
        # Check if backup file exists in repo
        files = api.list_repo_files(BACKUP_REPO, repo_type="dataset")
        if REMOTE_FILE not in list(files):
            print(f"[db_sync] No backup found in {BACKUP_REPO} — fresh start.", flush=True)
            return False

        print(f"[db_sync] Restoring DB from {BACKUP_REPO}...", flush=True)
        os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)

        # Download to a temp file first, then atomically replace
        tmp = DB_PATH + ".restore_tmp"
        path = api.hf_hub_download(
            repo_id=BACKUP_REPO,
            filename=REMOTE_FILE,
            repo_type="dataset",
            local_dir=os.path.dirname(tmp),
            local_dir_use_symlinks=False,
        )
        shutil.move(path, DB_PATH)
        size = os.path.getsize(DB_PATH)
        print(f"[db_sync] Restored DB ({size:,} bytes).", flush=True)
        return True
    except Exception as e:
        print(f"[db_sync] Restore failed: {e}", flush=True)
        return False


def backup():
    """Upload current DB to HF backup repo using SQLite backup API (handles WAL)."""
    if not os.path.exists(DB_PATH):
        print(f"[db_sync] No DB at {DB_PATH} — skipping backup.", flush=True)
        return False
    tmp = None
    try:
        api = _api()
        # Use SQLite backup API to create a consistent snapshot that includes WAL data.
        # Uploading the raw .sqlite3 file misses uncommitted WAL transactions.
        tmp = DB_PATH + ".upload_tmp"
        _safe_copy(DB_PATH, tmp)
        size = os.path.getsize(tmp)
        # Verify the copy has data
        with sqlite3.connect(tmp) as check:
            n = check.execute("SELECT COUNT(*) FROM htx_user").fetchone()[0]
        print(f"[db_sync] Backing up DB ({size:,} bytes, {n} users) → {BACKUP_REPO}...", flush=True)
        api.upload_file(
            path_or_fileobj=tmp,
            path_in_repo=REMOTE_FILE,
            repo_id=BACKUP_REPO,
            repo_type="dataset",
            commit_message=f"Auto-backup from HF Space ({n} users)",
        )
        print(f"[db_sync] Backup complete ({n} users).", flush=True)
        return True
    except Exception as e:
        print(f"[db_sync] Backup failed: {e}", flush=True)
        return False
    finally:
        if tmp and os.path.exists(tmp):
            try:
                os.unlink(tmp)
            except Exception:
                pass


def watch():
    """Run backup every INTERVAL seconds."""
    print(f"[db_sync] Watch mode: backing up every {INTERVAL}s.", flush=True)
    while True:
        time.sleep(INTERVAL)
        backup()


if __name__ == "__main__":
    cmd = sys.argv[1] if len(sys.argv) > 1 else "backup"
    if cmd == "restore":
        ok = restore()
        sys.exit(0 if ok else 1)
    elif cmd == "backup":
        ok = backup()
        sys.exit(0 if ok else 1)
    elif cmd == "watch":
        watch()
    else:
        print(f"Usage: db_sync.py restore|backup|watch", flush=True)
        sys.exit(1)