"""CLI for backend migrations.

Usage:
    python -m src.lib.system.migrate inventory --to cloud                 # merge (default)
    python -m src.lib.system.migrate inventory --to cloud --mode replace  # destructive
    python -m src.lib.system.migrate vectors   --to cloud
    python -m src.lib.system.migrate vectors   --to local --mode replace

Modes:
    merge   (default, safe)  Add new rows/points; existing target rows untouched.
                             Idempotent — re-running produces the same end state.
    replace (destructive)    Wipe target completely, then copy from source.
"""

from __future__ import annotations

import argparse

from .migration import migrate_inventory, migrate_vectors


def main(argv: list[str] | None = None) -> int:
    ap = argparse.ArgumentParser(description="Migrate data between local and cloud backends")
    sub = ap.add_subparsers(dest="component", required=True)

    inv = sub.add_parser("inventory", help="Migrate the inventory DB (SQLite <-> Turso)")
    inv.add_argument("--to", required=True, choices=("local", "cloud"))
    inv.add_argument("--mode", default="merge", choices=("merge", "replace"))

    vec = sub.add_parser("vectors", help="Migrate Qdrant points (local <-> cloud)")
    vec.add_argument("--to", required=True, choices=("local", "cloud"))
    vec.add_argument("--collection", default=None, help="defaults to the active collection")
    vec.add_argument("--mode", default="merge", choices=("merge", "replace"))

    args = ap.parse_args(argv)
    direction = "local_to_cloud" if args.to == "cloud" else "cloud_to_local"

    if args.component == "inventory":
        report = migrate_inventory(direction, mode=args.mode)
        print(f"Inventory migration ({report.mode}) {direction}: "
              f"{report.total_rows} rows in {report.elapsed_ms} ms")
        for table, n in report.rows_per_table.items():
            print(f"  {table:20s} {n:>6}")
        if report.skipped_tables:
            print(f"  skipped (log tables in merge mode): {', '.join(report.skipped_tables)}")
    else:
        report = migrate_vectors(direction, collection=args.collection, mode=args.mode)
        print(f"Vector migration ({report.mode}) {direction}: "
              f"collection {report.collection!r}, "
              f"{report.points} points in {report.elapsed_ms} ms")
    return 0


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