"""Backfill symbol history entries inferred from snapshot diffs.

For every commit whose files were never indexed via structured_delta, this
script diffs adjacent snapshot manifests and creates history rows with
op in (insert, replace, delete, move).

Usage:
    docker exec musehub python3 /app/deploy/backfill_history_from_snapshots.py --dry-run
    docker exec musehub python3 /app/deploy/backfill_history_from_snapshots.py
    docker exec musehub python3 /app/deploy/backfill_history_from_snapshots.py --repo-id <id>
"""
from __future__ import annotations

import argparse
import asyncio
import sys
import time

from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import sessionmaker

from musehub.db.database import get_database_url
from musehub.services.musehub_symbol_indexer import backfill_history_from_snapshots


async def run(repo_id: str | None, dry_run: bool) -> None:
    engine = create_async_engine(get_database_url(), echo=False)
    async_session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

    async with async_session() as session:
        t0 = time.monotonic()
        count = await backfill_history_from_snapshots(
            session, repo_id=repo_id, dry_run=dry_run
        )
        if not dry_run:
            await session.commit()
        elapsed = time.monotonic() - t0

    verb = "Would create" if dry_run else "Created"
    scope = f" for repo {repo_id}" if repo_id else " across all repos"
    print(f"{verb} {count} history entries{scope} in {elapsed:.1f}s")


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--dry-run", action="store_true")
    parser.add_argument("--repo-id", default=None)
    parser.add_argument("-q", "--quiet", action="store_true")
    args = parser.parse_args()

    if args.quiet:
        import logging
        logging.disable(logging.CRITICAL)

    asyncio.run(run(args.repo_id, args.dry_run))


if __name__ == "__main__":
    main()