"""Apply Alembic migrations programmatically at startup — no separate step in the container.

`python -m app.db.migrate [revision]` upgrades the DB from DATABASE_URL (default: head).
"""

import asyncio
import sys

from alembic import command
from alembic.config import Config
from sqlalchemy.engine import Connection
from sqlalchemy.ext.asyncio import AsyncEngine

from app.config import DatabaseSettings
from app.db.session import make_engine

SCRIPT_LOCATION = "app.db:migrations"


def alembic_config(connection: Connection | None = None) -> Config:
    cfg = Config()
    cfg.set_main_option("script_location", SCRIPT_LOCATION)
    # env.py reuses this connection instead of opening its own (async engine, one transaction)
    cfg.attributes["connection"] = connection
    return cfg


async def upgrade(engine: AsyncEngine, revision: str = "head") -> None:
    async with engine.begin() as conn:
        await conn.run_sync(lambda sync_conn: command.upgrade(alembic_config(sync_conn), revision))


async def downgrade(engine: AsyncEngine, revision: str) -> None:
    async with engine.begin() as conn:
        await conn.run_sync(lambda sync_conn: command.downgrade(alembic_config(sync_conn), revision))


def main() -> None:
    revision = sys.argv[1] if len(sys.argv) > 1 else "head"

    async def _run() -> None:
        engine = make_engine(DatabaseSettings().url)
        try:
            await upgrade(engine, revision)
        finally:
            await engine.dispose()

    asyncio.run(_run())


if __name__ == "__main__":
    main()