"""Helpers for bringing older local SQLite databases under Alembic control."""
import os
import sqlite3

from dotenv import load_dotenv

DEFAULT_DATABASE_URL = "sqlite+aiosqlite:///./data/discovery.db"
CURRENT_REVISION = "001"
REQUIRED_TABLES = {"discovery_conversation", "discovery_profile"}


def _sqlite_path(database_url: str) -> str | None:
    if not database_url.startswith("sqlite") or ":///" not in database_url:
        return None
    return database_url.split(":///", 1)[1]


def stamp_existing_sqlite_schema(
    database_url: str, revision: str = CURRENT_REVISION
) -> bool:
    """Stamp a pre-Alembic SQLite DB when it already has the app tables.

    Early local/dev runs could create tables through SQLAlchemy create_all()
    before Alembic was applied. In that case, `alembic upgrade head` tries to
    create tables that already exist. This marks that compatible schema as
    revision 001 so normal migrations can continue.
    """
    path = _sqlite_path(database_url)
    if not path or not os.path.exists(path):
        return False

    with sqlite3.connect(path) as conn:
        rows = conn.execute(
            "SELECT name FROM sqlite_master WHERE type = 'table'"
        ).fetchall()
        tables = {row[0] for row in rows}

        if not REQUIRED_TABLES.issubset(tables):
            return False

        if "alembic_version" in tables:
            versions = conn.execute(
                "SELECT version_num FROM alembic_version"
            ).fetchall()
            if versions:
                return False
        else:
            conn.execute(
                "CREATE TABLE alembic_version "
                "(version_num VARCHAR(32) NOT NULL)"
            )

        conn.execute(
            "INSERT INTO alembic_version (version_num) VALUES (?)",
            (revision,),
        )
        conn.commit()
        return True


def main() -> None:
    load_dotenv()
    database_url = os.getenv("DATABASE_URL", DEFAULT_DATABASE_URL)
    stamped = stamp_existing_sqlite_schema(database_url)
    if stamped:
        print(f"Stamped existing SQLite schema as Alembic revision {CURRENT_REVISION}")


if __name__ == "__main__":
    main()