from pathlib import Path

from alembic.config import Config
from alembic.script import ScriptDirectory
from sqlalchemy import inspect, text
from sqlalchemy.engine import Connection


def expected_alembic_heads(project_root: Path | None = None) -> tuple[str, ...]:
    """Return the repository's configured Alembic heads."""

    root = project_root or Path(__file__).resolve().parents[3]
    config = Config(str(root / "alembic.ini"))
    config.set_main_option("script_location", str(root / "alembic"))
    return tuple(sorted(ScriptDirectory.from_config(config).get_heads()))


def current_alembic_revisions(connection: Connection) -> tuple[str, ...] | None:
    """Return database revisions, or ``None`` when it was never versioned."""

    if "alembic_version" not in inspect(connection).get_table_names():
        return None
    revisions = connection.execute(
        text("SELECT version_num FROM alembic_version ORDER BY version_num")
    ).scalars()
    return tuple(str(revision) for revision in revisions)