import importlib
import pkgutil
from collections.abc import Iterable

import sqlalchemy as sa
from sqlalchemy.sql.selectable import ForUpdateParameter

from fansifter_common.adapters.db.base import Database


def save_instance[T](db: Database, *, instance: T, flush: bool) -> T:
    """Save instance."""
    state = sa.inspect(instance, raiseerr=True)

    if transient := state.transient:  # New instance
        db.session.add(instance)
    elif state.detached:  # Detached instance
        instance = db.session.merge(instance)
    elif state.persistent:  # Persistent instance
        pass

    # Commit or flush the instance.
    _commit_or_flush(db, flush=transient if flush is None else flush)

    return instance


def delete_instance[T](db: Database, *, instance: T, flush: bool) -> None:
    """Delete an object from the database."""
    db.session.delete(instance)
    _commit_or_flush(db, flush=flush)


def refresh_instance[T](
    db: Database,
    *,
    instance: T,
    attribute_names: Iterable[str] | None = None,
    with_for_update: ForUpdateParameter = None,
) -> None:
    """Refresh the instance from the database."""
    db.session.refresh(
        instance,
        attribute_names=attribute_names,
        with_for_update=with_for_update,
    )


# Private methods


def _commit_or_flush(db: Database, *, flush: bool) -> None:
    """Commit or flush the instance to the database."""
    if not db.in_transaction():
        db.session.commit()
    elif flush:
        db.session.flush()


def autodiscover_models(package: str, *, search: str = "models") -> None:
    """Import every ``<search>`` module and its submodules found anywhere in ``package``.

    Covers:
    - ``app.models`` / ``app.models.*``
    - ``app.artists.models`` / ``app.artists.models.*``
    """
    module = importlib.import_module(package)
    suffix = f".{search}"
    contains = f".{search}."
    for _, name, _ in pkgutil.walk_packages(module.__path__, prefix=f"{package}."):
        if name.endswith(suffix) or contains in name:
            importlib.import_module(name)