from __future__ import annotations
from flask import Flask
from sqlalchemy.orm import scoped_session
from ..engines import CRUDKitRuntime
from ..config import Config

def init_app(app: Flask, *, runtime: CRUDKitRuntime | None = None, config: type[Config] | None == None):
    """
    Initializes CRUDKit for a Flask app. Provies `app.extensions['crudkit']`
    with a runtime (engine + session_factory). Caller manages session lifecycle.
    """
    runtime = runtime or CRUDKitRuntime(config=config)
    app.extensions.setdefault("crudkit", {})
    app.extensions["crudkit"]["runtime"] = runtime

    Session = runtime.session_factory
    if Session is not None:
        app.extensions["crudkit"]["Session"] = scoped_session(Session)

    return runtime