from __future__ import annotations

import os

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.pool import NullPool

_ENGINE: Engine | None = None
_SESSION_FACTORY: sessionmaker | None = None


def database_url() -> str:
    return os.getenv("DATABASE_URL", "postgresql+psycopg://agent:agent@db:5432/agent")


def get_engine() -> Engine:
    global _ENGINE
    if _ENGINE is None:
        _ENGINE = create_engine(database_url(), poolclass=NullPool, future=True)
    return _ENGINE


def get_session_factory() -> sessionmaker:
    global _SESSION_FACTORY
    if _SESSION_FACTORY is None:
        _SESSION_FACTORY = sessionmaker(bind=get_engine(), autoflush=False, autocommit=False)
    return _SESSION_FACTORY