from __future__ import annotations

import os
from functools import lru_cache

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine


@lru_cache(maxsize=1)
def get_engine() -> Engine:
    """Return a cached SQLAlchemy engine configured from DATABASE_URL."""
    database_url = os.getenv(
        "DATABASE_URL",
        "mysql+pymysql://root:12345678@localhost:3306/data-ge?charset=utf8mb4",
    )
    connect_args = {}
    if database_url.startswith("sqlite"):
        connect_args["check_same_thread"] = False

    return create_engine(
        database_url,
        pool_pre_ping=True,
        future=True,
        connect_args=connect_args,
    )