"""Database helpers shared across the backend."""

from __future__ import annotations

import asyncio
import datetime
from typing import Any, Callable, Dict, List, Optional, Union

from sqlalchemy import create_engine, text
from sqlalchemy.orm import Session, declarative_base, sessionmaker

from . import config

Base = declarative_base()
ENGINE = None
SessionLocal: Optional[sessionmaker] = None
FILE_LOCK = asyncio.Lock()

MessageContent = Union[str, List[Dict[str, Any]]]


def now_utc() -> datetime.datetime:
    return datetime.datetime.utcnow()


def ensure_directories() -> None:
    for path in [config.DATA_DIR, config.BACKUP_DIR, config.BLOG_DIR, config.UPLOAD_DIR, config.STATIC_DIR]:
        path.mkdir(parents=True, exist_ok=True)


def ensure_database_initialized() -> None:
    global ENGINE, SessionLocal
    if ENGINE is not None:
        return

    raw_engine = create_engine(config.RAW_DATABASE_URL, future=True, pool_pre_ping=True)
    with raw_engine.connect() as connection:
        connection.execute(
            text(
                f"CREATE DATABASE IF NOT EXISTS `{config.DATABASE_NAME}` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci"
            )
        )
    raw_engine.dispose()

    ENGINE = create_engine(config.DATABASE_URL, future=True, pool_pre_ping=True)
    SessionLocal = sessionmaker(bind=ENGINE, autoflush=False, expire_on_commit=False, future=True)
    Base.metadata.create_all(bind=ENGINE)


async def db_call(func: Callable[[Session], Any], *args: Any, **kwargs: Any) -> Any:
    def wrapped() -> Any:
        if SessionLocal is None:
            raise RuntimeError("数据库尚未初始化")
        with SessionLocal() as session:
            return func(session, *args, **kwargs)

    return await asyncio.to_thread(wrapped)