"""
MySQL 连接池管理（aiomysql）

用法：
    await init_pool()          # 应用启动时调用
    async with acquire() as conn:
        ...
    await close_pool()         # 应用关闭时调用

连接池开启 autocommit，单条语句自动提交；需要事务时显式调用 conn.begin() / conn.commit()。
"""

from contextlib import asynccontextmanager
from typing import Optional

import aiomysql

from config import MYSQL_DB, MYSQL_HOST, MYSQL_PASSWORD, MYSQL_PORT, MYSQL_USER

_pool: Optional[aiomysql.Pool] = None


async def init_pool() -> None:
    """创建全局连接池"""
    global _pool
    _pool = await aiomysql.create_pool(
        host=MYSQL_HOST,
        port=MYSQL_PORT,
        user=MYSQL_USER,
        password=MYSQL_PASSWORD,
        db=MYSQL_DB,
        charset="utf8mb4",
        autocommit=True,
        minsize=1,
        maxsize=10,
    )


async def close_pool() -> None:
    """关闭连接池"""
    global _pool
    if _pool is not None:
        _pool.close()
        await _pool.wait_closed()
        _pool = None


def get_pool() -> aiomysql.Pool:
    if _pool is None:
        raise RuntimeError("MySQL 连接池未初始化，请先调用 init_pool()")
    return _pool


@asynccontextmanager
async def acquire():
    """从连接池借出一个连接"""
    async with get_pool().acquire() as conn:
        yield conn