"""asyncpg 连接池管理 —— engine 模块对 TimescaleDB 的唯一切入点。"""

import asyncpg
from engine.config.settings import DB_DSN, db as db_config

_pool: asyncpg.Pool | None = None


async def get_pool() -> asyncpg.Pool:
    """获取或创建 asyncpg 连接池（懒初始化，复用）。"""
    global _pool
    if _pool is None:
        _pool = await asyncpg.create_pool(
            dsn=DB_DSN,
            min_size=2,
            max_size=10,
            command_timeout=30,
            server_settings={"default_transaction_read_only": "on"},
        )
    return _pool


async def close_pool() -> None:
    """关闭连接池（应用退出时调用）"""
    global _pool
    if _pool:
        await _pool.close()
        _pool = None