"""
database/core.py
SQLAlchemy 引擎与 Session 工厂。

- 同步引擎，默认连接池（QueuePool）
- 后续可替换为 create_async_engine 实现异步
"""

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

from config import settings

# -----------------------------------------------------------------------------
# 引擎配置
# -----------------------------------------------------------------------------

engine = create_engine(
    settings.DATABASE_URL,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_timeout=settings.DB_POOL_TIMEOUT,
    pool_pre_ping=settings.DB_POOL_PRE_PING,
    pool_recycle=3600,  # 1 小时回收空闲连接，避免 MySQL wait_timeout
    connect_args={
        "charset": "utf8mb4",
        "use_unicode": True,
        "init_command": "SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci",
    },
    echo=False,  # 开发时可设为 True 打印 SQL
)

# -----------------------------------------------------------------------------
# Session 工厂
# -----------------------------------------------------------------------------

SessionLocal = sessionmaker(
    bind=engine,
    autocommit=False,
    autoflush=False,
    expire_on_commit=False,  # 提交后对象仍可访问属性，便于返回响应
)