from sqlalchemy import create_engine, event
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

from app.core.config import settings

engine = create_engine(
    settings.DATABASE_URL,
    pool_pre_ping=True,
    pool_recycle=settings.DB_POOL_RECYCLE_SEC,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_reset_on_return="rollback",
    connect_args={
        "connect_timeout": settings.DB_CONNECT_TIMEOUT_SEC,
        "read_timeout": settings.DB_READ_TIMEOUT_SEC,
        "write_timeout": settings.DB_WRITE_TIMEOUT_SEC,
    },
    echo=settings.DEBUG,
)

# 避免 commit 后 ORM 实例自动过期，导致读取字段时回表 SELECT（高频接口会显著拖慢）
SessionLocal = sessionmaker(autocommit=False, autoflush=False, expire_on_commit=False, bind=engine)

Base = declarative_base()


def get_db():
    """获取数据库会话"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


@event.listens_for(Base, "before_insert", propagate=True)
def _auto_fill_create_dept_id(mapper, connection, target):
    """ORM before_insert 钩子：当 create_dept_id 为空时，自动从请求上下文填充当前用户部门 ID"""
    if hasattr(target, "create_dept_id") and not getattr(target, "create_dept_id", None):
        from app.core.context import current_user_dept_id
        dept_id = current_user_dept_id.get("")
        if dept_id:
            target.create_dept_id = dept_id