DO $$
BEGIN
    IF NOT EXISTS (SELECT 1 FROM pg_language WHERE lanname = 'plpgsql') THEN
        CREATE LANGUAGE plpgsql;
    END IF;
END $$;

CREATE OR REPLACE FUNCTION trg_block_delivered_sales_orders_head()
RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
    IF OLD.status = 'delivered' THEN
        RAISE EXCEPTION '已交付的销售订单禁止修改或删除';
    END IF;

    IF TG_OP = 'DELETE' THEN
        RETURN OLD;
    END IF;
    RETURN NEW;
END;
$$;

DROP TRIGGER IF EXISTS block_delivered_sales_orders_head ON sales_orders;
CREATE TRIGGER block_delivered_sales_orders_head
BEFORE UPDATE OR DELETE ON sales_orders
FOR EACH ROW
EXECUTE FUNCTION trg_block_delivered_sales_orders_head();

CREATE OR REPLACE FUNCTION trg_block_delivered_sales_orders_items()
RETURNS trigger
LANGUAGE plpgsql
AS $$
DECLARE
    v_status text;
BEGIN
    SELECT status INTO v_status
    FROM sales_orders
    WHERE id = COALESCE(NEW.order_id, OLD.order_id);

    IF v_status = 'delivered' THEN
        RAISE EXCEPTION '已交付的销售订单明细禁止变更';
    END IF;

    IF TG_OP = 'DELETE' THEN
        RETURN OLD;
    END IF;
    RETURN NEW;
END;
$$;

DROP TRIGGER IF EXISTS block_delivered_sales_orders_items ON sales_order_items;
CREATE TRIGGER block_delivered_sales_orders_items
BEFORE INSERT OR UPDATE OR DELETE ON sales_order_items
FOR EACH ROW
EXECUTE FUNCTION trg_block_delivered_sales_orders_items();