Unfilled limit order

When the price of the pending order is within the LP price range (buy limit price <= LP price, sell limit price >= LP price), user orders of the same price will be placed in the order queue of the order book in the order of first come, first served, with different prices. Orders are sorted by price and placed in the price list. User funds are hosted in the order book contract. When the user cancels the order, the user funds will be returned to the user's account. The exchange process or other orders may trigger the order to be filled, and a certain percentage will be charged when the order is filled. The agreement fee of , after the order is filled, the user will receive another token at the pending order price