chore: optional size or price on order update

Author: fasenderos

src/order.ts

@@ -11,9 +11,9 @@ interface IOrder {
 }
 
 export interface OrderUpdate {
-  size: number
-  price: number
   side: Side
+  size?: number
+  price?: number
 }
 
 export enum OrderType {

src/orderside.ts

@@ -107,9 +107,10 @@ export class OrderSide {
       // Quantity changed. Price is the same.
       const oldOrderSize: number = oldOrder.size.toNumber()
       const strPrice = oldOrder.price.toString()
+      const newOrderPrize: number = orderUpdate.price ?? oldOrder.price
       this._volume = this._volume.plus(orderUpdate.size - oldOrderSize)
       this._total = this._total.plus(
-        orderUpdate.size * orderUpdate.price - oldOrderSize * oldOrder.price
+        orderUpdate.size * newOrderPrize - oldOrderSize * oldOrder.price
       )
       this._prices[strPrice].updateOrderSize(oldOrder, orderUpdate.size)
       return oldOrder