Interface ShopLayoutHandler

The logic behind the look-and-feel of a ShopLayout.
It receives an ShopLayoutHandler.OpenEvent that contains various informations that are needed in that event to display it.
The event build(OpenEvent), that gets called whenever it's time to process it, gets called very frequently, including whenever the player changes his page. You should try to make your code as efficient as possible. At the end you're gonna return a GUI, probably of the type ChestGUI, that will be displayed to the player. Use methods that are included in your ShopLayoutHandler.OpenEvent, such as ShopLayoutHandler.OpenEvent.build(ShopPage) to construct clickable buttons for the GUI that handle the item purchasing, page changing and etc.