Add CycleShopCategory

game/scripts/utility/actions.rpy

@@ -1,5 +1,5 @@
 init python:
-    class SwitchShopCategory(Action):
+    class SetShopCategory(Action):
         def __init__(self, category: str, items: list):
             self.category = category
             self.items = items
@@ -19,6 +19,37 @@ init python:
 
             renpy.restart_interaction()
 
+    class CycleShopCategory(Action):
+        def __init__(self, screenvar: str, items: dict, reverse=False):
+            self.screenvar = screenvar
+            self.items = items
+            self.reverse = reverse
+
+        def __call__(self):
+            cs = renpy.current_screen()
+
+            if cs is None:
+                raise Exception("No current screen.")
+
+            scope = cs.scope
+            var = self.screenvar
+            current = scope[var]
+
+            keys_list = list(self.items.keys())
+
+            try:
+                current_index = keys_list.index(current)
+            except ValueError:
+                current_index = -1
+
+            step = -1 if self.reverse else 1
+            next_index = (current_index + step) % len(keys_list)
+            next_key = keys_list[next_index]
+
+            scope[var] = next_key
+
+            SetShopCategory(next_key, self.items[next_key])()
+
     class SortFilter(Action):
         def __init__(self, screenvar: str, sort_keys=None, filter_keys=None):
             self.screenvar = screenvar