current status, missing possibility to drop tomato on plate return

overcooked_simulator/counters.py

@@ -122,13 +122,37 @@ class PlateReturn(Counter):
         self.occupied_by = Plate()
 
     def pick_up(self):
-        return Plate()
+        """Gets called upon a player performing the pickup action. Gives back a plate (possibly with ingredient.
 
-    def drop_off(self, item):
-        return 0
+        Returns: A plate possibly with an ingredient on it.
 
-    def can_drop_off(self, item):
-        return False
+        """
+        give_player = self.occupied_by
+        self.occupied_by = Plate()
+        return give_player
+
+    def drop_off(self, item: HoldableItem):
+        """Takes the ingredient dropped of by the player.
+
+        Args:
+            item: The ingredient to be placed on the counter.
+        """
+        if item is Plate() and self.occupied_by is Plate():
+            self.occupied_by = None
+
+    def can_drop_off(self, item: HoldableItem):
+        """Checks whether an ingredient by the player can be dropped of.
+
+        Args:
+            item: The ingredient for which to check, if it can be placed on the counter.
+
+        Returns: True if the ingredient can be placed on the counter, False if not.
+
+        """
+        # possibility to drop off empty plate on empty plate return
+        return (
+            isinstance(self.occupied_by, Plate) and isinstance(item, Plate)
+        ) or self.occupied_by.can_combine(item)
 
     def __repr__(self):
         return "PlateReturn"

overcooked_simulator/game_items.py

@@ -18,7 +18,7 @@ class Plate(HoldableItem):
         super().__init__()
 
     def can_combine(self, other: HoldableItem):
-        return self.holds is None
+        return self.holds is None and not isinstance(other, Plate)
 
     def combine(self, other):
         self.holds = other