Refactor the sell unit changes as requested.

It works more simply now, and also doesn't immediately sell the unit.

Also adds a matching UI dialog popup for selling too many ground units.

game/event/event.py

@@ -342,6 +342,8 @@ class UnitsDeliveryEvent:
     def __init__(self, control_point: ControlPoint) -> None:
         self.to_cp = control_point
         self.units: Dict[Type[UnitType], int] = {}
+        self.bought_units = {}
+        self.sold_units = {}
 
     def __str__(self) -> str:
         return "Pending delivery to {}".format(self.to_cp)
@@ -350,6 +352,10 @@ class UnitsDeliveryEvent:
         for k, v in units.items():
             self.units[k] = self.units.get(k, 0) + v
 
+    def sell(self, units: Dict[Type[UnitType], int]) -> None:
+        for k, v in units.items():
+            self.units[k] = self.units.get(k, 0) - v
+
     def consume_each_order(self) -> Iterator[Tuple[Type[UnitType], int]]:
         while self.units:
             yield self.units.popitem()
@@ -371,7 +377,16 @@ class UnitsDeliveryEvent:
             coalition = "Ally" if self.to_cp.captured else "Enemy"
             aircraft = unit_type.id
             name = self.to_cp.name
-            game.message(
-                f"{coalition} reinforcements: {aircraft} x {count} at {name}")
-        self.to_cp.base.commision_units(self.units)
+            if count >= 0:
+                self.bought_units[unit_type] = count 
+                game.message(
+                    f"{coalition} reinforcements: {aircraft} x {count} at {name}")
+            else:
+                self.sold_units[unit_type] = 0 - count
+                game.message(
+                    f"{coalition} sold: {aircraft} x {0 - count} at {name}")
+        self.to_cp.base.commision_units(self.bought_units)
+        self.to_cp.base.commit_losses(self.sold_units)
         self.units = {}
+        self.bought_units = {}
+        self.sold_units = {}

game/inventory.py

@@ -98,7 +98,6 @@ class GlobalAircraftInventory:
         inventory = self.inventories[control_point]
         for aircraft, count in control_point.base.aircraft.items():
             inventory.add_aircraft(aircraft, count)
-            control_point.base.sold_units[aircraft] = 0
 
     def for_control_point(
             self,

game/theater/base.py

@@ -29,7 +29,6 @@ class Base:
         self.aa: Dict[AirDefence, int] = {}
         self.commision_points: Dict[Type, float] = {}
         self.strength = 1
-        self.sold_units = {}
 
     @property
     def total_aircraft(self) -> int: