Improve AI air defense target prioritization.

Target the air defenses whose *threat ranges* come closest to friendly
bases rather than the closest sites themselves. In other words, the
SA-10 that is 5 miles behind the SA-6 will now be the priority.

This also treats EWRs a bit differently. If they are not protected by a
SAM their detection range will be used for determining their "threat"
range. Otherwise a heuristic is used to determine whether or not they
can be safely attacked without encroaching on the covering SAM.

game/theater/theatergroundobject.py

@@ -168,9 +168,15 @@ class TheaterGroundObject(MissionTarget):
                 max_range = max(max_range, meters(unit_range))
         return max_range
 
+    def max_detection_range(self) -> Distance:
+        return max(self.detection_range(g) for g in self.groups)
+
     def detection_range(self, group: Group) -> Distance:
         return self._max_range_of_type(group, "detection_range")
 
+    def max_threat_range(self) -> Distance:
+        return max(self.threat_range(g) for g in self.groups)
+
     def threat_range(self, group: Group, radar_only: bool = False) -> Distance:
         return self._max_range_of_type(group, "threat_range")
 

game/threatzones.py

@@ -13,7 +13,7 @@ from shapely.geometry import (
 from shapely.geometry.base import BaseGeometry
 from shapely.ops import nearest_points, unary_union
 
-from game.theater import ControlPoint
+from game.theater import ControlPoint, MissionTarget
 from game.utils import Distance, meters, nautical_miles
 from gen.flights.closestairfields import ObjectiveDistanceCache
 from gen.flights.flight import Flight, FlightWaypoint
@@ -92,6 +92,12 @@ class ThreatZones:
             LineString((self.dcs_to_shapely_point(p.position) for p in flight.points))
         )
 
+    @threatened_by_air_defense.register
+    def _threatened_by_air_defense_mission_target(self, target: MissionTarget) -> bool:
+        return self.threatened_by_air_defense(
+            self.dcs_to_shapely_point(target.position)
+        )
+
     @singledispatchmethod
     def threatened_by_radar_sam(self, target) -> bool:
         raise NotImplementedError