Convert front line units to UnitMap.

https://github.com/Khopa/dcs_liberation/issues/485

game/unitmap.py

@@ -1,16 +1,26 @@
 """Maps generated units back to their Liberation types."""
-from typing import Dict, Optional
+from dataclasses import dataclass
+from typing import Dict, Optional, Type
 
-from dcs.unitgroup import FlyingGroup
+from dcs.unitgroup import FlyingGroup, Group
+from dcs.unittype import UnitType
 
-from game.theater import Airfield
+from game import db
+from game.theater import Airfield, ControlPoint
 from gen.flights.flight import Flight
 
 
+@dataclass
+class FrontLineUnit:
+    unit_type: Type[UnitType]
+    origin: ControlPoint
+
+
 class UnitMap:
     def __init__(self) -> None:
         self.aircraft: Dict[str, Flight] = {}
         self.airfields: Dict[str, Airfield] = {}
+        self.front_line_units: Dict[str, FrontLineUnit] = {}
 
     def add_aircraft(self, group: FlyingGroup, flight: Flight) -> None:
         for unit in group.units:
@@ -31,3 +41,18 @@ class UnitMap:
 
     def airfield(self, name: str) -> Optional[Airfield]:
         return self.airfields.get(name, None)
+
+    def add_front_line_units(self, group: Group, origin: ControlPoint) -> None:
+        for unit in group.units:
+            # The actual name is a String (the pydcs translatable string), which
+            # doesn't define __eq__.
+            name = str(unit.name)
+            if name in self.front_line_units:
+                raise RuntimeError(f"Duplicate front line unit: {name}")
+            unit_type = db.unit_type_from_name(unit.type)
+            if unit_type is None:
+                raise RuntimeError(f"Unknown unit type: {unit.type}")
+            self.front_line_units[name] = FrontLineUnit(unit_type, origin)
+
+    def front_line_unit(self, name: str) -> Optional[FrontLineUnit]:
+        return self.front_line_units.get(name, None)