Dan's massive refactor

Squashing 8 commits by DanAlbert:

- Track theater in ControlPoint.
Simplifies finding the owning theater of a control point. Not used yet.

- Clean some cruft out of FlightPlanBuilder.
- Clean up silly some exception handling.
- Move FlightPlan instantiation into the builder.
I'm working on moving the builder to be owned by the Flight, which will simplify callers that need to create (or recreate) flight plans for a flight.

- Simplify IBuilder constructor.
We have access to the theater via the flight's departure airbase now.

- Move FlightPlan creation into Flight.
For now this is just a callsite cleanup. Later, this will make it easier
to separate unscheduled and scheduled flights into different classes without complicating the layout/scheduling.

- Remove superfluous constructors.
- Remove unused Package field.

game/ato/package.py

@@ -6,16 +6,17 @@ from dataclasses import dataclass, field
 from datetime import timedelta
 from typing import Dict, List, Optional, TYPE_CHECKING
 
-from .flightplans.formation import FormationFlightPlan
 from game.db import Database
 from game.utils import Speed
+from .closestairfields import ObjectiveDistanceCache
 from .flight import Flight
+from .flightplans.formation import FormationFlightPlan
 from .flighttype import FlightType
 from .packagewaypoints import PackageWaypoints
 from .traveltime import TotEstimator
 
 if TYPE_CHECKING:
-    from game.theater import MissionTarget
+    from game.theater import ControlPoint, MissionTarget
 
 
 @dataclass
@@ -31,8 +32,6 @@ class Package:
     #: The set of flights in the package.
     flights: List[Flight] = field(default_factory=list)
 
-    delay: int = field(default=0)
-
     #: True if the package ToT should be reset to ASAP whenever the player makes
     #: a change. This is really a UI property rather than a game property, but
     #: we want it to persist in the save.
@@ -193,6 +192,24 @@ class Package:
             return "OCA Strike"
         return str(task)
 
+    def departure_closest_to_target(self) -> ControlPoint:
+        # We'll always have a package, but if this is being planned via the UI
+        # it could be the first flight in the package.
+        if not self.flights:
+            raise RuntimeError(
+                "Cannot determine source airfield for package with no flights"
+            )
+
+        # The package airfield is either the flight's airfield (when there is no
+        # package) or the closest airfield to the objective that is the
+        # departure airfield for some flight in the package.
+        cache = ObjectiveDistanceCache.get_closest_airfields(self.target)
+        for airfield in cache.operational_airfields:
+            for flight in self.flights:
+                if flight.departure == airfield:
+                    return airfield
+        raise RuntimeError("Could not find any airfield assigned to this package")
+
     def __hash__(self) -> int:
         # TODO: Far from perfect. Number packages?
         return hash(self.target.name)