From b6895e302ebf20ba88ab9efc6cf2de40640e2bf5 Mon Sep 17 00:00:00 2001
From: Magnus Wolffelt <magnus.wolffelt@gmail.com>
Date: Sun, 1 Aug 2021 20:33:21 +0200
Subject: [PATCH] Estimate preferred patrol altitude based on max speed

(cherry picked from commit a3e3e9046f4c629114e8f46e5ef6b6718c6852c2)
---
 game/dcs/aircrafttype.py  | 28 ++++++++++++++++++++++++++++
 gen/flights/flightplan.py | 21 +++++++++++----------
 2 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/game/dcs/aircrafttype.py b/game/dcs/aircrafttype.py
index 4b588813..90c42090 100644
--- a/game/dcs/aircrafttype.py
+++ b/game/dcs/aircrafttype.py
@@ -144,6 +144,34 @@ class AircraftType(UnitType[Type[FlyingType]]):
     def max_speed(self) -> Speed:
         return kph(self.dcs_unit_type.max_speed)
 
+    @property
+    def preferred_patrol_altitude(self) -> Distance:
+        if self.patrol_altitude:
+            return self.patrol_altitude
+        else:
+            # Estimate based on max speed
+            # Aircaft with max speed 200 kph will prefer patrol at 5000 ft
+            # Aircraft with max speed 2700 kph will prefer pratrol at 33 000 ft
+            altitude_for_lowest_speed = feet(5 * 100)
+            altitude_for_highest_speed = feet(33 * 1000)
+            lowest_speed = kph(200)
+            highest_speed = kph(2700)
+            factor = (self.max_speed - lowest_speed).kph / (
+                highest_speed - lowest_speed
+            ).kph
+            altitude = (
+                altitude_for_lowest_speed
+                + (altitude_for_highest_speed - altitude_for_lowest_speed) * factor
+            )
+            logging.debug(
+                f"Preferred patrol altitude for {self.dcs_unit_type.id}: {altitude.feet}"
+            )
+            rounded_altitude = feet(round(1000 * round(altitude.feet / 1000)))
+            return max(
+                altitude_for_lowest_speed,
+                min(altitude_for_highest_speed, rounded_altitude),
+            )
+
     def alloc_flight_radio(self, radio_registry: RadioRegistry) -> RadioFrequency:
         from gen.radios import ChannelInUseError, kHz
 
diff --git a/gen/flights/flightplan.py b/gen/flights/flightplan.py
index 248846d6..2b81f911 100644
--- a/gen/flights/flightplan.py
+++ b/gen/flights/flightplan.py
@@ -1168,11 +1168,12 @@ class FlightPlanBuilder:
             raise InvalidObjectiveLocation(flight.flight_type, location)
 
         start_pos, end_pos = self.racetrack_for_objective(location, barcap=True)
-        patrol_alt = meters(
-            random.randint(
-                int(self.doctrine.min_patrol_altitude.meters),
-                int(self.doctrine.max_patrol_altitude.meters),
-            )
+
+        preferred_alt = flight.unit_type.preferred_patrol_altitude
+        randomized_alt = preferred_alt + feet(random.randint(-2, 1) * 1000)
+        patrol_alt = max(
+            self.doctrine.min_patrol_altitude,
+            min(self.doctrine.max_patrol_altitude, randomized_alt),
         )
 
         builder = WaypointBuilder(flight, self.game, self.is_player)
@@ -1406,11 +1407,11 @@ class FlightPlanBuilder:
         """
         location = self.package.target
 
-        patrol_alt = meters(
-            random.randint(
-                int(self.doctrine.min_patrol_altitude.meters),
-                int(self.doctrine.max_patrol_altitude.meters),
-            )
+        preferred_alt = flight.unit_type.preferred_patrol_altitude
+        randomized_alt = preferred_alt + feet(random.randint(-2, 1) * 1000)
+        patrol_alt = max(
+            self.doctrine.min_patrol_altitude,
+            min(self.doctrine.max_patrol_altitude, randomized_alt),
         )
 
         # Create points