Add generation-time allocation for STNs.

This is a stop-gap solution so we can get a release out that supports
datalink as quickly as possible. It would be better to assign these
early so the player can select which flights should be their
team/donors, but for that we need to keep a registry in Game, plumb it
through to each Flight creation (and there are many callsites for that),
subscribe each flight to its datalink contacts (so disbanded flights do
not remain part of a network), and of course the UI itself. That'll come
later.

Follow up work:

* Filtering to only apply for the airframes that can use it
* Selection of team/donors

game/datalink/sourcetracknumber.py

@@ -0,0 +1,23 @@
+from dataclasses import dataclass
+
+from game.datalink.sourcetracknumberprefix import SourceTrackNumberPrefix
+
+
+@dataclass(frozen=True)
+class SourceTrackNumber:
+    """Source track number (STN) for a flight member."""
+
+    prefix: SourceTrackNumberPrefix
+    index: int
+
+    def __post_init__(self) -> None:
+        if self.index < 0:
+            raise ValueError("STN indexes cannot be negative")
+        if self.index >= 8:
+            raise ValueError("STN indexes must be < 8")
+
+    def __str__(self) -> str:
+        return f"{self.prefix}{self.index}"
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({self.prefix!r}, {self.index})"

game/datalink/sourcetracknumberprefix.py

@@ -0,0 +1,42 @@
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class SourceTrackNumberPrefix:
+    """The prefix of a source track number (STN) for a flight.
+
+    STNs are 5 octal digits. To make it easier for players to guess the codes for their
+    flight members, these are segmented so that the least significant digit is always
+    the flight member index. This wastes of the address space, but even at the lowest
+    density (single-member flights, ~88% waste), there are still enough prefixes for
+    4096 aircraft.
+
+    There is no per-package segmenting, however. DCS imposes a flight-size limitation on
+    us (usually four, sometimes fewer), but we do not restrict the number of flights
+    that can be in a package. If we were to carve out a digit for the package, we'd be
+    limiting the package to a max of eight flights. It's larger than a typical package,
+    but it's not unreasonable for a large OCA strike. If we carved out two digits, the
+    limit would be more than enough (64), but it would also limit the game to 64
+    packages. That's also quite high, but it's low enough that it could be hit. There's
+    some wiggle room here, since for now the only aircraft that need STNs are the F-16C,
+    F/A-18C, and A-10C II, but we shouldn't break in the unlikely case where the game is
+    composed entirely of those airframes.
+
+    Carving up the address space in different ways (such as two bits for the flight and
+    six for the package) would defeat the purpose of doing so, since they wouldn't be
+    recognizable prefixes for players, since these are expressed as octal in the jet.
+    """
+
+    value: int
+
+    def __post_init__(self) -> None:
+        if self.value < 0:
+            raise ValueError("STN prefixes cannot be negative")
+        if self.value >= 0o10000:
+            raise ValueError("STN prefixes must be < 0o10000")
+
+    def __str__(self) -> str:
+        return f"{oct(self.value)[2:]:0>4}"
+
+    def __repr__(self) -> str:
+        return f"{self.__class__.__name__}({oct(self.value)})"

game/missiongenerator/aircraft/aircraftgenerator.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import logging
+from collections.abc import Iterator
 from datetime import datetime
 from functools import cached_property
 from typing import Any, Dict, TYPE_CHECKING
@@ -16,6 +17,7 @@
 from game.ato.flighttype import FlightType
 from game.ato.package import Package
 from game.ato.starttype import StartType
+from game.datalink.sourcetracknumberprefix import SourceTrackNumberPrefix
 from game.factions.faction import Faction
 from game.missiongenerator.missiondata import MissionData
 from game.radio.radios import RadioRegistry
@@ -47,6 +49,7 @@ def __init__(
         time: datetime,
         radio_registry: RadioRegistry,
         tacan_registry: TacanRegistry,
+        stn_prefix_allocator: Iterator[int],
         unit_map: UnitMap,
         mission_data: MissionData,
         helipads: dict[ControlPoint, StaticGroup],
@@ -57,6 +60,7 @@ def __init__(
         self.time = time
         self.radio_registry = radio_registry
         self.tacan_registy = tacan_registry
+        self.stn_prefix_allocator = stn_prefix_allocator
         self.unit_map = unit_map
         # A list of per-package briefing data, which is in turn a list of per-flight
         # briefing data.
@@ -176,6 +180,7 @@ def create_and_configure_flight(
             self.time,
             self.radio_registry,
             self.tacan_registy,
+            SourceTrackNumberPrefix(next(self.stn_prefix_allocator)),
             self.mission_data,
             dynamic_runways,
             self.use_client,

game/missiongenerator/aircraft/flightdata.py

@@ -7,6 +7,7 @@
 from dcs.flyingunit import FlyingUnit
 
 from game.callsigns import create_group_callsign_from_unit
+from game.datalink.sourcetracknumber import SourceTrackNumber
 
 if TYPE_CHECKING:
     from game.ato import FlightType, FlightWaypoint, Package
@@ -66,6 +67,8 @@ class FlightData:
 
     laser_codes: list[Optional[int]]
 
+    source_track_numbers: list[SourceTrackNumber]
+
     custom_name: Optional[str]
 
     callsign: str = field(init=False)

game/missiongenerator/aircraft/flightgroupconfigurator.py

@@ -12,6 +12,8 @@
 from game.ato import Flight, FlightType
 from game.callsigns import callsign_for_support_unit
 from game.data.weapons import Pylon
+from game.datalink.sourcetracknumber import SourceTrackNumber
+from game.datalink.sourcetracknumberprefix import SourceTrackNumberPrefix
 from game.missiongenerator.logisticsgenerator import LogisticsGenerator
 from game.missiongenerator.missiondata import AwacsInfo, MissionData, TankerInfo
 from game.radio.radios import RadioFrequency, RadioRegistry
@@ -40,6 +42,7 @@ def __init__(
         time: datetime,
         radio_registry: RadioRegistry,
         tacan_registry: TacanRegistry,
+        stn_prefix: SourceTrackNumberPrefix,
         mission_data: MissionData,
         dynamic_runways: dict[str, RunwayData],
         use_client: bool,
@@ -52,6 +55,7 @@ def __init__(
         self.time = time
         self.radio_registry = radio_registry
         self.tacan_registry = tacan_registry
+        self.stn_prefix = stn_prefix
         self.mission_data = mission_data
         self.dynamic_runways = dynamic_runways
         self.use_client = use_client
@@ -66,8 +70,12 @@ def configure(self) -> FlightData:
         flight_channel = self.setup_radios()
 
         laser_codes: list[Optional[int]] = []
-        for unit, member in zip(self.group.units, self.flight.iter_members()):
+        stns = []
+        for idx, (unit, member) in enumerate(
+            zip(self.group.units, self.flight.iter_members())
+        ):
             self.configure_flight_member(unit, member, laser_codes)
+            stns.append(SourceTrackNumber(self.stn_prefix, idx))
 
         divert = None
         if self.flight.divert is not None:
@@ -134,6 +142,7 @@ def configure(self) -> FlightData:
             joker_fuel=bingo_estimator.estimate_joker(),
             custom_name=self.flight.custom_name,
             laser_codes=laser_codes,
+            source_track_numbers=stns,
         )
 
     def configure_flight_member(

game/missiongenerator/kneeboard.py

@@ -710,7 +710,9 @@ def write(self, path: Path) -> None:
 
         table = []
         for flight in self.flights:
-            for idx, laser_code in enumerate(flight.laser_codes, 1):
+            for idx, (laser_code, stn) in enumerate(
+                zip(flight.laser_codes, flight.source_track_numbers), 1
+            ):
                 # Blank the flight-wide properties to make the table easier to scan.
                 if idx > 1:
                     task = ""
@@ -725,9 +727,10 @@ def write(self, path: Path) -> None:
                         task,
                         radio,
                         "" if laser_code is None else str(laser_code),
+                        "" if stn is None else str(stn),
                     ]
                 )
-        writer.table(table, ["Aircraft", "Task", "Radio", "Laser code"])
+        writer.table(table, ["Aircraft", "Task", "Radio", "Laser code", "STN"])
 
         writer.write(path)
 

game/missiongenerator/missiongenerator.py

@@ -66,6 +66,7 @@ def __init__(self, game: Game, time: datetime) -> None:
 
         self.radio_registry = RadioRegistry()
         self.tacan_registry = TacanRegistry()
+        self.stn_prefix_allocator = iter(range(0o10000))
 
         self.generation_started = False
 
@@ -259,6 +260,7 @@ def generate_air_units(self, tgo_generator: TgoGenerator) -> None:
             self.time,
             self.radio_registry,
             self.tacan_registry,
+            self.stn_prefix_allocator,
             self.unit_map,
             mission_data=air_support_generator.mission_data,
             helipads=tgo_generator.helipads,

tests/datalink/test_sourcetracknumber.py

@@ -0,0 +1,34 @@
+import pytest
+
+from game.datalink.sourcetracknumber import SourceTrackNumber
+from game.datalink.sourcetracknumberprefix import SourceTrackNumberPrefix
+
+
+def test_limits() -> None:
+    SourceTrackNumber(SourceTrackNumberPrefix(0), 0)
+    SourceTrackNumber(SourceTrackNumberPrefix(0o7777), 7)
+    with pytest.raises(ValueError):
+        SourceTrackNumber(SourceTrackNumberPrefix(0), -1)
+    with pytest.raises(ValueError):
+        SourceTrackNumber(SourceTrackNumberPrefix(0o7777), 0o10)
+
+
+def test_str() -> None:
+    assert str(SourceTrackNumber(SourceTrackNumberPrefix(0), 0)) == "00000"
+    assert str(SourceTrackNumber(SourceTrackNumberPrefix(0o123), 4)) == "01234"
+    assert str(SourceTrackNumber(SourceTrackNumberPrefix(0o7777), 7)) == "77777"
+
+
+def test_repr() -> None:
+    assert (
+        repr(SourceTrackNumber(SourceTrackNumberPrefix(0), 0))
+        == "SourceTrackNumber(SourceTrackNumberPrefix(0o0), 0)"
+    )
+    assert (
+        repr(SourceTrackNumber(SourceTrackNumberPrefix(0o123), 4))
+        == "SourceTrackNumber(SourceTrackNumberPrefix(0o123), 4)"
+    )
+    assert (
+        repr(SourceTrackNumber(SourceTrackNumberPrefix(0o7777), 7))
+        == "SourceTrackNumber(SourceTrackNumberPrefix(0o7777), 7)"
+    )

tests/datalink/test_sourcetracknumberprefix.py

@@ -0,0 +1,24 @@
+import pytest
+
+from game.datalink.sourcetracknumberprefix import SourceTrackNumberPrefix
+
+
+def test_limits() -> None:
+    SourceTrackNumberPrefix(0)
+    SourceTrackNumberPrefix(0o7777)
+    with pytest.raises(ValueError):
+        SourceTrackNumberPrefix(0o10000)
+    with pytest.raises(ValueError):
+        SourceTrackNumberPrefix(-1)
+
+
+def test_str() -> None:
+    assert str(SourceTrackNumberPrefix(0)) == "0000"
+    assert str(SourceTrackNumberPrefix(0o123)) == "0123"
+    assert str(SourceTrackNumberPrefix(0o7777)) == "7777"
+
+
+def test_repr() -> None:
+    assert repr(SourceTrackNumberPrefix(0)) == "SourceTrackNumberPrefix(0o0)"
+    assert repr(SourceTrackNumberPrefix(0o123)) == "SourceTrackNumberPrefix(0o123)"
+    assert repr(SourceTrackNumberPrefix(0o7777)) == "SourceTrackNumberPrefix(0o7777)"