Move transfers one CP per turn.

https://github.com/Khopa/dcs_liberation/issues/824

game/game.py

@@ -275,7 +275,7 @@ class Game:
         for control_point in self.theater.controlpoints:
             control_point.process_turn(self)
 
-        self.transfers.complete_transfers()
+        self.transfers.perform_transfers()
 
         self.process_enemy_income()
 

game/theater/__init__.py

@@ -2,4 +2,5 @@ from .base import *
 from .conflicttheater import *
 from .controlpoint import *
 from .missiontarget import MissionTarget
+from .supplyroutes import SupplyRoute
 from .theatergroundobject import SamGroundObject

game/theater/supplyroutes.py

@@ -1,10 +1,37 @@
 from __future__ import annotations
 
-from typing import Iterator, List, Optional
+import heapq
+import math
+from collections import defaultdict
+from dataclasses import dataclass, field
+from typing import Dict, Iterator, List, Optional
 
 from game.theater.controlpoint import ControlPoint
 
 
+@dataclass(frozen=True, order=True)
+class FrontierNode:
+    cost: float
+    point: ControlPoint = field(compare=False)
+
+
+class Frontier:
+    def __init__(self) -> None:
+        self.nodes: List[FrontierNode] = []
+
+    def push(self, poly: ControlPoint, cost: float) -> None:
+        heapq.heappush(self.nodes, FrontierNode(cost, poly))
+
+    def pop(self) -> Optional[FrontierNode]:
+        try:
+            return heapq.heappop(self.nodes)
+        except IndexError:
+            return None
+
+    def __bool__(self) -> bool:
+        return bool(self.nodes)
+
+
 class SupplyRoute:
     def __init__(self, control_points: List[ControlPoint]) -> None:
         self.control_points = control_points
@@ -21,3 +48,49 @@ class SupplyRoute:
         if not connected_friendly_points:
             return None
         return SupplyRoute([control_point] + connected_friendly_points)
+
+    def shortest_path_between(
+        self, origin: ControlPoint, destination: ControlPoint
+    ) -> List[ControlPoint]:
+        if origin not in self:
+            raise ValueError(f"{origin.name} is not in this supply route")
+        if destination not in self:
+            raise ValueError(f"{destination.name} is not in this supply route")
+
+        frontier = Frontier()
+        frontier.push(origin, 0)
+
+        came_from: Dict[ControlPoint, Optional[ControlPoint]] = {origin: None}
+
+        best_known: Dict[ControlPoint, float] = defaultdict(lambda: math.inf)
+        best_known[origin] = 0.0
+
+        while (node := frontier.pop()) is not None:
+            cost = node.cost
+            current = node.point
+            if cost > best_known[current]:
+                continue
+
+            for neighbor in current.connected_points:
+                if current.captured != neighbor.captured:
+                    continue
+
+                new_cost = cost + 1
+                if new_cost < best_known[neighbor]:
+                    best_known[neighbor] = new_cost
+                    frontier.push(neighbor, new_cost)
+                    came_from[neighbor] = current
+
+        # Reconstruct and reverse the path.
+        current = destination
+        path: List[ControlPoint] = []
+        while current != origin:
+            path.append(current)
+            previous = came_from[current]
+            if previous is None:
+                raise RuntimeError(
+                    f"Could not reconstruct path to {destination} from {origin}"
+                )
+            current = previous
+        path.reverse()
+        return path

game/transfers.py

@@ -1,9 +1,10 @@
 import logging
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import Dict, List, Type
 
 from dcs.unittype import VehicleType
 from game.theater import ControlPoint
+from game.theater.supplyroutes import SupplyRoute
 
 
 @dataclass
@@ -30,6 +31,19 @@ class RoadTransferOrder(TransferOrder):
     #: The units being transferred.
     units: Dict[Type[VehicleType], int]
 
+    #: The current position of the group being transferred. Groups move one control
+    #: point a turn through the supply line.
+    position: ControlPoint = field(init=False)
+
+    def __post_init__(self) -> None:
+        self.position = self.origin
+
+    def path(self) -> List[ControlPoint]:
+        supply_route = SupplyRoute.for_control_point(self.position)
+        if supply_route is None:
+            raise RuntimeError(f"Supply route from {self.position.name} interrupted")
+        return supply_route.shortest_path_between(self.position, self.destination)
+
 
 class PendingTransfers:
     def __init__(self) -> None:
@@ -50,27 +64,66 @@ class PendingTransfers:
         self.pending_transfers.remove(transfer)
         transfer.origin.base.commision_units(transfer.units)
 
-    def complete_transfers(self) -> None:
+    def perform_transfers(self) -> None:
+        incomplete = []
         for transfer in self.pending_transfers:
-            self.complete_transfer(transfer)
+            if not self.perform_transfer(transfer):
-        self.pending_transfers.clear()
+                incomplete.append(transfer)
+        self.pending_transfers = incomplete
 
-    @staticmethod
+    def perform_transfer(self, transfer: RoadTransferOrder) -> bool:
-    def complete_transfer(transfer: RoadTransferOrder) -> None:
+        if transfer.player != transfer.destination.captured:
-        if transfer.player == transfer.destination.captured:
+            logging.info(
+                f"Transfer destination {transfer.destination.name} was captured."
+            )
+            self.handle_route_interrupted(transfer)
+            return True
+
+        supply_route = SupplyRoute.for_control_point(transfer.destination)
+        if supply_route is None or transfer.position not in supply_route:
+            logging.info(
+                f"Route from {transfer.position.name} to {transfer.destination.name} "
+                "was cut off."
+            )
+            self.handle_route_interrupted(transfer)
+            return True
+
+        path = transfer.path()
+        next_hop = path[0]
+        if next_hop == transfer.destination:
             logging.info(
                 f"Units transferred from {transfer.origin.name} to "
                 f"{transfer.destination.name}"
             )
             transfer.destination.base.commision_units(transfer.units)
-        elif transfer.player == transfer.origin.captured:
+            return True
+
         logging.info(
-                f"{transfer.destination.name} was captured. Transferring units are "
+            f"Units transferring from {transfer.origin.name} to "
-                f"returning to {transfer.origin.name}"
+            f"{transfer.destination.name} arrived at {next_hop.name}. {len(path) - 1} "
+            "turns remaining."
         )
-            transfer.origin.base.commision_units(transfer.units)
+        transfer.position = next_hop
-        else:
+        return False
+
+    @staticmethod
+    def handle_route_interrupted(transfer: RoadTransferOrder):
+        # Halt the transfer in place if safe.
+        if transfer.player == transfer.position.captured:
+            logging.info(f"Transferring units are halting at {transfer.position.name}.")
+            transfer.position.base.commision_units(transfer.units)
+            return
+
+        # If the current position was captured attempt to divert to a neighboring
+        # friendly CP.
+        for connected in transfer.position.connected_points:
+            if connected.captured == transfer.player:
+                logging.info(f"Transferring units are re-routing to {connected.name}.")
+                connected.base.commision_units(transfer.units)
+                return
+
+        # If the units are cutoff they are destroyed.
         logging.info(
-                f"Both {transfer.origin.name} and {transfer.destination.name} were "
+            f"Both {transfer.position.name} and {transfer.destination.name} were "
-                "captured. Units were surrounded and captured during transfer."
+            "captured. Units were surrounded and destroyed during transfer."
         )

qt_ui/windows/PendingTransfersDialog.py

@@ -22,6 +22,7 @@ from PySide2.QtWidgets import (
     QVBoxLayout,
 )
 
+from game.theater.supplyroutes import SupplyRoute
 from game.transfers import RoadTransferOrder
 from qt_ui.delegate_helpers import painter_context
 from qt_ui.models import GameModel, TransferModel
@@ -50,7 +51,12 @@ class TransferDelegate(QStyledItemDelegate):
 
     def second_row_text(self, index: QModelIndex) -> str:
         transfer = self.transfer(index)
-        return f"Currently at {transfer.origin}. Arrives at destination in 1 turn."
+        path = transfer.path()
+        if len(path) == 1:
+            turns = "1 turn"
+        else:
+            turns = f"{len(path)} turns"
+        return f"Currently at {transfer.position}. Arrives at destination in {turns}."
 
     def paint(
         self, painter: QPainter, option: QStyleOptionViewItem, index: QModelIndex