Rework trains to encourage alliances (#1697)

## Description:

This update encourages alliances by modifying how train-based trading
works. Trading is now restricted to allied networks, and allied trades
offer better rewards than self-trades, incentivizing cooperation.

Changes:
- Train destinations are now limited to stations owned by the player or
their allies.
    - Delivering a train to one’s own station grants 4,000 gold.
- Delivering a train to an ally’s station grants 5,000 gold to both the
sender and the receiver.

This system encourages players to form alliances, especially with
factory-focused players.


## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I have read and accepted the CLA agreement (only required once).

## Please put your Discord username so you can be contacted if a bug or
regression is found:

IngloriousTom

src/client/Utils.ts

@@ -5,24 +5,27 @@ export function renderTroops(troops: number): string {
   return renderNumber(troops / 10);
 }
 
-export function renderNumber(num: number | bigint): string {
+export function renderNumber(
+  num: number | bigint,
+  fixedPoints?: number,
+): string {
   num = Number(num);
   num = Math.max(num, 0);
 
   if (num >= 10_000_000) {
     const value = Math.floor(num / 100000) / 10;
-    return value.toFixed(1) + "M";
+    return value.toFixed(fixedPoints ?? 1) + "M";
   } else if (num >= 1_000_000) {
     const value = Math.floor(num / 10000) / 100;
-    return value.toFixed(2) + "M";
+    return value.toFixed(fixedPoints ?? 2) + "M";
   } else if (num >= 100000) {
     return Math.floor(num / 1000) + "K";
   } else if (num >= 10000) {
     const value = Math.floor(num / 100) / 10;
-    return value.toFixed(1) + "K";
+    return value.toFixed(fixedPoints ?? 1) + "K";
   } else if (num >= 1000) {
     const value = Math.floor(num / 10) / 100;
-    return value.toFixed(2) + "K";
+    return value.toFixed(fixedPoints ?? 2) + "K";
   } else {
     return Math.floor(num).toString();
   }

src/client/graphics/layers/FxLayer.ts

@@ -66,33 +66,27 @@ export class FxLayer implements Layer {
   }
 
   onBonusEvent(bonus: BonusEventUpdate) {
-    const tile = bonus.tile;
-    if (this.game.owner(tile) !== this.game.myPlayer()) {
+    if (this.game.player(bonus.player) !== this.game.myPlayer()) {
       // Only display text fx for the current player
       return;
     }
+    const tile = bonus.tile;
     const x = this.game.x(tile);
     let y = this.game.y(tile);
     const gold = bonus.gold;
     const troops = bonus.troops;
-    const workers = bonus.workers;
 
     if (gold > 0) {
-      const shortened = renderNumber(gold);
+      const shortened = renderNumber(gold, 0);
       this.addTextFx(`+ ${shortened}`, x, y);
       y += 10; // increase y so the next popup starts bellow
     }
 
     if (troops > 0) {
-      const shortened = renderNumber(troops);
+      const shortened = renderNumber(troops, 0);
       this.addTextFx(`+ ${shortened} troops`, x, y);
       y += 10;
     }
-
-    if (workers > 0) {
-      const shortened = renderNumber(workers);
-      this.addTextFx(`+ ${shortened} workers`, x, y);
-    }
   }
 
   addTextFx(text: string, x: number, y: number) {

src/core/configuration/DefaultConfig.ts

@@ -329,7 +329,7 @@ export class DefaultConfig implements Config {
     return Math.min(1400, Math.round(20 * Math.pow(numberOfStations, 0.5)));
   }
   trainGold(): Gold {
-    return BigInt(10_000);
+    return BigInt(4_000);
   }
   trainStationMinRange(): number {
     return 15;

src/core/execution/TrainExecution.ts

@@ -32,6 +32,10 @@ export class TrainExecution implements Execution {
     private numCars: number,
   ) {}
 
+  public owner(): Player {
+    return this.player;
+  }
+
   init(mg: Game, ticks: number): void {
     this.mg = mg;
     const stations = this.railNetwork.findStationsPath(

src/core/game/GameUpdates.ts

@@ -69,9 +69,9 @@ export type GameUpdate =
 
 export interface BonusEventUpdate {
   type: GameUpdateType.BonusEvent;
+  player: PlayerID;
   tile: TileRef;
   gold: number;
-  workers: number;
   troops: number;
 }
 

src/core/game/PlayerImpl.ts

@@ -704,9 +704,9 @@ export class PlayerImpl implements Player {
     if (tile) {
       this.mg.addUpdate({
         type: GameUpdateType.BonusEvent,
+        player: this.id(),
         tile,
         gold: Number(toAdd),
-        workers: 0,
         troops: 0,
       });
     }

src/core/game/TrainStation.ts

@@ -25,8 +25,15 @@ class CityStopHandler implements TrainStopHandler {
     trainExecution: TrainExecution,
   ): void {
     const level = BigInt(station.unit.level() + 1);
-    const goldBonus = (mg.config().trainGold() * level) / this.factor;
-    station.unit.owner().addGold(goldBonus, station.tile());
+    let goldBonus = (mg.config().trainGold() * level) / this.factor;
+    const stationOwner = station.unit.owner();
+    const trainOwner = trainExecution.owner();
+    // Share revenue with the station owner if it's not the current player
+    if (stationOwner.isFriendly(trainOwner)) {
+      goldBonus += BigInt(1_000); // Bonus for everybody when trading with an ally!
+      stationOwner.addGold(goldBonus, station.tile());
+    }
+    trainOwner.addGold(goldBonus, station.tile());
   }
 }
 
@@ -39,8 +46,15 @@ class PortStopHandler implements TrainStopHandler {
     trainExecution: TrainExecution,
   ): void {
     const level = BigInt(station.unit.level() + 1);
-    const goldBonus = (mg.config().trainGold() * level) / this.factor;
-    station.unit.owner().addGold(goldBonus, station.tile());
+    let goldBonus = (mg.config().trainGold() * level) / this.factor;
+    const stationOwner = station.unit.owner();
+    const trainOwner = trainExecution.owner();
+    // Share revenue with the station owner if it's not the current player
+    if (stationOwner.isFriendly(trainOwner)) {
+      goldBonus += BigInt(1_000); // Bonus for everybody when trading with an ally!
+      stationOwner.addGold(goldBonus, station.tile());
+    }
+    trainOwner.addGold(goldBonus, station.tile());
   }
 }
 
@@ -51,7 +65,15 @@ class FactoryStopHandler implements TrainStopHandler {
     station: TrainStation,
     trainExecution: TrainExecution,
   ): void {
-    station.unit.owner().addGold(mg.config().trainGold(), station.tile());
+    let goldBonus = mg.config().trainGold();
+    const stationOwner = station.unit.owner();
+    const trainOwner = trainExecution.owner();
+    // Share revenue with the station owner if it's not the current player
+    if (stationOwner.isFriendly(trainOwner)) {
+      goldBonus += BigInt(1_000); // Bonus for everybody when trading with an ally!
+      stationOwner.addGold(goldBonus, station.tile());
+    }
+    trainOwner.addGold(goldBonus, station.tile());
   }
 }
 
@@ -207,7 +229,10 @@ export class Cluster {
   availableForTrade(player: Player): Set<TrainStation> {
     const tradingStations = new Set<TrainStation>();
     for (const station of this.stations) {
-      if (station.tradeAvailable(player)) {
+      if (
+        station.unit.owner() === player ||
+        station.unit.owner().isFriendly(player)
+      ) {
         tradingStations.add(station);
       }
     }

tests/core/game/TrainStation.test.ts

@@ -1,5 +1,5 @@
 import { TrainExecution } from "../../../src/core/execution/TrainExecution";
-import { Game, Unit, UnitType } from "../../../src/core/game/Game";
+import { Game, Player, Unit, UnitType } from "../../../src/core/game/Game";
 import { Cluster, TrainStation } from "../../../src/core/game/TrainStation";
 
 jest.mock("../../../src/core/game/Game");
@@ -9,25 +9,28 @@ jest.mock("../../../src/core/PseudoRandom");
 describe("TrainStation", () => {
   let game: jest.Mocked<Game>;
   let unit: jest.Mocked<Unit>;
+  let player: jest.Mocked<Player>;
   let trainExecution: jest.Mocked<TrainExecution>;
 
   beforeEach(() => {
     game = {
       ticks: jest.fn().mockReturnValue(123),
       config: jest.fn().mockReturnValue({
-        trainGold: () => BigInt(10),
+        trainGold: () => BigInt(4000),
       }),
       addUpdate: jest.fn(),
       addExecution: jest.fn(),
     } as any;
 
+    player = {
+      addGold: jest.fn(),
+      id: 1,
+      canTrade: jest.fn().mockReturnValue(true),
+      isFriendly: jest.fn().mockReturnValue(false),
+    } as any;
+
     unit = {
-      owner: jest.fn().mockReturnValue({
-        addGold: jest.fn(),
-        id: 1,
-        canTrade: jest.fn().mockReturnValue(true),
-        tradingPorts: jest.fn().mockReturnValue([{ name: "Port1" }]),
-      }),
+      owner: jest.fn().mockReturnValue(player),
       level: jest.fn().mockReturnValue(1),
       tile: jest.fn().mockReturnValue({ x: 0, y: 0 }),
       type: jest.fn(),
@@ -36,6 +39,8 @@ describe("TrainStation", () => {
 
     trainExecution = {
       loadCargo: jest.fn(),
+      owner: jest.fn().mockReturnValue(player),
+      level: jest.fn(),
     } as any;
   });
 
@@ -45,7 +50,21 @@ describe("TrainStation", () => {
 
     station.onTrainStop(trainExecution);
 
-    expect(unit.owner().addGold).toHaveBeenCalledWith(10n, unit.tile());
+    expect(unit.owner().addGold).toHaveBeenCalledWith(4000n, unit.tile());
+  });
+
+  it("handles allied trade", () => {
+    unit.type.mockReturnValue(UnitType.City);
+    player.isFriendly.mockReturnValue(true);
+    const station = new TrainStation(game, unit);
+
+    station.onTrainStop(trainExecution);
+
+    expect(unit.owner().addGold).toHaveBeenCalledWith(5000n, unit.tile());
+    expect(trainExecution.owner().addGold).toHaveBeenCalledWith(
+      5000n,
+      unit.tile(),
+    );
   });
 
   it("checks trade availability (same owner)", () => {