Factory spawns trains (#1408)

## Description:

- Change trains so it spawns from factories only
- Increase train frequency as they will now spawn from a single
structure.
- Factory will spawn more trains depending on its level
- Fix port to connect to nearby railroads
- Add factory description

## 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 understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

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

IngloriousTom

---------

Co-authored-by: Tom Rouillard <trouilla@mathworks.com>
Co-authored-by: evanpelle <evanpelle@gmail.com>

resources/lang/en.json

@@ -90,6 +90,8 @@
     "build_desc": "Description",
     "build_city": "City",
     "build_city_desc": "Increases your max population. Useful when you can't expand your territory or you're about to hit your population limit.",
+    "build_factory": "Factory",
+    "build_factory_desc": "Creates railroads automatically with nearby structures, and spawns trains sporadically.",
     "build_defense": "Defense Post",
     "build_defense_desc": "Increases defenses around nearby borders, which show a checkered pattern. Attacks from enemies are slower and have more casualties.",
     "build_port": "Port",
@@ -409,8 +411,9 @@
       "sam_launcher": "Defends against incoming nukes",
       "warship": "Captures trade ships, destroys ships and boats",
       "port": "Sends trade ships to generate gold",
-      "defense_post": "Increase defenses of nearby borders",
-      "city": "Increase max population"
+      "defense_post": "Increases defenses of nearby borders",
+      "city": "Increases max population",
+      "factory": "Creates railroads and spawns trains"
     },
     "not_enough_money": "Not enough money"
   },

src/client/styles.css

@@ -369,6 +369,11 @@ label.option-card:hover {
   mask: url("../../resources/images/CityIconWhite.svg") no-repeat center / cover;
 }
 
+#helpModal .factory-icon {
+  mask: url("../../resources/images/FactoryIconWhite.svg") no-repeat center /
+    cover;
+}
+
 #helpModal .defense-post-icon {
   mask: url("../../resources/images/ShieldIconWhite.svg") no-repeat center /
     cover;

src/core/configuration/DefaultConfig.ts

@@ -326,7 +326,7 @@ export class DefaultConfig implements Config {
     return this._gameConfig.infiniteTroops;
   }
   trainSpawnRate(numberOfStations: number): number {
-    return Math.min(1400, Math.round(70 * Math.pow(numberOfStations, 0.8)));
+    return Math.min(1400, Math.round(20 * Math.pow(numberOfStations, 0.5)));
   }
   trainGold(): Gold {
     return BigInt(10_000);

src/core/execution/FactoryExecution.ts

@@ -51,11 +51,11 @@ export class FactoryExecution implements Execution {
         this.game.config().trainStationMaxRange(),
         [UnitType.City, UnitType.Port, UnitType.Factory],
       );
-      // Use different seeds or trains will spawn simultaneously
-      let seed = 0;
+
+      this.game.addExecution(new TrainStationExecution(this.factory, true));
       for (const { unit } of structures) {
         if (!unit.hasTrainStation()) {
-          this.game.addExecution(new TrainStationExecution(unit, ++seed));
+          this.game.addExecution(new TrainStationExecution(unit));
         }
       }
     }

src/core/execution/PortExecution.ts

@@ -2,6 +2,7 @@ import { Execution, Game, Player, Unit, UnitType } from "../game/Game";
 import { TileRef } from "../game/GameMap";
 import { PseudoRandom } from "../PseudoRandom";
 import { TradeShipExecution } from "./TradeShipExecution";
+import { TrainStationExecution } from "./TrainStationExecution";
 
 export class PortExecution implements Execution {
   private active = true;
@@ -36,6 +37,7 @@ export class PortExecution implements Execution {
         return;
       }
       this.port = this.player.buildUnit(UnitType.Port, spawn, {});
+      this.createStation();
     }
 
     if (!this.port.isActive()) {
@@ -84,4 +86,18 @@ export class PortExecution implements Execution {
     }
     return false;
   }
+
+  createStation(): void {
+    if (this.port !== null) {
+      const nearbyFactory = this.mg.hasUnitNearby(
+        this.port.tile()!,
+        this.mg.config().trainStationMaxRange(),
+        UnitType.Factory,
+        this.player.id(),
+      );
+      if (nearbyFactory) {
+        this.mg.addExecution(new TrainStationExecution(this.port));
+      }
+    }
+  }
 }

src/core/execution/TrainStationExecution.ts

@@ -6,13 +6,17 @@ import { TrainExecution } from "./TrainExecution";
 export class TrainStationExecution implements Execution {
   private mg: Game;
   private active: boolean = true;
-  private random: PseudoRandom | null = null;
+  private random: PseudoRandom;
   private station: TrainStation | null = null;
   private numCars: number = 5;
+  private lastSpawnTick: number = 0;
+  private ticksCooldown: number = 10; // Minimum cooldown between two trains
   constructor(
     private unit: Unit,
-    private randomSeed?: number,
-  ) {}
+    private spawnTrains?: boolean, // If set, the station will spawn trains
+  ) {
+    this.unit.setTrainStation(true);
+  }
 
   isActive(): boolean {
     return this.active;
@@ -20,8 +24,9 @@ export class TrainStationExecution implements Execution {
 
   init(mg: Game, ticks: number): void {
     this.mg = mg;
-    this.random = new PseudoRandom(mg.ticks() + (this.randomSeed ?? 0));
-    this.unit.setTrainStation(true);
+    if (this.spawnTrains) {
+      this.random = new PseudoRandom(mg.ticks());
+    }
   }
 
   tick(ticks: number): void {
@@ -36,36 +41,57 @@ export class TrainStationExecution implements Execution {
       this.station = new TrainStation(this.mg, this.unit);
       this.mg.railNetwork().connectStation(this.station);
     }
-    if (!this.station.isActive() || !this.random) {
+    if (!this.station.isActive()) {
       this.active = false;
       return;
     }
-    const cluster = this.station.getCluster();
+    this.spawnTrain(this.station, ticks);
+  }
+
+  private shouldSpawnTrain(clusterSize: number): boolean {
+    const spawnRate = this.mg.config().trainSpawnRate(clusterSize);
+    for (let i = 0; i < this.unit!.level(); i++) {
+      if (this.random.chance(spawnRate)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  private spawnTrain(station: TrainStation, currentTick: number) {
+    if (
+      !this.spawnTrains ||
+      currentTick - this.lastSpawnTick < this.ticksCooldown
+    ) {
+      return;
+    }
+    const cluster = station.getCluster();
     if (cluster === null) {
       return;
     }
     const availableForTrade = cluster.availableForTrade(this.unit.owner());
-    if (
-      availableForTrade.size === 0 ||
-      !this.random.chance(
-        this.mg.config().trainSpawnRate(availableForTrade.size),
-      )
-    ) {
+    if (availableForTrade.size === 0) {
       return;
     }
+    if (!this.shouldSpawnTrain(availableForTrade.size)) {
+      return;
+    }
+
     // Pick a destination randomly.
     // Could be improved to pick a lucrative trip
-    const destination = this.random.randFromSet(availableForTrade);
-    if (destination !== this.station) {
+    const destination: TrainStation =
+      this.random.randFromSet(availableForTrade);
+    if (destination !== station) {
       this.mg.addExecution(
         new TrainExecution(
           this.mg.railNetwork(),
           this.unit.owner(),
-          this.station,
+          station,
           destination,
           this.numCars,
         ),
       );
+      this.lastSpawnTick = currentTick;
     }
   }
 

src/core/game/TrainStation.ts

@@ -45,20 +45,13 @@ class PortStopHandler implements TrainStopHandler {
 }
 
 class FactoryStopHandler implements TrainStopHandler {
+  private factor: bigint = BigInt(2);
   onStop(
     mg: Game,
     station: TrainStation,
     trainExecution: TrainExecution,
   ): void {
-    const goldBonus = mg.config().trainGold();
-    station.unit.owner().addGold(goldBonus);
-    mg.addUpdate({
-      type: GameUpdateType.BonusEvent,
-      tile: station.tile(),
-      gold: Number(goldBonus),
-      workers: 0,
-      troops: 0,
-    });
+    station.unit.owner().addGold(mg.config().trainGold(), station.tile());
   }
 }