WebGL: return of factory/defence post radii, and railroad highlighting when placing city/port right on top

src/client/UIState.ts

@@ -1,10 +1,7 @@
 import { PlayerBuildableUnitType } from "../core/game/Game";
-import { TileRef } from "../core/game/GameMap";
 
 export interface UIState {
   attackRatio: number;
   ghostStructure: PlayerBuildableUnitType | null;
-  overlappingRailroads: number[];
-  ghostRailPaths: TileRef[][];
   rocketDirectionUp: boolean;
 }

src/client/controllers/BuildPreviewController.ts

@@ -191,15 +191,6 @@ export class BuildPreviewController implements Controller {
 
         this.ghostUnit.buildableUnit = unit;
 
-        if (unit.canUpgrade || unit.canBuild === false) {
-          // No rail-snap overlap for upgrades or invalid placements.
-          this.uiState.overlappingRailroads = [];
-          this.uiState.ghostRailPaths = [];
-        } else {
-          this.uiState.overlappingRailroads = unit.overlappingRailroads;
-          this.uiState.ghostRailPaths = unit.ghostRailPaths;
-        }
-
         if (this.pendingConfirm !== null) {
           const ev = this.pendingConfirm;
           this.pendingConfirm = null;
@@ -326,14 +317,22 @@ export class BuildPreviewController implements Controller {
     // Range circle: SAM placement preview shows targetable radius; nuke
     // previews show the outer blast radius at the target tile.
     let rangeRadius = 0;
-    if (u.type === UnitType.SAMLauncher) {
-      const level = this.resolveGhostRangeLevel(u) ?? 1;
-      rangeRadius = this.game.config().samRange(level);
-    } else if (
-      u.type === UnitType.AtomBomb ||
-      u.type === UnitType.HydrogenBomb
-    ) {
-      rangeRadius = this.game.config().nukeMagnitudes(u.type).outer;
+    switch (u.type) {
+      case UnitType.SAMLauncher: {
+        const level = this.resolveGhostRangeLevel(u) ?? 1;
+        rangeRadius = this.game.config().samRange(level);
+        break;
+      }
+      case UnitType.AtomBomb:
+      case UnitType.HydrogenBomb:
+        rangeRadius = this.game.config().nukeMagnitudes(u.type).outer;
+        break;
+      case UnitType.Factory:
+        rangeRadius = this.game.config().trainStationMaxRange();
+        break;
+      case UnitType.DefensePost:
+        rangeRadius = this.game.config().defensePostRange();
+        break;
     }
 
     return {
@@ -428,7 +427,6 @@ export class BuildPreviewController implements Controller {
   private clearGhostStructure() {
     this.pendingConfirm = null;
     this.ghostUnit = null;
-    this.uiState.ghostRailPaths = [];
     this.lastGhostData = null;
     this.view.updateGhostPreview(null);
     this.view.updateNukeTrajectory(null);

src/client/hud/GameRenderer.ts

@@ -51,8 +51,6 @@ export function createRenderer(
   const uiState: UIState = {
     attackRatio: 20,
     ghostStructure: null,
-    overlappingRailroads: [],
-    ghostRailPaths: [],
     rocketDirectionUp: true,
   };
 

src/client/render/types/Renderer.ts

@@ -1,3 +1,5 @@
+import type { TileRef } from "../../../core/game/GameMap";
+
 /** TrainType enum — numeric values matching UnitState.trainType. */
 export enum TrainType {
   Engine = 0,
@@ -152,8 +154,8 @@ export interface GhostPreviewData {
   canBuild: boolean; // Valid placement?
   canUpgrade: boolean; // Upgrading existing structure?
   cost: number; // Gold cost
-  ghostRailPaths: number[][]; // TileRef paths (City/Port only)
-  overlappingRailroads: number[]; // Rail IDs in snap zone
+  ghostRailPaths: TileRef[][]; // TileRef paths (City/Port only)
+  overlappingRailroads: TileRef[]; // TileRefs containing rails in snap zone
   ownerID: number; // Player's smallID (for color)
   /** Tile position of existing structure being upgraded (null if fresh build). */
   upgradeTargetTile: number | null;

src/core/game/Game.ts

@@ -985,7 +985,7 @@ export interface BuildableUnit {
   canUpgrade: number | false;
   type: PlayerBuildableUnitType;
   cost: Gold;
-  overlappingRailroads: number[];
+  overlappingRailroads: TileRef[];
   ghostRailPaths: TileRef[][];
 }
 

src/core/game/RailNetwork.ts

@@ -8,7 +8,7 @@ export interface RailNetwork {
   removeStation(unit: Unit): void;
   findStationsPath(from: TrainStation, to: TrainStation): TrainStation[];
   stationManager(): StationManager;
-  overlappingRailroads(tile: TileRef): number[];
+  overlappingRailroads(tile: TileRef): TileRef[];
   computeGhostRailPaths(unitType: UnitType, tile: TileRef): TileRef[][];
   recomputeClusters(): void;
 }

src/core/game/RailNetworkImpl.ts

@@ -223,10 +223,14 @@ export class RailNetworkImpl implements RailNetwork {
     return editedClusters.size !== 0;
   }
 
-  overlappingRailroads(tile: TileRef): number[] {
-    return [...this.railGrid.query(tile, this.stationRadius)].map(
-      (railroad: Railroad) => railroad.id,
-    );
+  overlappingRailroads(tile: TileRef): TileRef[] {
+    const tiles = new Set<TileRef>();
+    for (const railroad of this.railGrid.query(tile, this.stationRadius)) {
+      for (const t of railroad.tiles) {
+        tiles.add(t);
+      }
+    }
+    return Array.from(tiles).sort((a, b) => a - b);
   }
 
   private canSnapToExistingRailway(tile: TileRef): boolean {

tests/InputHandler.test.ts

@@ -65,8 +65,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       },
       mockCanvas,
       eventBus,
@@ -541,8 +539,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -597,8 +593,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -649,8 +643,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -671,8 +663,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -699,8 +689,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -724,8 +712,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
       inputHandler = new InputHandler(
         mockGameView,
@@ -752,8 +738,6 @@ describe("InputHandler AutoUpgrade", () => {
         attackRatio: 20,
         ghostStructure: null,
         rocketDirectionUp: true,
-        overlappingRailroads: [],
-        ghostRailPaths: [],
       } as UIState;
     });
 
@@ -892,8 +876,6 @@ describe("Warship box selection (Shift+drag)", () => {
       attackRatio: 20,
       ghostStructure: null,
       rocketDirectionUp: true,
-      overlappingRailroads: [],
-      ghostRailPaths: [],
     } as UIState;
     inputHandler = new InputHandler(
       mockGameView,

tests/core/game/RailNetwork.test.ts

@@ -168,6 +168,33 @@ describe("RailNetworkImpl", () => {
     expect(neighborStation.setCluster).toHaveBeenCalled();
   });
 
+  describe("overlappingRailroads", () => {
+    test("returns deterministic deduplicated TileRef array", () => {
+      const tile = 42 as any;
+      const railGridMock = {
+        query: vi.fn(
+          () => new Set([{ tiles: [50, 42, 60] }, { tiles: [60, 45, 42] }]),
+        ),
+      };
+      (network as any).railGrid = railGridMock;
+
+      const result = network.overlappingRailroads(tile);
+
+      expect(railGridMock.query).toHaveBeenCalledWith(tile, 3);
+      expect(result).toEqual([42, 45, 50, 60]); // Deduplicated and sorted
+    });
+
+    test("returns empty array when no railroads overlap", () => {
+      const tile = 42 as any;
+      const railGridMock = { query: vi.fn(() => new Set()) };
+      (network as any).railGrid = railGridMock;
+
+      const result = network.overlappingRailroads(tile);
+
+      expect(result).toEqual([]);
+    });
+  });
+
   describe("computeGhostRailPaths", () => {
     test("returns empty when snappable rails exist nearby", () => {
       const tile = 42 as any;