refactor: move selection rendering to dedicated UILayer

src/client/InputHandler.ts

@@ -1,5 +1,7 @@
 import { EventBus, GameEvent } from "../core/EventBus";
 import { UserSettings } from "../core/game/UserSettings";
+import { Game } from "../core/game/Game";
+import { UnitView } from "../core/game/GameView";
 
 export class MouseUpEvent implements GameEvent {
   constructor(
@@ -8,6 +10,16 @@ export class MouseUpEvent implements GameEvent {
   ) {}
 }
 
+/**
+ * Event emitted when a unit is selected or deselected
+ */
+export class UnitSelectionEvent implements GameEvent {
+  constructor(
+    public readonly unit: UnitView | null,
+    public readonly isSelected: boolean,
+  ) {}
+}
+
 export class MouseDownEvent implements GameEvent {
   constructor(
     public readonly x: number,

src/client/graphics/GameRenderer.ts

@@ -14,6 +14,7 @@ import { ControlPanel } from "./layers/ControlPanel";
 import { UIState } from "./UIState";
 import { BuildMenu } from "./layers/BuildMenu";
 import { UnitLayer } from "./layers/UnitLayer";
+import { UILayer } from "./layers/UILayer";
 import { StructureLayer } from "./layers/StructureLayer";
 import { PlayerInfoOverlay } from "./layers/PlayerInfoOverlay";
 import { consolex } from "../../core/Consolex";
@@ -118,6 +119,7 @@ export function createRenderer(
     new TerritoryLayer(game, eventBus),
     new StructureLayer(game, eventBus),
     new UnitLayer(game, eventBus, clientID, transformHandler),
+    new UILayer(game, eventBus, clientID, transformHandler),
     new NameLayer(game, transformHandler, clientID),
     eventsDisplay,
     buildMenu,

src/client/graphics/SelectedUnits.ts

@@ -1,94 +0,0 @@
-import { EventBus, GameEvent } from "../../core/EventBus";
-import { UnitType } from "../../core/game/Game";
-import { UnitView } from "../../core/game/GameView";
-
-/**
- * Event emitted when a unit is selected or deselected
- */
-export class UnitSelectionEvent implements GameEvent {
-  constructor(
-    public readonly unit: UnitView | null,
-    public readonly isSelected: boolean,
-  ) {}
-}
-
-/**
- * Manages the currently selected units in the game
- */
-export class SelectedUnits {
-  private selectedUnit: UnitView | null = null;
-
-  constructor(private eventBus: EventBus) {}
-
-  /**
-   * Select a unit. Deselects any previously selected unit.
-   * @param unit The unit to select
-   * @returns true if the selection changed, false otherwise
-   */
-  selectUnit(unit: UnitView): boolean {
-    if (this.selectedUnit === unit) {
-      return false;
-    }
-
-    if (this.selectedUnit) {
-      this.deselectCurrentUnit();
-    }
-
-    this.selectedUnit = unit;
-    this.eventBus.emit(new UnitSelectionEvent(unit, true));
-    return true;
-  }
-
-  /**
-   * Deselect the currently selected unit, if any
-   * @returns true if a unit was deselected, false otherwise
-   */
-  deselectCurrentUnit(): boolean {
-    if (!this.selectedUnit) {
-      return false;
-    }
-
-    const unit = this.selectedUnit;
-    this.selectedUnit = null;
-    this.eventBus.emit(new UnitSelectionEvent(unit, false));
-    return true;
-  }
-
-  /**
-   * Toggle selection for the given unit
-   * @param unit The unit to toggle selection for
-   * @returns true if the unit is now selected, false if it was deselected
-   */
-  toggleUnitSelection(unit: UnitView): boolean {
-    if (this.selectedUnit === unit) {
-      this.deselectCurrentUnit();
-      return false;
-    } else {
-      this.selectUnit(unit);
-      return true;
-    }
-  }
-
-  /**
-   * Get the currently selected unit, if any
-   */
-  getSelectedUnit(): UnitView | null {
-    return this.selectedUnit;
-  }
-
-  /**
-   * Check if the given unit is currently selected
-   * @param unit The unit to check
-   */
-  isSelected(unit: UnitView): boolean {
-    return this.selectedUnit === unit;
-  }
-
-  /**
-   * Check if a unit of the specified type is currently selected
-   * @param type The unit type to check for
-   */
-  hasSelectedUnitOfType(type: UnitType): boolean {
-    return this.selectedUnit !== null && this.selectedUnit.type() === type;
-  }
-}

src/client/graphics/layers/UILayer.ts

@@ -0,0 +1,207 @@
+import { Colord } from "colord";
+import { Theme } from "../../../core/configuration/Config";
+import { UnitType } from "../../../core/game/Game";
+import { Layer } from "./Layer";
+import { EventBus } from "../../../core/EventBus";
+import { ClientID } from "../../../core/Schemas";
+import { GameView, UnitView } from "../../../core/game/GameView";
+import { UnitSelectionEvent } from "../../InputHandler";
+import { TransformHandler } from "../TransformHandler";
+
+/**
+ * Layer responsible for drawing UI elements that overlay the game
+ * such as selection boxes, health bars, etc.
+ */
+export class UILayer implements Layer {
+  private canvas: HTMLCanvasElement;
+  private context: CanvasRenderingContext2D;
+
+  private theme: Theme = null;
+  private selectionAnimTime = 0;
+
+  // Keep track of currently selected unit
+  private selectedUnit: UnitView | null = null;
+
+  // Keep track of previous selection box position for cleanup
+  private lastSelectionBoxCenter: {
+    x: number;
+    y: number;
+    size: number;
+  } | null = null;
+
+  // Visual settings for selection
+  private readonly SELECTION_BOX_SIZE = 6; // Size of the selection box (should be larger than the warship)
+
+  constructor(
+    private game: GameView,
+    private eventBus: EventBus,
+    private clientID: ClientID,
+    private transformHandler: TransformHandler,
+  ) {
+    this.theme = game.config().theme();
+  }
+
+  shouldTransform(): boolean {
+    return true;
+  }
+
+  tick() {
+    // Update the selection animation time
+    this.selectionAnimTime = (this.selectionAnimTime + 1) % 60;
+
+    // If there's a selected warship, redraw to update the selection box animation
+    if (this.selectedUnit && this.selectedUnit.type() === UnitType.Warship) {
+      this.drawSelectionBox(this.selectedUnit);
+    }
+  }
+
+  init() {
+    this.eventBus.on(UnitSelectionEvent, (e) => this.onUnitSelection(e));
+    this.redraw();
+  }
+
+  renderLayer(context: CanvasRenderingContext2D) {
+    context.drawImage(
+      this.canvas,
+      -this.game.width() / 2,
+      -this.game.height() / 2,
+      this.game.width(),
+      this.game.height(),
+    );
+  }
+
+  redraw() {
+    this.canvas = document.createElement("canvas");
+    this.context = this.canvas.getContext("2d");
+
+    this.canvas.width = this.game.width();
+    this.canvas.height = this.game.height();
+  }
+
+  /**
+   * Handle the unit selection event
+   */
+  private onUnitSelection(event: UnitSelectionEvent) {
+    if (event.isSelected) {
+      this.selectedUnit = event.unit;
+      if (event.unit && event.unit.type() === UnitType.Warship) {
+        this.drawSelectionBox(event.unit);
+      }
+    } else {
+      if (this.selectedUnit === event.unit) {
+        // Clear the selection box
+        if (this.lastSelectionBoxCenter) {
+          const { x, y, size } = this.lastSelectionBoxCenter;
+          this.clearSelectionBox(x, y, size);
+          this.lastSelectionBoxCenter = null;
+        }
+        this.selectedUnit = null;
+      }
+    }
+  }
+
+  /**
+   * Clear the selection box at a specific position
+   */
+  private clearSelectionBox(x: number, y: number, size: number) {
+    for (let px = x - size; px <= x + size; px++) {
+      for (let py = y - size; py <= y + size; py++) {
+        if (
+          px === x - size ||
+          px === x + size ||
+          py === y - size ||
+          py === y + size
+        ) {
+          this.clearCell(px, py);
+        }
+      }
+    }
+  }
+
+  /**
+   * Draw a selection box around the given unit
+   */
+  public drawSelectionBox(unit: UnitView) {
+    if (!unit || !unit.isActive()) {
+      return;
+    }
+
+    // Use the configured selection box size
+    const selectionSize = this.SELECTION_BOX_SIZE;
+
+    // Calculate pulsating effect based on animation time (25% variation in opacity)
+    const baseOpacity = 200;
+    const pulseAmount = 55;
+    const opacity =
+      baseOpacity + Math.sin(this.selectionAnimTime * 0.1) * pulseAmount;
+
+    // Get the unit's owner color for the box
+    const ownerColor = this.theme.territoryColor(unit.owner().info());
+
+    // Create a brighter version of the owner color for the selection
+    const selectionColor = ownerColor.lighten(0.2);
+
+    // Get current center position
+    const center = unit.tile();
+    const centerX = this.game.x(center);
+    const centerY = this.game.y(center);
+
+    // Clear previous selection box if it exists and is different from current position
+    if (
+      this.lastSelectionBoxCenter &&
+      (this.lastSelectionBoxCenter.x !== centerX ||
+        this.lastSelectionBoxCenter.y !== centerY)
+    ) {
+      const lastSize = this.lastSelectionBoxCenter.size;
+      const lastX = this.lastSelectionBoxCenter.x;
+      const lastY = this.lastSelectionBoxCenter.y;
+
+      // Clear the previous selection box
+      this.clearSelectionBox(lastX, lastY, lastSize);
+    }
+
+    // Draw the selection box
+    for (let x = centerX - selectionSize; x <= centerX + selectionSize; x++) {
+      for (let y = centerY - selectionSize; y <= centerY + selectionSize; y++) {
+        // Only draw if it's on the border (not inside or outside the box)
+        if (
+          x === centerX - selectionSize ||
+          x === centerX + selectionSize ||
+          y === centerY - selectionSize ||
+          y === centerY + selectionSize
+        ) {
+          // Create a dashed effect by only drawing some pixels
+          const dashPattern = (x + y) % 2 === 0;
+          if (dashPattern) {
+            this.paintCell(x, y, selectionColor, opacity);
+          }
+        }
+      }
+    }
+
+    // Store current selection box position for next cleanup
+    this.lastSelectionBoxCenter = {
+      x: centerX,
+      y: centerY,
+      size: selectionSize,
+    };
+  }
+
+  /**
+   * Draw health bar for a unit (placeholder for future implementation)
+   */
+  public drawHealthBar(unit: UnitView) {
+    // This is a placeholder for future health bar implementation
+    // It would draw a health bar above units that have health
+  }
+
+  paintCell(x: number, y: number, color: Colord, alpha: number) {
+    this.clearCell(x, y);
+    this.context.fillStyle = color.alpha(alpha / 255).toRgbString();
+    this.context.fillRect(x, y, 1, 1);
+  }
+
+  clearCell(x: number, y: number) {
+    this.context.clearRect(x, y, 1, 1);
+  }
+}

src/client/graphics/layers/UnitLayer.ts

@@ -3,7 +3,11 @@ import { Theme } from "../../../core/configuration/Config";
 import { Unit, UnitType, Player } from "../../../core/game/Game";
 import { Layer } from "./Layer";
 import { EventBus } from "../../../core/EventBus";
-import { AlternateViewEvent, MouseUpEvent } from "../../InputHandler";
+import {
+  AlternateViewEvent,
+  MouseUpEvent,
+  UnitSelectionEvent,
+} from "../../InputHandler";
 import { ClientID } from "../../../core/Schemas";
 import { GameView, PlayerView, UnitView } from "../../../core/game/GameView";
 import {
@@ -12,7 +16,6 @@ import {
   TileRef,
 } from "../../../core/game/GameMap";
 import { GameUpdateType } from "../../../core/game/GameUpdates";
-import { SelectedUnits, UnitSelectionEvent } from "../SelectedUnits";
 import { TransformHandler } from "../TransformHandler";
 
 enum Relationship {
@@ -35,10 +38,11 @@ export class UnitLayer implements Layer {
 
   private oldShellTile = new Map<UnitView, TileRef>();
 
-  private selectedUnits: SelectedUnits;
-  private selectionAnimTime = 0;
   private transformHandler: TransformHandler;
 
+  // Selected unit property as suggested in the review comment
+  private selectedUnit: UnitView | null = null;
+
   // Configuration for unit selection
   private readonly WARSHIP_SELECTION_RADIUS = 3; // Radius in game cells for warship selection hit zone
 
@@ -49,7 +53,6 @@ export class UnitLayer implements Layer {
     transformHandler: TransformHandler,
   ) {
     this.theme = game.config().theme();
-    this.selectedUnits = new SelectedUnits(eventBus);
     this.transformHandler = transformHandler;
   }
 
@@ -64,20 +67,12 @@ export class UnitLayer implements Layer {
     this.game.updatesSinceLastTick()?.[GameUpdateType.Unit]?.forEach((unit) => {
       this.onUnitEvent(this.game.unit(unit.id));
     });
-
-    // Update the selection animation time
-    this.selectionAnimTime = (this.selectionAnimTime + 1) % 60;
-
-    // If there's a selected warship, redraw to update the selection box animation
-    if (this.selectedUnits.hasSelectedUnitOfType(UnitType.Warship)) {
-      this.redrawSelectedUnit(this.selectedUnits.getSelectedUnit());
-    }
   }
 
   init() {
     this.eventBus.on(AlternateViewEvent, (e) => this.onAlternativeViewEvent(e));
     this.eventBus.on(MouseUpEvent, (e) => this.onMouseUp(e));
-    this.eventBus.on(UnitSelectionEvent, (e) => this.onUnitSelection(e));
+    this.eventBus.on(UnitSelectionEvent, (e) => this.onUnitSelectionChange(e));
     this.redraw();
   }
 
@@ -116,48 +111,29 @@ export class UnitLayer implements Layer {
     const nearbyWarships = this.findWarshipsNearCell(cell);
 
     if (nearbyWarships.length > 0) {
-      // Select/deselect the closest warship
-      this.selectedUnits.toggleUnitSelection(nearbyWarships[0]);
-    } else if (this.selectedUnits.getSelectedUnit()) {
+      // Toggle selection of the closest warship
+      const clickedUnit = nearbyWarships[0];
+      if (this.selectedUnit === clickedUnit) {
+        // Deselect if already selected
+        this.eventBus.emit(new UnitSelectionEvent(clickedUnit, false));
+      } else {
+        // Select the new unit
+        this.eventBus.emit(new UnitSelectionEvent(clickedUnit, true));
+      }
+    } else if (this.selectedUnit) {
       // If clicked elsewhere and there's a selection, deselect it
-      this.selectedUnits.deselectCurrentUnit();
+      this.eventBus.emit(new UnitSelectionEvent(this.selectedUnit, false));
     }
   }
 
   /**
-   * Clear the selection box at a specific position
+   * Handle unit selection changes
    */
-  private clearSelectionBox(x: number, y: number, size: number) {
-    for (let px = x - size; px <= x + size; px++) {
-      for (let py = y - size; py <= y + size; py++) {
-        if (
-          px === x - size ||
-          px === x + size ||
-          py === y - size ||
-          py === y + size
-        ) {
-          this.clearCell(px, py);
-        }
-      }
-    }
-  }
-
-  private onUnitSelection(event: UnitSelectionEvent) {
-    if (event.unit && event.unit.type() === UnitType.Warship) {
-      if (event.isSelected) {
-        // Highlight the selected warship
-        this.redrawSelectedUnit(event.unit);
-      } else {
-        // Remove the highlight
-        this.onUnitEvent(event.unit);
-
-        // Also clear any lingering selection box
-        if (this.lastSelectionBoxCenter) {
-          const { x, y, size } = this.lastSelectionBoxCenter;
-          this.clearSelectionBox(x, y, size);
-          this.lastSelectionBoxCenter = null;
-        }
-      }
+  private onUnitSelectionChange(event: UnitSelectionEvent) {
+    if (event.isSelected) {
+      this.selectedUnit = event.unit;
+    } else if (this.selectedUnit === event.unit) {
+      this.selectedUnit = null;
     }
   }
 
@@ -166,24 +142,8 @@ export class UnitLayer implements Layer {
    * If the selected unit is removed from the game, deselect it
    */
   private handleUnitDeactivation(unit: UnitView) {
-    if (this.selectedUnits.isSelected(unit) && !unit.isActive()) {
-      // Clear the selection box before deselecting
-      if (
-        this.lastSelectionBoxCenter &&
-        this.lastSelectionBoxCenter.unit === unit
-      ) {
-        const { x, y, size } = this.lastSelectionBoxCenter;
-        this.clearSelectionBox(x, y, size);
-        this.lastSelectionBoxCenter = null;
-      }
-
-      this.selectedUnits.deselectCurrentUnit();
-    }
-  }
-
-  private redrawSelectedUnit(unit: UnitView) {
-    if (unit && unit.type() === UnitType.Warship && unit.isActive()) {
-      this.onUnitEvent(unit);
+    if (this.selectedUnit === unit && !unit.isActive()) {
+      this.eventBus.emit(new UnitSelectionEvent(unit, false));
     }
   }
 
@@ -308,98 +268,6 @@ export class UnitLayer implements Layer {
         255,
       );
     }
-
-    // If this is a selected warship, draw the selection box
-    if (this.selectedUnits.isSelected(unit)) {
-      this.drawSelectionBox(unit);
-    }
-  }
-
-  // Keep track of previous selection box positions for cleanup
-  private lastSelectionBoxCenter: {
-    unit: UnitView;
-    x: number;
-    y: number;
-    size: number;
-  } | null = null;
-
-  // Visual settings for selection
-  private readonly SELECTION_BOX_SIZE = 6; // Size of the selection box (should be larger than the warship)
-
-  /**
-   * Draw a selection box around the warship
-   */
-  private drawSelectionBox(unit: UnitView) {
-    // Use the configured selection box size
-    const selectionSize = this.SELECTION_BOX_SIZE;
-
-    // Calculate pulsating effect based on animation time (25% variation in opacity)
-    const baseOpacity = 200;
-    const pulseAmount = 55;
-    const opacity =
-      baseOpacity + Math.sin(this.selectionAnimTime * 0.1) * pulseAmount;
-
-    // Get the warship's owner color for the box
-    const ownerColor = this.theme.territoryColor(unit.owner().info());
-
-    // Create a brighter version of the owner color for the selection
-    const selectionColor = ownerColor.lighten(0.2);
-
-    // Get current center position
-    const center = unit.tile();
-    const centerX = this.game.x(center);
-    const centerY = this.game.y(center);
-
-    // Clear previous selection box if it exists and is different from current position
-    if (
-      this.lastSelectionBoxCenter &&
-      (this.lastSelectionBoxCenter.x !== centerX ||
-        this.lastSelectionBoxCenter.y !== centerY ||
-        this.lastSelectionBoxCenter.unit !== unit)
-    ) {
-      const lastSize = this.lastSelectionBoxCenter.size;
-      const lastX = this.lastSelectionBoxCenter.x;
-      const lastY = this.lastSelectionBoxCenter.y;
-
-      // Clear the previous selection box
-      this.clearSelectionBox(lastX, lastY, lastSize);
-
-      // We don't need to redraw the territory since the unit layer sits on top of the territory layer
-      // and clearing just the selection box pixels won't affect the territory underneath
-    }
-
-    // Draw the selection box
-    for (let x = centerX - selectionSize; x <= centerX + selectionSize; x++) {
-      for (let y = centerY - selectionSize; y <= centerY + selectionSize; y++) {
-        // Only draw if it's on the border (not inside or outside the box)
-        if (
-          x === centerX - selectionSize ||
-          x === centerX + selectionSize ||
-          y === centerY - selectionSize ||
-          y === centerY + selectionSize
-        ) {
-          // Create a dashed effect by only drawing some pixels
-          const dashPattern = (x + y) % 2 === 0;
-          if (dashPattern) {
-            this.paintCell(
-              x,
-              y,
-              this.relationship(unit),
-              selectionColor,
-              opacity,
-            );
-          }
-        }
-      }
-    }
-
-    // Store current selection box position for next cleanup
-    this.lastSelectionBoxCenter = {
-      unit,
-      x: centerX,
-      y: centerY,
-      size: selectionSize,
-    };
   }
 
   private handleShellEvent(unit: UnitView) {