Set a targetable status for nukes (#1174)

## Description:

Set a targetable status for units (specifically atom bomb and hydro)
A nuke is targetable near launch and target but is untargetable mid air.
An untargetable unit is half transparent to show that it cannot be
destroyed.


![targetable](https://github.com/user-attachments/assets/cc6769ff-95ab-4294-9a8e-10f909711f68)

## 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:

Vivacious Box

src/client/graphics/layers/UnitLayer.ts

@@ -535,6 +535,11 @@ export class UnitLayer implements Layer {
     );
 
     if (unit.isActive()) {
+      const targetable = unit.targetable();
+      if (!targetable) {
+        this.context.save();
+        this.context.globalAlpha = 0.4;
+      }
       this.context.drawImage(
         sprite,
         Math.round(x - sprite.width / 2),
@@ -542,6 +547,9 @@ export class UnitLayer implements Layer {
         sprite.width,
         sprite.width,
       );
+      if (!targetable) {
+        this.context.restore();
+      }
     }
   }
 }

src/core/execution/NukeExecution.ts

@@ -13,6 +13,8 @@ import { ParabolaPathFinder } from "../pathfinding/PathFinding";
 import { PseudoRandom } from "../PseudoRandom";
 import { NukeType } from "../StatsSchemas";
 
+const NUKE_TARGETABLE_RADIUS = 120;
+
 const SPRITE_RADIUS = 16;
 
 export class NukeExecution implements Execution {
@@ -99,6 +101,7 @@ export class NukeExecution implements Execution {
         this.active = false;
         return;
       }
+      this.src = spawn;
       this.pathFinder.computeControlPoints(
         spawn,
         this.dst,
@@ -163,10 +166,31 @@ export class NukeExecution implements Execution {
       this.detonate();
       return;
     } else {
+      this.updateNukeTargetable();
       this.nuke.move(nextTile);
     }
   }
 
+  public getNuke(): Unit | null {
+    return this.nuke;
+  }
+
+  private updateNukeTargetable() {
+    if (this.nuke === null || this.nuke.targetTile() === undefined) {
+      return;
+    }
+    const targetRangeSquared = NUKE_TARGETABLE_RADIUS * NUKE_TARGETABLE_RADIUS;
+    const targetTile = this.nuke.targetTile();
+    this.nuke.setTargetable(
+      this.mg.euclideanDistSquared(this.nuke.tile(), targetTile!) <
+        targetRangeSquared ||
+        (this.src !== undefined &&
+          this.src !== null &&
+          this.mg.euclideanDistSquared(this.src, this.nuke.tile()) <
+            targetRangeSquared),
+    );
+  }
+
   private detonate() {
     if (this.nuke === null) {
       throw new Error("Not initialized");

src/core/execution/SAMLauncherExecution.ts

@@ -37,18 +37,6 @@ export class SAMLauncherExecution implements Execution {
     this.mg = mg;
   }
 
-  private nukeTargetInRange(nuke: Unit) {
-    const targetTile = nuke.targetTile();
-    if (this.sam === null || targetTile === undefined) {
-      return false;
-    }
-    const targetRangeSquared = this.targetRangeRadius * this.targetRangeRadius;
-    return (
-      this.mg.euclideanDistSquared(this.sam.tile(), targetTile) <
-      targetRangeSquared
-    );
-  }
-
   private getSingleTarget(): Unit | null {
     if (this.sam === null) return null;
     const nukes = this.mg
@@ -60,7 +48,7 @@ export class SAMLauncherExecution implements Execution {
         ({ unit }) =>
           unit.owner() !== this.player &&
           !this.player.isFriendly(unit.owner()) &&
-          this.nukeTargetInRange(unit),
+          unit.isTargetable(),
       );
 
     return (

src/core/game/Game.ts

@@ -383,6 +383,8 @@ export interface Unit {
   targetedBySAM(): boolean;
   setReachedTarget(): void;
   reachedTarget(): boolean;
+  isTargetable(): boolean;
+  setTargetable(targetable: boolean): void;
 
   // Health
   hasHealth(): boolean;

src/core/game/GameUpdates.ts

@@ -76,6 +76,7 @@ export interface UnitUpdate {
   isActive: boolean;
   reachedTarget: boolean;
   retreating: boolean;
+  targetable: boolean;
   targetUnitId?: number; // Only for trade ships
   targetTile?: TileRef; // Only for nukes
   health?: number;

src/core/game/GameView.ts

@@ -72,6 +72,10 @@ export class UnitView {
     return this.data.id;
   }
 
+  targetable(): boolean {
+    return this.data.targetable;
+  }
+
   type(): UnitType {
     return this.data.unitType;
   }

src/core/game/UnitImpl.ts

@@ -30,6 +30,8 @@ export class UnitImpl implements Unit {
   private _readyMissileCount: number = 1;
   private _patrolTile: TileRef | undefined;
   private _level: number = 1;
+  private _targetable: boolean = true;
+
   constructor(
     private _type: UnitType,
     private mg: GameImpl,
@@ -63,6 +65,17 @@ export class UnitImpl implements Unit {
     }
   }
 
+  setTargetable(targetable: boolean): void {
+    if (this._targetable !== targetable) {
+      this._targetable = targetable;
+      this.mg.addUpdate(this.toUpdate());
+    }
+  }
+
+  isTargetable(): boolean {
+    return this._targetable;
+  }
+
   setPatrolTile(tile: TileRef): void {
     this._patrolTile = tile;
   }
@@ -101,6 +114,7 @@ export class UnitImpl implements Unit {
       reachedTarget: this._reachedTarget,
       retreating: this._retreating,
       pos: this._tile,
+      targetable: this._targetable,
       lastPos: this._lastTile,
       health: this.hasHealth() ? Number(this._health) : undefined,
       constructionType: this._constructionType,