allow alliance extension Fixes #491 (#1314)

## Description:

About 30s before an alliance is about to expire, both players receive a
prompt to extend the alliance. If both players agree the alliance is
extended.

## 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:

evan

src/core/execution/ExecutionManager.ts

@@ -2,6 +2,7 @@ import { Execution, Game } from "../game/Game";
 import { PseudoRandom } from "../PseudoRandom";
 import { ClientID, GameID, Intent, Turn } from "../Schemas";
 import { simpleHash } from "../Util";
+import { AllianceExtensionExecution } from "./alliance/AllianceExtensionExecution";
 import { AllianceRequestExecution } from "./alliance/AllianceRequestExecution";
 import { AllianceRequestReplyExecution } from "./alliance/AllianceRequestReplyExecution";
 import { BreakAllianceExecution } from "./alliance/BreakAllianceExecution";
@@ -111,6 +112,10 @@ export class Executor {
           this.mg.ref(intent.x, intent.y),
           intent.unit,
         );
+      case "allianceExtension": {
+        return new AllianceExtensionExecution(player, intent.recipient);
+      }
+
       case "upgrade_structure":
         return new UpgradeStructureExecution(player, intent.unitId);
       case "create_station":

src/core/execution/PlayerExecution.ts

@@ -72,10 +72,7 @@ export class PlayerExecution implements Execution {
 
     const alliances = Array.from(this.player.alliances());
     for (const alliance of alliances) {
-      if (
-        this.mg.ticks() - alliance.createdAt() >
-        this.mg.config().allianceDuration()
-      ) {
+      if (alliance.expiresAt() <= this.mg.ticks()) {
         alliance.expire();
       }
     }

src/core/execution/alliance/AllianceExtensionExecution.ts

@@ -0,0 +1,61 @@
+import {
+  Execution,
+  Game,
+  MessageType,
+  Player,
+  PlayerID,
+} from "../../game/Game";
+
+export class AllianceExtensionExecution implements Execution {
+  constructor(
+    private readonly from: Player,
+    private readonly toID: PlayerID,
+  ) {}
+
+  init(mg: Game, ticks: number): void {
+    if (!mg.hasPlayer(this.toID)) {
+      console.warn(
+        `[AllianceExtensionExecution] Player ${this.toID} not found`,
+      );
+      return;
+    }
+    const to = mg.player(this.toID);
+    const alliance = this.from.allianceWith(to);
+    if (!alliance) {
+      console.warn(
+        `[AllianceExtensionExecution] No alliance to extend between ${this.from.id()} and ${this.toID}`,
+      );
+      return;
+    }
+
+    // Mark this player's intent to extend
+    alliance.addExtensionRequest(this.from);
+
+    if (alliance.canExtend()) {
+      alliance.extend();
+
+      mg.displayMessage(
+        "alliance.renewed",
+        MessageType.ALLIANCE_ACCEPTED,
+        this.from.id(),
+      );
+      mg.displayMessage(
+        "alliance.renewed",
+        MessageType.ALLIANCE_ACCEPTED,
+        this.toID,
+      );
+    }
+  }
+
+  tick(ticks: number): void {
+    // No-op
+  }
+
+  isActive(): boolean {
+    return false;
+  }
+
+  activeDuringSpawnPhase(): boolean {
+    return false;
+  }
+}