Optimize initial loading performance

src/game/scenes/lazyScenes.ts

@@ -0,0 +1,57 @@
+import Phaser from 'phaser';
+
+export type LazySceneKey = 'StoryScene' | 'BattleScene' | 'CampScene' | 'EndingScene';
+
+type LazySceneConstructor = new () => Phaser.Scene;
+
+const lazySceneLoaders: Record<LazySceneKey, () => Promise<LazySceneConstructor>> = {
+  StoryScene: () => import('./StoryScene').then((module) => module.StoryScene),
+  BattleScene: () => import('./BattleScene').then((module) => module.BattleScene),
+  CampScene: () => import('./CampScene').then((module) => module.CampScene),
+  EndingScene: () => import('./EndingScene').then((module) => module.EndingScene)
+};
+
+const pendingSceneLoads = new Map<LazySceneKey, Promise<void>>();
+
+export function isLazySceneKey(key: string): key is LazySceneKey {
+  return key === 'StoryScene' || key === 'BattleScene' || key === 'CampScene' || key === 'EndingScene';
+}
+
+export async function ensureLazyScene(game: Phaser.Game, key: LazySceneKey) {
+  if (game.scene.getScene(key)) {
+    return;
+  }
+
+  const pendingLoad = pendingSceneLoads.get(key);
+  if (pendingLoad) {
+    await pendingLoad;
+    return;
+  }
+
+  const load = lazySceneLoaders[key]().then((SceneClass) => {
+    if (!game.scene.getScene(key)) {
+      game.scene.add(key, SceneClass, false);
+    }
+  });
+  pendingSceneLoads.set(key, load);
+  await load;
+}
+
+export async function startLazyScene(scene: Phaser.Scene, key: LazySceneKey, data?: Record<string, unknown>) {
+  await ensureLazyScene(scene.game, key);
+  scene.scene.start(key, data);
+}
+
+export async function startGameScene(scene: Phaser.Scene, key: string, data?: Record<string, unknown>) {
+  if (isLazySceneKey(key)) {
+    await startLazyScene(scene, key, data);
+    return;
+  }
+
+  scene.scene.start(key, data);
+}
+
+export async function startLazySceneFromGame(game: Phaser.Game, key: LazySceneKey, data?: Record<string, unknown>) {
+  await ensureLazyScene(game, key);
+  game.scene.start(key, data);
+}