feat(core): 添加持久化实体支持跨场景迁移

实现实体生命周期策略，允许标记实体为持久化，在场景切换时自动迁移到新场景。主要变更： - 新增 EEntityLifecyclePolicy 枚举（SceneLocal/Persistent） - Entity 添加 setPersistent()、setSceneLocal()、isPersistent API - Scene 添加 findPersistentEntities()、extractPersistentEntities()、receiveMigratedEntities() - SceneManager.setScene() 自动处理持久化实体迁移 - 添加完整的中英文文档和 21 个测试用例
2025-12-05 22:46:53 +08:00
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+# Scene Management
+
+In the ECS architecture, a Scene is a container for the game world, responsible for managing the lifecycle of entities, systems, and components. Scenes provide a complete ECS runtime environment.
+
+## Basic Concepts
+
+Scene is the core container of the ECS framework, providing:
+- Entity creation, management, and destruction
+- System registration and execution scheduling
+- Component storage and querying
+- Event system support
+- Performance monitoring and debugging information
+
+## Scene Management Options
+
+ECS Framework provides two scene management approaches:
+
+1. **[SceneManager](./scene-manager)** - Suitable for 95% of game applications
+   - Single-player games, simple multiplayer games, mobile games
+   - Lightweight, simple and intuitive API
+   - Supports scene transitions
+
+2. **[WorldManager](./world-manager)** - Suitable for advanced multi-world isolation scenarios
+   - MMO game servers, game room systems
+   - Multi-World management, each World can contain multiple scenes
+   - Completely isolated independent environments
+
+This document focuses on the usage of the Scene class itself. For detailed information about scene managers, please refer to the corresponding documentation.
+
+## Creating a Scene
+
+### Inheriting the Scene Class
+
+**Recommended: Inherit the Scene class to create custom scenes**
+
+```typescript
+import { Scene, EntitySystem } from '@esengine/ecs-framework';
+
+class GameScene extends Scene {
+  protected initialize(): void {
+    // Set scene name
+    this.name = "GameScene";
+
+    // Add systems
+    this.addSystem(new MovementSystem());
+    this.addSystem(new RenderSystem());
+    this.addSystem(new PhysicsSystem());
+
+    // Create initial entities
+    this.createInitialEntities();
+  }
+
+  private createInitialEntities(): void {
+    // Create player
+    const player = this.createEntity("Player");
+    player.addComponent(new Position(400, 300));
+    player.addComponent(new Health(100));
+    player.addComponent(new PlayerController());
+
+    // Create enemies
+    for (let i = 0; i < 5; i++) {
+      const enemy = this.createEntity(`Enemy_${i}`);
+      enemy.addComponent(new Position(Math.random() * 800, Math.random() * 600));
+      enemy.addComponent(new Health(50));
+      enemy.addComponent(new EnemyAI());
+    }
+  }
+
+  public onStart(): void {
+    console.log("Game scene started");
+    // Logic when scene starts
+  }
+
+  public unload(): void {
+    console.log("Game scene unloaded");
+    // Cleanup logic when scene unloads
+  }
+}
+```
+
+### Using Scene Configuration
+
+```typescript
+import { ISceneConfig } from '@esengine/ecs-framework';
+
+const config: ISceneConfig = {
+  name: "MainGame",
+  enableEntityDirectUpdate: false
+};
+
+class ConfiguredScene extends Scene {
+  constructor() {
+    super(config);
+  }
+}
+```
+
+## Scene Lifecycle
+
+Scene provides complete lifecycle management:
+
+```typescript
+class ExampleScene extends Scene {
+  protected initialize(): void {
+    // Scene initialization: setup systems and initial entities
+    console.log("Scene initializing");
+  }
+
+  public onStart(): void {
+    // Scene starts running: game logic begins execution
+    console.log("Scene starting");
+  }
+
+  public unload(): void {
+    // Scene unloading: cleanup resources
+    console.log("Scene unloading");
+  }
+}
+
+// Using scenes (lifecycle automatically managed by framework)
+const scene = new ExampleScene();
+// Scene's initialize(), begin(), update(), end() are automatically called by the framework
+```
+
+**Lifecycle Methods**:
+
+1. `initialize()` - Scene initialization, setup systems and initial entities
+2. `begin()` / `onStart()` - Scene starts running
+3. `update()` - Per-frame update (called by scene manager)
+4. `end()` / `unload()` - Scene unloading, cleanup resources
+
+## Entity Management
+
+### Creating Entities
+
+```typescript
+class EntityScene extends Scene {
+  createGameEntities(): void {
+    // Create single entity
+    const player = this.createEntity("Player");
+
+    // Batch create entities (high performance)
+    const bullets = this.createEntities(100, "Bullet");
+
+    // Add components to batch-created entities
+    bullets.forEach((bullet, index) => {
+      bullet.addComponent(new Position(index * 10, 100));
+      bullet.addComponent(new Velocity(Math.random() * 200 - 100, -300));
+    });
+  }
+}
+```
+
+### Finding Entities
+
+```typescript
+class SearchScene extends Scene {
+  findEntities(): void {
+    // Find by name
+    const player = this.findEntity("Player");
+    const player2 = this.getEntityByName("Player"); // Alias method
+
+    // Find by ID
+    const entity = this.findEntityById(123);
+
+    // Find by tag
+    const enemies = this.findEntitiesByTag(2);
+    const enemies2 = this.getEntitiesByTag(2); // Alias method
+
+    if (player) {
+      console.log(`Found player: ${player.name}`);
+    }
+
+    console.log(`Found ${enemies.length} enemies`);
+  }
+}
+```
+
+### Destroying Entities
+
+```typescript
+class DestroyScene extends Scene {
+  cleanupEntities(): void {
+    // Destroy all entities
+    this.destroyAllEntities();
+
+    // Single entity destruction through the entity itself
+    const enemy = this.findEntity("Enemy_1");
+    if (enemy) {
+      enemy.destroy(); // Entity is automatically removed from the scene
+    }
+  }
+}
+```
+
+## System Management
+
+### Adding and Removing Systems
+
+```typescript
+class SystemScene extends Scene {
+  protected initialize(): void {
+    // Add systems
+    const movementSystem = new MovementSystem();
+    this.addSystem(movementSystem);
+
+    // Set system update order
+    movementSystem.updateOrder = 1;
+
+    // Add more systems
+    this.addSystem(new PhysicsSystem());
+    this.addSystem(new RenderSystem());
+  }
+
+  public removeUnnecessarySystems(): void {
+    // Get system
+    const physicsSystem = this.getEntityProcessor(PhysicsSystem);
+
+    // Remove system
+    if (physicsSystem) {
+      this.removeSystem(physicsSystem);
+    }
+  }
+}
+```
+
+## Event System
+
+Scene has a built-in type-safe event system:
+
+```typescript
+class EventScene extends Scene {
+  protected initialize(): void {
+    // Listen to events
+    this.eventSystem.on('player_died', this.onPlayerDied.bind(this));
+    this.eventSystem.on('enemy_spawned', this.onEnemySpawned.bind(this));
+    this.eventSystem.on('level_complete', this.onLevelComplete.bind(this));
+  }
+
+  private onPlayerDied(data: any): void {
+    console.log('Player died event');
+    // Handle player death
+  }
+
+  private onEnemySpawned(data: any): void {
+    console.log('Enemy spawned event');
+    // Handle enemy spawn
+  }
+
+  private onLevelComplete(data: any): void {
+    console.log('Level complete event');
+    // Handle level completion
+  }
+
+  public triggerGameEvent(): void {
+    // Send event (synchronous)
+    this.eventSystem.emitSync('custom_event', {
+      message: "This is a custom event",
+      timestamp: Date.now()
+    });
+
+    // Send event (asynchronous)
+    this.eventSystem.emit('async_event', {
+      data: "Async event data"
+    });
+  }
+}
+```
+
+## Best Practices
+
+### 1. Scene Responsibility Separation
+
+```typescript
+// Good scene design - clear responsibilities
+class MenuScene extends Scene {
+  // Only handles menu-related logic
+}
+
+class GameScene extends Scene {
+  // Only handles gameplay logic
+}
+
+class InventoryScene extends Scene {
+  // Only handles inventory logic
+}
+
+// Avoid this design - mixed responsibilities
+class MegaScene extends Scene {
+  // Contains menu, game, inventory, and all other logic
+}
+```
+
+### 2. Proper System Organization
+
+```typescript
+class OrganizedScene extends Scene {
+  protected initialize(): void {
+    // Add systems by function and dependencies
+    this.addInputSystems();
+    this.addLogicSystems();
+    this.addRenderSystems();
+  }
+
+  private addInputSystems(): void {
+    this.addSystem(new InputSystem());
+  }
+
+  private addLogicSystems(): void {
+    this.addSystem(new MovementSystem());
+    this.addSystem(new PhysicsSystem());
+    this.addSystem(new CollisionSystem());
+  }
+
+  private addRenderSystems(): void {
+    this.addSystem(new RenderSystem());
+    this.addSystem(new UISystem());
+  }
+}
+```
+
+### 3. Resource Management
+
+```typescript
+class ResourceScene extends Scene {
+  private textures: Map<string, any> = new Map();
+  private sounds: Map<string, any> = new Map();
+
+  protected initialize(): void {
+    this.loadResources();
+  }
+
+  private loadResources(): void {
+    // Load resources needed by the scene
+    this.textures.set('player', this.loadTexture('player.png'));
+    this.sounds.set('bgm', this.loadSound('bgm.mp3'));
+  }
+
+  public unload(): void {
+    // Cleanup resources
+    this.textures.clear();
+    this.sounds.clear();
+    console.log('Scene resources cleaned up');
+  }
+
+  private loadTexture(path: string): any {
+    // Load texture
+    return null;
+  }
+
+  private loadSound(path: string): any {
+    // Load sound
+    return null;
+  }
+}
+```
+
+## Next Steps
+
+- Learn about [SceneManager](./scene-manager) - Simple scene management for most games
+- Learn about [WorldManager](./world-manager) - For scenarios requiring multi-world isolation
+- Learn about [Persistent Entity](./persistent-entity) - Keep entities across scene transitions (v2.2.22+)
+
+Scene is the core container of the ECS framework. Proper scene management makes your game architecture clearer, more modular, and easier to maintain.