feat: add poc

src/core/Engine.js

@@ -0,0 +1,139 @@
+import { System } from './System.js';
+import { Entity } from './Entity.js';
+import { EventBus } from './EventBus.js';
+
+/**
+ * Main game engine - manages ECS, game loop, and systems
+ */
+export class Engine {
+  constructor(canvas) {
+    this.canvas = canvas;
+    this.ctx = canvas.getContext('2d');
+    this.entities = [];
+    this.systems = [];
+    this.events = new EventBus();
+    this.running = false;
+    this.lastTime = 0;
+
+    // Set canvas size
+    this.canvas.width = 1024;
+    this.canvas.height = 768;
+
+    // Game state
+    this.deltaTime = 0;
+  }
+
+  /**
+     * Add a system to the engine
+     */
+  addSystem(system) {
+    if (system instanceof System) {
+      system.init(this);
+      this.systems.push(system);
+      // Sort by priority (lower priority runs first)
+      this.systems.sort((a, b) => a.priority - b.priority);
+    }
+    return this;
+  }
+
+  /**
+     * Emit an event locally
+     */
+  emit(event, data) {
+    this.events.emit(event, data);
+  }
+
+  /**
+     * Subscribe to an event
+     */
+  on(event, callback) {
+    return this.events.on(event, callback);
+  }
+
+  /**
+     * Create and add an entity
+     */
+  createEntity() {
+    const entity = new Entity();
+    this.entities.push(entity);
+    return entity;
+  }
+
+  /**
+     * Remove an entity
+     */
+  removeEntity(entity) {
+    const index = this.entities.indexOf(entity);
+    if (index > -1) {
+      this.entities.splice(index, 1);
+    }
+  }
+
+  /**
+     * Get all entities
+     */
+  getEntities() {
+    return this.entities.filter(e => e.active);
+  }
+
+  /**
+     * Main game loop
+     */
+  start() {
+    if (this.running) return;
+    this.running = true;
+    this.lastTime = performance.now();
+    this.gameLoop();
+  }
+
+  /**
+     * Stop the game loop
+     */
+  stop() {
+    this.running = false;
+  }
+
+  /**
+     * Game loop using requestAnimationFrame
+     */
+  gameLoop = (currentTime = 0) => {
+    if (!this.running) return;
+
+    // Calculate delta time
+    this.deltaTime = (currentTime - this.lastTime) / 1000; // Convert to seconds
+    this.lastTime = currentTime;
+
+    // Clamp delta time to prevent large jumps
+    this.deltaTime = Math.min(this.deltaTime, 0.1);
+
+    // Update all systems
+    const menuSystem = this.systems.find(s => s.name === 'MenuSystem');
+    const gameState = menuSystem ? menuSystem.getGameState() : 'playing';
+    const isPaused = gameState === 'paused' || gameState === 'start';
+
+    this.systems.forEach(system => {
+      // Skip game systems if paused/start menu (but allow MenuSystem, UISystem, and RenderSystem)
+      if (isPaused && system.name !== 'MenuSystem' && system.name !== 'UISystem' && system.name !== 'RenderSystem') {
+        return;
+      }
+      system.update(this.deltaTime, this.entities);
+    });
+
+    // Update input system's previous states at end of frame
+    const inputSystem = this.systems.find(s => s.name === 'InputSystem');
+    if (inputSystem && inputSystem.updatePreviousStates) {
+      inputSystem.updatePreviousStates();
+    }
+
+    // Continue loop
+    requestAnimationFrame(this.gameLoop);
+  }
+
+  /**
+     * Clear the canvas
+     */
+  clear() {
+    this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height);
+  }
+}
+