trainsim/GameLoop.ts

import { Doodler } from "@bearmetal/doodler";
import { StateMachine } from "./state/machine.ts";
import { getContextItem } from "./lib/context.ts";

export class GameLoop<T> {
  lastTime: number;
  running: boolean;
  targetFps: number;

  constructor(targetFps: number = 60) {
    this.lastTime = performance.now();
    this.running = false;
    this.targetFps = targetFps;
  }

  async start(state: StateMachine<T>) {
    if (this.running) return;
    this.running = true;
    this.lastTime = performance.now();

    while (this.running) {
      const currentTime = performance.now();
      const deltaTime = (currentTime - this.lastTime) / 1000; // Convert to seconds
      this.lastTime = currentTime;

      try {
        // Wait for state update to complete before continuing
        await state.update(deltaTime);
      } catch (error) {
        console.error("Error in game loop:", error);
        this.stop();
        break;
      }

      // Use setTimeout to prevent immediate loop continuation
      // and allow other tasks to run
      await new Promise((resolve) => setTimeout(resolve, 0));
    }
  }

  stop() {
    this.running = false;
  }
}

// // Usage example:
// const gameState = {
//     update: async (deltaTime) => {
//         console.log(`Updating with delta time: ${deltaTime.toFixed(3)}s`);
//         // Simulate some async work
//         await new Promise(resolve => setTimeout(resolve, 16)); // ~60fps
//     }
// };

// // Create and start the loop
// const loop = new GameLoop();
// loop.start(gameState);

// // Stop the loop after 5 seconds (example)
// setTimeout(() => {
//     loop.stop();
//     console.log('Loop stopped');
// }, 5000);