import { BaseScene } from "./BaseScene";
import { SceneKeys } from "../SceneKeys";
import { AssetLoader, type AssetManifest } from "../utils/AssetLoader";

/**
 * 预加载场景。
 *
 * 使用 HTML overlay 显示加载进度（CSS 动画，无需 Three.js 渲染）。
 * 加载完成后自动切换到 Main 场景。
 *
 * 要加载资源，在 getManifest() 中返回资源清单即可。
 */
export class PreloaderScene extends BaseScene {
  private loader = new AssetLoader();

  constructor() {
    super(SceneKeys.Preloader);
  }

  protected onEnter(): void {
    this.showOverlay();
    this.startLoading();
  }

  /**
   * 定义资源清单。按需添加资源条目。
   *
   * 示例：
   * ```typescript
   * import logoTexture from "assets/images/logo.webp";
   * import modelFile from "assets/models/character.glb";
   *
   * return {
   *   textures: [{ key: "logo", url: logoTexture }],
   *   models: [{ key: "character", url: modelFile }],
   * };
   * ```
   */
  protected getManifest(): AssetManifest {
    return {};
  }

  private async startLoading(): Promise<void> {
    const manifest = this.getManifest();

    try {
      await this.loader.loadAll(manifest, (progress) => {
        this.updateProgress(progress);
      });
    } catch (err) {
      console.error("[PreloaderScene] Loading failed:", err);
    }

    this.updateProgress(1);
    this.setLoadingText("Ready");

    await this.delay(300);
    this.hideOverlay();
    this.goToScene(SceneKeys.Main);
  }

  private showOverlay(): void {
    const overlay = document.getElementById("loading-overlay");
    if (overlay) {
      overlay.classList.remove("hidden");
    }
  }

  private hideOverlay(): void {
    const overlay = document.getElementById("loading-overlay");
    if (overlay) {
      overlay.classList.add("hidden");
    }
  }

  private updateProgress(value: number): void {
    const bar = document.getElementById("loading-bar");
    if (bar) {
      bar.style.width = `${Math.round(value * 100)}%`;
    }
  }

  private setLoadingText(text: string): void {
    const el = document.getElementById("loading-text");
    if (el) {
      el.textContent = text;
    }
  }

  private delay(ms: number): Promise<void> {
    return new Promise((resolve) => setTimeout(resolve, ms));
  }
}