import { CDN_BASE, CDN_VERSIONS } from './versions.js';

/**
 * rrweb record options
 */
export interface IRrwebRecordOptions {
  emit: (event: any) => void;
  recordCanvas?: boolean;
  recordCrossOriginIframes?: boolean;
  checkoutEveryNms?: number;
  [key: string]: any;
}

/**
 * rrweb record function type
 */
export type TRrwebRecordFn = (options: IRrwebRecordOptions) => () => void;

/**
 * Bundle type for rrweb recording library
 */
export interface IRrwebBundle {
  record: TRrwebRecordFn;
}

/**
 * rrweb-player constructor options
 */
export interface IRrwebPlayerOptions {
  target: HTMLElement;
  props: {
    events: any[];
    root?: HTMLElement;
    showController?: boolean;
    width?: number;
    height?: number;
    [key: string]: any;
  };
}

/**
 * rrweb-player instance
 */
export interface IRrwebPlayerInstance {
  play: () => Promise<void>;
  pause: () => void;
  [key: string]: any;
}

/**
 * rrweb-player constructor type
 */
export type TRrwebPlayerConstructor = new (options: IRrwebPlayerOptions) => IRrwebPlayerInstance;

/**
 * Bundle type for rrweb-player
 */
export interface IRrwebPlayerBundle {
  default: TRrwebPlayerConstructor;
}

/**
 * Singleton service for lazy-loading rrweb libraries from CDN.
 *
 * This reduces initial bundle size by loading libraries only when needed.
 * Libraries are cached after first load to avoid duplicate fetches.
 *
 * @example
 * ```typescript
 * const libLoader = SioServiceLibLoader.getInstance();
 * const rrweb = await libLoader.loadRrweb();
 * const stopFn = rrweb.record({ emit: (event) => { ... } });
 * ```
 */
export class SioServiceLibLoader {
  private static instance: SioServiceLibLoader;

  // Cached library references
  private rrwebLib: IRrwebBundle | null = null;
  private rrwebPlayerLib: IRrwebPlayerBundle | null = null;

  // Loading promises to prevent duplicate concurrent loads
  private rrwebLoadingPromise: Promise<IRrwebBundle> | null = null;
  private rrwebPlayerLoadingPromise: Promise<IRrwebPlayerBundle> | null = null;

  private constructor() {}

  /**
   * Get the singleton instance of SioServiceLibLoader
   */
  public static getInstance(): SioServiceLibLoader {
    if (!SioServiceLibLoader.instance) {
      SioServiceLibLoader.instance = new SioServiceLibLoader();
    }
    return SioServiceLibLoader.instance;
  }

  /**
   * Load rrweb recording library from CDN
   * @returns Promise resolving to rrweb module with record function
   */
  public async loadRrweb(): Promise<IRrwebBundle> {
    if (this.rrwebLib) {
      return this.rrwebLib;
    }

    if (this.rrwebLoadingPromise) {
      return this.rrwebLoadingPromise;
    }

    this.rrwebLoadingPromise = (async () => {
      const url = `${CDN_BASE}/rrweb@${CDN_VERSIONS.rrweb}/+esm`;
      const module = await import(/* @vite-ignore */ url);

      this.rrwebLib = {
        record: module.record,
      };
      return this.rrwebLib;
    })();

    return this.rrwebLoadingPromise;
  }

  /**
   * Load rrweb-player from CDN
   * @returns Promise resolving to rrweb-player module
   */
  public async loadRrwebPlayer(): Promise<IRrwebPlayerBundle> {
    if (this.rrwebPlayerLib) {
      return this.rrwebPlayerLib;
    }

    if (this.rrwebPlayerLoadingPromise) {
      return this.rrwebPlayerLoadingPromise;
    }

    this.rrwebPlayerLoadingPromise = (async () => {
      const url = `${CDN_BASE}/rrweb-player@${CDN_VERSIONS.rrwebPlayer}/+esm`;
      const module = await import(/* @vite-ignore */ url);

      // Inject rrweb-player CSS styles
      await this.injectRrwebPlayerStyles();

      this.rrwebPlayerLib = {
        default: module.default,
      };
      return this.rrwebPlayerLib;
    })();

    return this.rrwebPlayerLoadingPromise;
  }

  /**
   * Inject rrweb-player CSS styles into the document head
   */
  private async injectRrwebPlayerStyles(): Promise<void> {
    const styleId = 'rrweb-player-cdn-styles';
    if (document.getElementById(styleId)) {
      return; // Already injected
    }

    const cssUrl = `${CDN_BASE}/rrweb-player@${CDN_VERSIONS.rrwebPlayer}/dist/style.css`;
    try {
      const response = await fetch(cssUrl);
      const cssText = await response.text();

      const style = document.createElement('style');
      style.id = styleId;
      style.textContent = cssText;
      document.head.appendChild(style);
    } catch (error) {
      console.warn('Failed to load rrweb-player styles from CDN:', error);
    }
  }

  /**
   * Preload all rrweb libraries in parallel
   * Useful for warming the cache before recording is needed
   */
  public async preloadAll(): Promise<void> {
    await Promise.all([
      this.loadRrweb(),
      this.loadRrwebPlayer(),
    ]);
  }

  /**
   * Check if a specific library is already loaded
   */
  public isLoaded(library: 'rrweb' | 'rrwebPlayer'): boolean {
    switch (library) {
      case 'rrweb':
        return this.rrwebLib !== null;
      case 'rrwebPlayer':
        return this.rrwebPlayerLib !== null;
      default:
        return false;
    }
  }
}