import { domtools } from '@design.estate/dees-element';

interface CachedDocument {
  url: string;
  document: any;
  lastAccessed: number;
  refCount: number;
}

export class PdfManager {
  private static cache = new Map<string, CachedDocument>();
  private static maxCacheSize = 10;
  private static pdfjsLib: any;
  private static initialized = false;

  public static async initialize() {
    if (this.initialized) return;

    // @ts-ignore
    this.pdfjsLib = await import('https://cdn.jsdelivr.net/npm/pdfjs-dist@4.0.379/+esm');
    this.pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdn.jsdelivr.net/npm/pdfjs-dist@4.0.379/build/pdf.worker.mjs';

    this.initialized = true;
  }

  public static async loadDocument(url: string): Promise<any> {
    await this.initialize();

    // Check cache first
    const cached = this.cache.get(url);
    if (cached) {
      cached.lastAccessed = Date.now();
      cached.refCount++;
      return cached.document;
    }

    // Load new document
    const loadingTask = this.pdfjsLib.getDocument(url);
    const document = await loadingTask.promise;

    // Add to cache with LRU eviction if needed
    if (this.cache.size >= this.maxCacheSize) {
      this.evictLeastRecentlyUsed();
    }

    this.cache.set(url, {
      url,
      document,
      lastAccessed: Date.now(),
      refCount: 1,
    });

    return document;
  }

  public static releaseDocument(url: string) {
    const cached = this.cache.get(url);
    if (cached) {
      cached.refCount--;
      if (cached.refCount <= 0) {
        // Don't immediately remove, keep for potential reuse
        cached.refCount = 0;
      }
    }
  }

  private static evictLeastRecentlyUsed() {
    let oldestTime = Infinity;
    let oldestKey: string | null = null;

    for (const [key, value] of this.cache.entries()) {
      // Only evict if not currently in use
      if (value.refCount === 0 && value.lastAccessed < oldestTime) {
        oldestTime = value.lastAccessed;
        oldestKey = key;
      }
    }

    if (oldestKey) {
      const cached = this.cache.get(oldestKey);
      if (cached?.document) {
        cached.document.destroy?.();
      }
      this.cache.delete(oldestKey);
    }
  }

  public static clearCache() {
    for (const cached of this.cache.values()) {
      if (cached.document) {
        cached.document.destroy?.();
      }
    }
    this.cache.clear();
  }

  public static getCacheStats() {
    return {
      size: this.cache.size,
      maxSize: this.maxCacheSize,
      entries: Array.from(this.cache.entries()).map(([url, data]) => ({
        url,
        refCount: data.refCount,
        lastAccessed: new Date(data.lastAccessed).toISOString(),
      })),
    };
  }
}