import { idbGet, idbSet, idbRemove } from './indexedDbStorage';

/**
 * Persistent cache for seen hashes (IndexedDB-backed).
 * Call init() before use.
 */
export class HashCache {
  private cache: Set<string> = new Set();
  private storageKey: string;
  private initialized = false;

  constructor(storageKey: string = 'userwallet_hash_cache') {
    this.storageKey = storageKey;
  }

  /**
   * Load cache from IndexedDB. Must be called before hasSeen / markSeen / markSeenBatch.
   */
  async init(): Promise<void> {
    if (this.initialized) {
      return;
    }
    await this.loadFromStorage();
    this.initialized = true;
  }

  /**
   * Check if a hash has been seen.
   */
  hasSeen(hash: string): boolean {
    return this.cache.has(hash);
  }

  /**
   * Mark a hash as seen (in-memory only). Use markSeenBatch to persist.
   */
  markSeen(hash: string): void {
    this.cache.add(hash);
  }

  /**
   * Mark multiple hashes as seen and persist to IndexedDB.
   */
  async markSeenBatch(hashes: string[]): Promise<void> {
    for (const hash of hashes) {
      this.cache.add(hash);
    }
    await this.saveToStorage();
  }

  /**
   * Clear the cache and remove from IndexedDB.
   */
  async clear(): Promise<void> {
    this.cache.clear();
    await idbRemove(this.storageKey);
  }

  /**
   * Get cache size.
   */
  size(): number {
    return this.cache.size;
  }

  private async loadFromStorage(): Promise<void> {
    let stored = await idbGet(this.storageKey);
    if (stored === null && typeof localStorage !== 'undefined') {
      const legacy = localStorage.getItem(this.storageKey);
      if (legacy !== null) {
        await idbSet(this.storageKey, legacy);
        localStorage.removeItem(this.storageKey);
        stored = legacy;
      }
    }
    if (stored !== null) {
      const hashes = JSON.parse(stored) as string[];
      this.cache = new Set(hashes);
    }
  }

  private async saveToStorage(): Promise<void> {
    let hashes = Array.from(this.cache);
    if (hashes.length > 10000) {
      hashes = hashes.slice(-10000);
      this.cache = new Set(hashes);
    }
    await idbSet(this.storageKey, JSON.stringify(hashes));
  }
}