Class PersistentEmbeddingCache

v3/@claude-flow/embeddings/src/persistent-cache.ts:52–397

 * SQLite-backed persistent embedding cache using sql.js (pure JS/WASM)
 */
export class PersistentEmbeddingCache {
  private db: SqlJsDatabase | null = null;
  private SQL: SqlJsStatic | null = null;
  private initialized = false;
  private dirty = false;
  private hits = 0;
  private misses = 0;
  private autoSaveTimer: ReturnType<typeof setInterval> | null = null;

  private readonly dbPath: string;
  private readonly maxSize: number;
  private readonly ttlMs: number;
  private readonly autoSaveInterval: number;

  constructor(config: PersistentCacheConfig) {
    this.dbPath = config.dbPath;
    this.maxSize = config.maxSize ?? 10000;
    this.ttlMs = config.ttlMs ?? 7 * 24 * 60 * 60 * 1000; // 7 days
    this.autoSaveInterval = config.autoSaveInterval ?? 30000; // 30 seconds
  }

  /**
   * Lazily initialize database connection
   */
  private async ensureInitialized(): Promise<void> {
    if (this.initialized) return;

    try {
      // Dynamically import sql.js
      const initSqlJs = (await import('sql.js')).default;

      // Initialize sql.js (loads WASM)
      this.SQL = await initSqlJs();

      // Ensure directory exists
      const dir = dirname(this.dbPath);
      if (!existsSync(dir)) {
        mkdirSync(dir, { recursive: true });
      }

      // Load existing database or create new
      if (existsSync(this.dbPath)) {
        const fileBuffer = readFileSync(this.dbPath);
        this.db = new this.SQL.Database(fileBuffer);
      } else {
        this.db = new this.SQL.Database();
      }

      // Create schema
      this.db.run(`
        CREATE TABLE IF NOT EXISTS embeddings (
          key TEXT PRIMARY KEY,
          embedding BLOB NOT NULL,
          dimensions INTEGER NOT NULL,
          created_at INTEGER NOT NULL,
          accessed_at INTEGER NOT NULL,
          access_count INTEGER DEFAULT 1
        )