Class LruEmbedCache

apps/memos-local-plugin/core/embedding/cache.ts:58–121

 * Simple LRU backed by `Map` (insertion-ordered) + promote-on-hit.
 */
export class LruEmbedCache implements EmbedCache {
  private readonly map = new Map<string, EmbeddingVector>();
  private readonly maxItems: number;
  private hits = 0;
  private misses = 0;
  private evictions = 0;

  constructor(maxItems: number) {
    if (!Number.isFinite(maxItems) || maxItems < 0) {
      throw new Error(`[embedding.cache] invalid maxItems: ${maxItems}`);
    }
    this.maxItems = Math.floor(maxItems);
  }

  get(key: string): EmbeddingVector | undefined {
    const v = this.map.get(key);
    if (v === undefined) {
      this.misses++;
      return undefined;
    }
    // Promote: delete + re-set moves the entry to the "most recent" slot.
    this.map.delete(key);
    this.map.set(key, v);
    this.hits++;
    return v;
  }

  set(key: string, vec: EmbeddingVector): void {
    if (this.maxItems === 0) return;
    if (this.map.has(key)) {
      this.map.delete(key);
    }
    this.map.set(key, vec);
    while (this.map.size > this.maxItems) {
      const oldest = this.map.keys().next().value as string | undefined;
      if (oldest === undefined) break;
      this.map.delete(oldest);
      this.evictions++;
    }
  }

  has(key: string): boolean {
    return this.map.has(key);
  }

  clear(): void {
    const hadSize = this.map.size;
    this.map.clear();
    this.hits = 0;
    this.misses = 0;
    this.evictions = 0;
    if (hadSize > 0) log.debug("cleared", { hadSize });
  }

  stats(): EmbedCacheStats {
    return {
      size: this.map.size,
      maxItems: this.maxItems,