/** Мини-кэш с TTL и вытеснением по LRU (Map сохраняет порядок вставки). */
export class TtlCache<K, V> {
  private readonly map = new Map<K, { value: V; expires: number }>()

  constructor(
    private readonly opts: {
      max: number
      ttlMs: number
      now?: () => number
    },
  ) {}

  private now(): number {
    return (this.opts.now ?? Date.now)()
  }

  get(key: K): V | undefined {
    const hit = this.map.get(key)
    if (!hit) return undefined
    if (hit.expires <= this.now()) {
      this.map.delete(key)
      return undefined
    }
    // освежаем позицию для LRU
    this.map.delete(key)
    this.map.set(key, hit)
    return hit.value
  }

  set(key: K, value: V): void {
    this.map.delete(key)
    this.map.set(key, { value, expires: this.now() + this.opts.ttlMs })
    while (this.map.size > this.opts.max) {
      const oldest = this.map.keys().next()
      if (oldest.done) break
      this.map.delete(oldest.value)
    }
  }

  delete(key: K): void {
    this.map.delete(key)
  }

  clear(): void {
    this.map.clear()
  }

  get size(): number {
    return this.map.size
  }
}