/** Kapasite sınırlı, en uzun süre kullanılmayanı (LRU) atan önbellek. */
export class LRUCache {
  constructor(capacity) {
    if (!Number.isInteger(capacity) || capacity <= 0) {
      throw new RangeError('capacity pozitif tam sayı olmalı');
    }
    this.capacity = capacity;
    this.map = new Map();
    this.hits = 0;
    this.misses = 0;
  }

  get(key) {
    if (!this.map.has(key)) {
      this.misses++;
      return undefined;
    }
    const value = this.map.get(key);
    this.map.delete(key);
    this.map.set(key, value);
    this.hits++;
    return value;
  }

  set(key, value) {
    if (this.map.has(key)) this.map.delete(key);
    this.map.set(key, value);
    if (this.map.size > this.capacity) {
      const oldest = this.map.keys().next().value;
      this.map.delete(oldest);
      return oldest;
    }
    return undefined;
  }

  get size() {
    return this.map.size;
  }

  hitRate() {
    const total = this.hits + this.misses;
    return total === 0 ? 0 : this.hits / total;
  }
}