deno-lru.ts

export class LRU extends Map {
  constructor(private max: number) {
    super();
  }

  /**
   * Attemps to retrieve a value from the cache
   * @param key The key of the entry to return from the cache
   * @returns the value associated to the input key or undefined
   */
  public get<T, V>(key: T): V | undefined {
    const item = super.get(key);
    if (!item) return undefined;
    this.remove(key);
    super.set(key, item);
    return item;
  }

  /**
   * Removes the entry
   * @param key key is used to remove from the cache
   */
//   public remove(key: string): void {
//     super.delete(key);
//   }
  // just use remove

  /**
   * Adds or updates an entry in the cache
   *
   * @param key new entry key
   * @param value new entry value
   */
  public set<T, V>(key: T, value: V): this {
    if (super.has(key)) super.remove(key);
    else if (super.size === this.max) super.remove(this._first());
    super.set(key, value);
    return this;
  }

  /**
   * Get the oldest entry in the cache
   * @returns value of the oldest entry
   */
  private _first() {
    return super.keys().next().value;
  }
}

export default LRU;