NapCatQQ/packages/napcat-common/src/lru-cache.ts

export class LRUCache<K, V> {
  private capacity: number;
  public cache: Map<K, V>;

  constructor (capacity: number) {
    this.capacity = capacity;
    this.cache = new Map<K, V>();
  }

  public get (key: K): V | undefined {
    const value = this.cache.get(key);
    if (value !== undefined) {
      // Move the accessed key to the end to mark it as most recently used
      this.cache.delete(key);
      this.cache.set(key, value);
    }
    return value;
  }

  public put (key: K, value: V): void {
    if (this.cache.has(key)) {
      // If the key already exists, move it to the end to mark it as most recently used
      this.cache.delete(key);
    } else if (this.cache.size >= this.capacity) {
      // If the cache is full, remove the least recently used key (the first one in the map)
      const firstKey = this.cache.keys().next().value;
      if (firstKey !== undefined) {
        this.cache.delete(firstKey);
      }
    }
    this.cache.set(key, value);
  }

  public resetCapacity (newCapacity: number): void {
    this.capacity = newCapacity;
    while (this.cache.size > this.capacity) {
      const firstKey = this.cache.keys().next().value;
      if (firstKey !== undefined) {
        this.cache.delete(firstKey);
      }
    }
  }
}