import type { CacheAdapter } from "../types";

export class LruCache<K, V> implements CacheAdapter<K, V> {
  private readonly maxEntries: number;
  private readonly map = new Map<K, V>();

  constructor(maxEntries: number) {
    if (!Number.isInteger(maxEntries) || maxEntries <= 0) {
      throw new Error("LruCache maxEntries must be a positive integer.");
    }

    this.maxEntries = maxEntries;
  }

  get(key: K): V | undefined {
    if (!this.map.has(key)) {
      return undefined;
    }

    const value = this.map.get(key) as V;
    this.map.delete(key);
    this.map.set(key, value);
    return value;
  }

  set(key: K, value: V): void {
    if (this.map.has(key)) {
      this.map.delete(key);
    }

    this.map.set(key, value);

    if (this.map.size > this.maxEntries) {
      const oldestKey = this.map.keys().next().value;
      if (oldestKey !== undefined) {
        this.map.delete(oldestKey);
      }
    }
  }

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

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

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