cache.service.ts

import { Injectable } from '@nestjs/common';

@Injectable()
export class CacheService {
  // In-memory cache (for tutorial purposes)
  // In production, use Redis or similar
  private cache: Map<string, { value: any; expiresAt: number }> = new Map();

  async get<T>(key: string): Promise<T | null> {
    const item = this.cache.get(key);
    
    if (!item) {
      return null;
    }

    if (Date.now() > item.expiresAt) {
      this.cache.delete(key);
      return null;
    }

    return item.value as T;
  }

  async set(key: string, value: any, ttl: number = 300): Promise<void> {
    const expiresAt = Date.now() + ttl * 1000;
    this.cache.set(key, { value, expiresAt });
  }

  async del(key: string): Promise<void> {
    this.cache.delete(key);
  }

  async clear(): Promise<void> {
    this.cache.clear();
  }
}