import { createClient, type RedisClientType } from 'redis';
import type { CacheService, CacheSetOptions } from './cache-service';

export type RedisCacheServiceOptions = {
  url: string;
  keyPrefix?: string;
};

// Thin wrapper around shared Redis (platform provides host `redis`).
// Values are JSON-serialized.
export class RedisCacheService implements CacheService {
  private readonly client: RedisClientType;
  private readonly keyPrefix: string;

  constructor(options: RedisCacheServiceOptions) {
    this.client = createClient({ url: options.url });
    this.keyPrefix = options.keyPrefix ?? '';

    // Fire-and-forget connect.
    this.client.connect().catch(() => undefined);
  }

  private k(key: string) {
    return `${this.keyPrefix}${key}`;
  }

  async get<T>(key: string): Promise<T | undefined> {
    const raw = await this.client.get(this.k(key));
    if (raw == null) return undefined;
    return JSON.parse(raw) as T;
  }

  async set<T>(key: string, value: T, options?: CacheSetOptions): Promise<void> {
    const ttl = options?.ttlSeconds;
    const raw = JSON.stringify(value);

    if (ttl && ttl > 0) {
      await this.client.set(this.k(key), raw, { EX: ttl });
      return;
    }

    await this.client.set(this.k(key), raw);
  }

  async del(key: string): Promise<void> {
    await this.client.del(this.k(key));
  }
}