import { Injectable, OnModuleDestroy } from '@nestjs/common';
import { Redis } from 'ioredis';

/**
 * Redis 封装：统一 key 前缀（REDIS_KEY_PREFIX），支持 JSON 读写与按前缀删除。
 * 多个 fork 项目共用一个 Redis 实例时，通过不同前缀隔离。
 */
@Injectable()
export class RedisService implements OnModuleDestroy {
  readonly prefix: string;
  private readonly client: Redis;

  constructor() {
    this.prefix = process.env.REDIS_KEY_PREFIX ?? 'sysmgr:';
    this.client = new Redis({
      host: process.env.REDIS_HOST ?? '127.0.0.1',
      port: Number(process.env.REDIS_PORT ?? 6379),
      db: Number(process.env.REDIS_DB ?? 0),
      password: process.env.REDIS_PASSWORD || undefined,
    });
  }

  private key(k: string): string {
    return this.prefix + k;
  }

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

  async setJson(key: string, value: unknown, ttlSeconds?: number): Promise<void> {
    const raw = JSON.stringify(value);
    if (ttlSeconds && ttlSeconds > 0) await this.client.set(this.key(key), raw, 'EX', ttlSeconds);
    else await this.client.set(this.key(key), raw);
  }

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

  /** 按前缀删除（SCAN 而非 KEYS，避免阻塞）。 */
  async delByPrefix(prefix: string): Promise<void> {
    const fullPrefix = this.prefix + prefix;
    let cursor = '0';
    do {
      const [next, keys] = await this.client.scan(cursor, 'MATCH', `${fullPrefix}*`, 'COUNT', 200);
      cursor = next;
      if (keys.length > 0) await this.client.del(...keys);
    } while (cursor !== '0');
  }

  async onModuleDestroy(): Promise<void> {
    await this.client.quit();
  }
}