import { Injectable, HttpException, HttpStatus } from '@nestjs/common';
import { RedisService } from '../../infrastructure/redis/redis.service';

@Injectable()
export class RateLimitService {
  constructor(private readonly redis: RedisService) {}

  async checkLimit(
    key: string,
    maxRequests: number,
    windowSeconds: number,
  ): Promise<void> {
    const count = await this.redis.incr(key);
    if (count === 1) {
      await this.redis.expire(key, windowSeconds);
    }
    if (count > maxRequests) {
      throw new HttpException(
        {
          statusCode: HttpStatus.TOO_MANY_REQUESTS,
          message: `请求过于频繁，请${windowSeconds}秒后再试`,
          retryAfter: windowSeconds,
        },
        HttpStatus.TOO_MANY_REQUESTS,
      );
    }
  }

  async loginLimit(ip: string): Promise<void> {
    const today = new Date().toISOString().split('T')[0];
    await this.checkLimit(`rate:ip:${ip}:login:${today}`, 20, 1800);
  }

  async feedbackLimit(ip: string): Promise<void> {
    await this.checkLimit(`rate:ip:${ip}:feedback:hourly`, 5, 3600);
  }

  async aiAnalysisLimit(userId: string): Promise<void> {
    const today = new Date().toISOString().split('T')[0];
    await this.checkLimit(`rate:user:${userId}:ai:daily:${today}`, 50, 86400);
  }

  async fileUploadLimit(userId: string): Promise<void> {
    await this.checkLimit(`rate:user:${userId}:upload:hourly`, 10, 3600);
  }
}