import redis.clients.jedis.Jedis;
import redis.clients.jedis.Transaction;
import redis.clients.jedis.ZParams;
import java.util.List;
import java.util.UUID;

/**
 * @email wangiegie@gmail.com
 * @data 2017-08
 */
public class RedisRateLimiter {
  private static final String BUCKET = "BUCKET";
  private static final String BUCKET_COUNT = "BUCKET_COUNT";
  private static final String BUCKET_MONITOR = "BUCKET_MONITOR";

  static String acquireTokenFromBucket(
      Jedis jedis, int limit, long timeout) {
    String identifier = UUID.randomUUID().toString();
    long now = System.currentTimeMillis();
    Transaction transaction = jedis.multi();

    //刪除信號量
    transaction.zremrangeByScore(BUCKET_MONITOR.getBytes(), "-inf".getBytes(), String.valueOf(now - timeout).getBytes());
    ZParams params = new ZParams();
    params.weightsByDouble(1.0,0.0);
    transaction.zinterstore(BUCKET, params, BUCKET, BUCKET_MONITOR);

    //計數(shù)器自增
    transaction.incr(BUCKET_COUNT);
    List<Object> results = transaction.exec();
    long counter = (Long) results.get(results.size() - 1);

    transaction = jedis.multi();
    transaction.zadd(BUCKET_MONITOR, now, identifier);
    transaction.zadd(BUCKET, counter, identifier);
    transaction.zrank(BUCKET, identifier);
    results = transaction.exec();
    //獲取排名，判斷請求是否取得了信號量
    long rank = (Long) results.get(results.size() - 1);
    if (rank < limit) {
      return identifier;
    } else {//沒有獲取到信號量，清理之前放入redis 中垃圾數(shù)據(jù)
      transaction = jedis.multi();
      transaction.zrem(BUCKET_MONITOR, identifier);
      transaction.zrem(BUCKET, identifier);
      transaction.exec();
    }
    return null;
  }
}

@GetMapping("/")
public void index(HttpServletResponse response) throws IOException {
  Jedis jedis = jedisPool.getResource();
  String token = RedisRateLimiter.acquireTokenFromBucket(jedis, LIMIT, TIMEOUT);
  if (token == null) {
    response.sendError(500);
  }else{
    //TODO 你的業(yè)務邏輯
  }
  jedisPool.returnResource(jedis);
}

@Configuration
static class WebMvcConfigurer extends WebMvcConfigurerAdapter {
  private Logger logger = LoggerFactory.getLogger(WebMvcConfigurer.class);
  @Autowired
  private JedisPool jedisPool;

  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(new HandlerInterceptorAdapter() {
      public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
                   Object handler) throws Exception {
        HandlerMethod handlerMethod = (HandlerMethod) handler;
        Method method = handlerMethod.getMethod();
        RateLimiter rateLimiter = method.getAnnotation(RateLimiter.class);
        if (rateLimiter != null){
          int limit = rateLimiter.limit();
          int timeout = rateLimiter.timeout();
          Jedis jedis = jedisPool.getResource();
          String token = RedisRateLimiter.acquireTokenFromBucket(jedis, limit, timeout);
          if (token == null) {
            response.sendError(500);
            return false;
          }
          logger.debug("token -> {}",token);
          jedis.close();
        }
        return true;
      }
    }).addPathPatterns("/*");
  }
}

/**
 * @email wangiegie@gmail.com
 * @data 2017-08
 * 限流注解
 */

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RateLimiter {
  int limit() default 5;
  int timeout() default 1000;
}

@RateLimiter(limit = 2, timeout = 5000)
@GetMapping("/test")
public void test() {
}