content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.csp.sentinel.cluster.flow.statistic.limit;
  
  import java.util.List;
  import java.util.concurrent.atomic.LongAdder;
  
  import com.alibaba.csp.sentinel.slots.statistic.base.LeapArray;
  import com.alibaba.csp.sentinel.slots.statistic.base.UnaryLeapArray;
  import com.alibaba.csp.sentinel.util.AssertUtil;
  
  /**
   * @author Eric Zhao
   * @since 1.4.1
   */
  public class RequestLimiter {
  
      private double qpsAllowed;
  
      private final LeapArray<LongAdder> data;
  
      public RequestLimiter(double qpsAllowed) {
          this(new UnaryLeapArray(10, 1000), qpsAllowed);
      }
  
      RequestLimiter(LeapArray<LongAdder> data, double qpsAllowed) {
          AssertUtil.isTrue(qpsAllowed >= 0, "max allowed QPS should > 0");
          this.data = data;
          this.qpsAllowed = qpsAllowed;
      }
  
      public void increment() {
          data.currentWindow().value().increment();
      }
  
      public void add(int x) {
          data.currentWindow().value().add(x);
      }
  
      public long getSum() {
          data.currentWindow();
          long success = 0;
  
          List<LongAdder> list = data.values();
          for (LongAdder window : list) {
              success += window.sum();
          }
          return success;
      }
  
      public double getQps() {
          return getSum() / data.getIntervalInSecond();
      }
  
      public double getQpsAllowed() {
          return qpsAllowed;
      }
  
      public boolean canPass() {
          return getQps() + 1 <= qpsAllowed;
      }
  
      public RequestLimiter setQpsAllowed(double qpsAllowed) {
          this.qpsAllowed = qpsAllowed;
          return this;
      }
  
      public boolean tryPass() {
          if (canPass()) {
              add(1);
              return true;
          }
          return false;
      }
  }
  