/**
    * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional information regarding
    * copyright ownership. The ASF licenses this file to you 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 org.apache.hadoop.hbase.quotas;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import com.google.common.annotations.VisibleForTesting;
  
  /**
   * This limiter will refill resources at every TimeUnit/resources interval. For example: For a
   * limiter configured with 10resources/second, then 1 resource will be refilled after every 100ms
   * (1sec/10resources)
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public class AverageIntervalRateLimiter extends RateLimiter {
    private long nextRefillTime = -1L;
  
    @Override
    public long refill(long limit) {
      final long now = EnvironmentEdgeManager.currentTime();
      if (nextRefillTime == -1) {
        // Till now no resource has been consumed.
        nextRefillTime = EnvironmentEdgeManager.currentTime();
        return limit;
      }
  
      long timeInterval = now - nextRefillTime;
      long delta = 0;
      long timeUnitInMillis = super.getTimeUnitInMillis();
      if (timeInterval >= timeUnitInMillis) {
        delta = limit;
      } else if (timeInterval > 0) {
        double r = ((double)timeInterval / (double)timeUnitInMillis) * limit;
        delta = (long)r;
      }
  
      if (delta > 0) {
        this.nextRefillTime = now;
      }
  
      return delta;
    }
  
    @Override
    public long getWaitInterval(long limit, long available, long amount) {
      if (nextRefillTime == -1) {
        return 0;
      }
  
      double r = ((double)(amount - available)) * super.getTimeUnitInMillis() / limit;
      return (long)r;
    }
  
    // This method is for strictly testing purpose only
    @VisibleForTesting
    @Override
    public void setNextRefillTime(long nextRefillTime) {
      this.nextRefillTime = nextRefillTime;
    }
  
    @VisibleForTesting
    @Override
    public long getNextRefillTime() {
      return this.nextRefillTime;
    }
  
  }