/*
 * 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.activemq.artemis.cli.commands.messages.perf;

import java.util.function.LongSupplier;

public final class RateSampler implements Runnable {

   private final LongSupplier sampling;
   private long lastSample;
   private long lastSampleTime;
   private long rate;
   private long timeSpanNs;

   private RateSampler(final LongSupplier sampling) {
      this.sampling = sampling;
      this.timeSpanNs = 0;
      this.lastSampleTime = System.nanoTime();
      this.lastSample = sampling.getAsLong();
      this.rate = 0;
   }

   @Override
   public void run() {
      final long now = System.nanoTime();
      final long newSample = sampling.getAsLong();
      rate = newSample - lastSample;
      timeSpanNs = now - lastSampleTime;
      lastSample = newSample;
      lastSampleTime = now;
   }

   public long getLastSample() {
      return lastSample;
   }

   public long reportRate(final long reportIntervalNs) {
      return (rate * reportIntervalNs) / timeSpanNs;
   }

   public static RateSampler of(final LongSupplier sampling) {
      return new RateSampler(sampling);
   }

}
