/**
 * 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 com.alibaba.jstorm.common.metric;

import java.util.concurrent.atomic.AtomicLong;

import com.alibaba.jstorm.common.metric.operator.convert.Convertor;
import com.alibaba.jstorm.common.metric.operator.merger.AvgMerger2;
import com.alibaba.jstorm.common.metric.operator.updater.AvgUpdater2;
import com.alibaba.jstorm.common.metric.window.Metric;
import com.alibaba.jstorm.utils.Pair;
import com.google.common.util.concurrent.AtomicDouble;

/**
 * Meter is used to compute tps
 * 
 * Attention: 1.
 * 
 * @author zhongyan.feng
 * 
 */
public class Histogram extends Metric<Double, Pair<AtomicDouble, AtomicLong>> {
    private static final long serialVersionUID = -1362345159511508074L;

    public Histogram() {
        defaultValue =
                new Pair<AtomicDouble, AtomicLong>(new AtomicDouble(0.0),
                        new AtomicLong(0));
        updater = new AvgUpdater2();
        merger = new AvgMerger2();
        convertor = new HistogramConvertor();

        init();
    }

    public static class HistogramConvertor implements
            Convertor<Pair<AtomicDouble, AtomicLong>, Double> {
        private static final long serialVersionUID = -1569170826785657226L;

        @Override
        public Double convert(Pair<AtomicDouble, AtomicLong> from) {
            // TODO Auto-generated method stub
            if (from == null) {
                return 0.0d;
            }

            if (from.getSecond().get() == 0) {
                return 0.0d;
            } else {
                return from.getFirst().get() / from.getSecond().get();
            }
        }

    }

}