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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 *    Copyright (c) [2018] Payara Foundation and/or its affiliates. All rights reserved.
 * 
 *     The contents of this file are subject to the terms of either the GNU
 *     General Public License Version 2 only ("GPL") or the Common Development
 *     and Distribution License("CDDL") (collectively, the "License").  You
 *     may not use this file except in compliance with the License.  You can
 *     obtain a copy of the License at
 *     https://github.com/payara/Payara/blob/master/LICENSE.txt
 *     See the License for the specific
 *     language governing permissions and limitations under the License.
 * 
 *     When distributing the software, include this License Header Notice in each
 *     file and include the License file at glassfish/legal/LICENSE.txt.
 * 
 *     GPL Classpath Exception:
 *     The Payara Foundation designates this particular file as subject to the "Classpath"
 *     exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 *     file that accompanied this code.
 * 
 *     Modifications:
 *     If applicable, add the following below the License Header, with the fields
 *     enclosed by brackets [] replaced by your own identifying information:
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 *     Contributor(s):
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 *     only if the new code is made subject to such option by the copyright
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 *
 * *****************************************************************************
 * Copyright 2010-2013 Coda Hale and Yammer, Inc.
 *
 * 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
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package fish.payara.microprofile.metrics.impl;

import java.util.concurrent.atomic.LongAdder;
import javax.enterprise.inject.Vetoed;
import org.eclipse.microprofile.metrics.Histogram;
import org.eclipse.microprofile.metrics.Snapshot;

/**
 * A metric which calculates the distribution of a value.
 *
 * @see Accurately
 * computing running variance
 */
@Vetoed
public class HistogramImpl implements Histogram {

    private final Reservoir reservoir;
    private final LongAdder count;

    /**
     * Creates a new {@link HistogramImpl} using an
     * {@link ExponentiallyDecayingReservoir}.
     */
    public HistogramImpl() {
        this(new ExponentiallyDecayingReservoir());
    }

    /**
     * Creates a new {@link HistogramImpl} with the given reservoir.
     *
     * @param reservoir the reservoir to create a histogram from
     */
    public HistogramImpl(Reservoir reservoir) {
        this.reservoir = reservoir;
        this.count = new LongAdder();
    }

    /**
     * Adds a recorded value.
     *
     * @param value the length of the value
     */
    @Override
    public void update(int value) {
        update((long) value);
    }

    /**
     * Adds a recorded value.
     *
     * @param value the length of the value
     */
    @Override
    public void update(long value) {
        count.increment();
        reservoir.update(value);
    }

    /**
     * Returns the number of values recorded.
     *
     * @return the number of values recorded
     */
    @Override
    public long getCount() {
        return count.sum();
    }

    @Override
    public Snapshot getSnapshot() {
        return reservoir.getSnapshot();
    }
}