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/**
 * Copyright (c) 2012, University of Konstanz, Distributed Systems Group
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * * Neither the name of the University of Konstanz nor the
 * names of its contributors may be used to endorse or promote products
 * derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL  BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.perfidix.meter;

/**
 * This class measures the number of threads in the runtime.
 * 
 * @author Sebastian Graf, University of Konstanz
 */
public final class ThreadMeter extends AbstractMeter {

    /**
     * the threadgroup to analyse.
     */
    private transient final ThreadGroup topThreadGroup;

    /** Name of the Meter. */
    private static final String NAME = "ThreadMeter";

    /** Unit of the Meter. */
    private static final String UNIT = "threads";

    /** UnitDescription of the Meter. */
    private static final String DESCRIPTION = "Number of Threads";

    /**
     * Constructor;
     */
    public ThreadMeter() {
        super();
        final Thread ownThread = Thread.currentThread();
        final ThreadGroup ownGroup = ownThread.getThreadGroup();
        ThreadGroup group = null;
        do {
            group = ownGroup.getParent();
        } while (group.getParent() != null);
        this.topThreadGroup = group;
    }

    /**
     * Constructor.
     * 
     * @param group
     *            the group of number of threads to analyse.
     */
    public ThreadMeter(final ThreadGroup group) {
        super();
        this.topThreadGroup = group;
    }

    /** {@inheritDoc} */
    @Override
    public String getName() {
        return NAME;
    }

    /** {@inheritDoc} */
    @Override
    public String getUnit() {
        return UNIT;
    }

    /** {@inheritDoc} */
    @Override
    public String getUnitDescription() {
        return DESCRIPTION;
    }

    /** {@inheritDoc} */
    @Override
    public double getValue() {
        return topThreadGroup.activeCount();
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = prime;
        result = prime * result;

        return result;
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(final Object obj) {
        boolean returnVal = true;
        if (this == obj) {
            returnVal = true;
        }
        if (getClass() == obj.getClass()) {
            returnVal = true;
        } else {
            returnVal = false;
        }
        return returnVal;
    }

}