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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.jscsi.utils;

/**
 * SerialArithmeticNumber
 * 
 * This class encapsulate the behavior of how to compare and increment a number in Serial Number Arithmetic, which is
 * defined in [RFC1982].
 * 
 * @author Volker Wildi, University of Konstanz
 */
public final class SerialArithmeticNumber implements Comparable {

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------

    /**
     * This is the wrap around divisor (2**32) of the modulo operation used by incrementing the sequence numbers. See
     * [RFC1982] for details.
     */
    private static final long MAXIMUM_VALUE = 0xFFFFFFFFL;

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------

    /** The current value. */
    private long serialNumber;

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------

    /**
     * Default constructor to create a new, empty SerialArithmeticNumber instance, which is initialized to
     * 0.
     */
    public SerialArithmeticNumber () {

    }

    /**
     * Constructor to create a new SerialArithmeticNumber instance, which is initialized to
     * startValue.
     * 
     * @param startValue The start value.
     */
    public SerialArithmeticNumber (final int startValue) {

        if (startValue < 0 || startValue > MAXIMUM_VALUE) { throw new IllegalArgumentException(startValue + " is out of range."); }

        serialNumber = startValue;
    }

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------

    /**
     * Same as the compareTo method only with the exception of another parameter type.
     * 
     * @param anotherSerialNumber The number to compare with.
     * @return a negative integer, zero, or a positive integer as this SerialArithmeticNumber is less than,
     *         equal to, or greater than the given number.
     */
    public final int compareTo (final int anotherSerialNumber) {

        return compareTo(new Integer(anotherSerialNumber));
    }

    /** {@inheritDoc} */
    public final synchronized int compareTo (final Integer anotherSerialNumber) {

        long diff = serialNumber - Utils.getUnsignedLong(anotherSerialNumber.intValue());
        if (diff >= MAXIMUM_VALUE) {
            diff -= (MAXIMUM_VALUE + 1);
        } else if (diff < -MAXIMUM_VALUE) {
            diff += (MAXIMUM_VALUE + 1);
        }
        return (int) diff;
    }

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------

    /**
     * Returns the current value of this SerialArithmeticNumber instance.
     * 
     * @return The current value of this SerialArithmeticNumber instance.
     */
    public final synchronized int getValue () {

        return (int) serialNumber;
    }

    /**
     * Increments the value of this SerialArithmeticNumber instance.
     */
    public final synchronized void increment () {

        if (serialNumber == MAXIMUM_VALUE) {
            serialNumber = 0;
        } else {
            serialNumber++;
        }
    }

    /**
     * Updates the value of this SerialArithmeticNumber instance to the given one.
     * 
     * @param newValue The new value.
     */
    public final synchronized void setValue (final int newValue) {

        if (newValue < 0 || newValue > MAXIMUM_VALUE) { throw new IllegalArgumentException(newValue + " is out of range."); }

        serialNumber = newValue;
    }

    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------
    // --------------------------------------------------------------------------
}