/*
 * [Shuffle.java]
 *
 * Summary: Shuffle items into a different random order each time it is run.
 *
 * Copyright: (c) 2014-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  1.0 2014-05-01 initial version
 */
package com.mindprod.sortcode;

import com.mindprod.common18.FNV1a64;

import java.util.Comparator;
import java.util.Random;

/**
 * Shuffle items into a different random order each time it is run.
 * <p/>
 * compare two blocks of text to sort them into a different random order each time this is run.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.0 2014-05-01 initial version
 * @since 2014-05-01
 */
public class Shuffle implements Comparator<String>
    {
    /**
     * randomiser that stays constant through one sort
     */
    private static final long SEED = new Random().nextLong();

    private static long computeKey( String s )
        {
        // this ensures Shuffle is consistent within each run of the desired final order.
        // we don't want to drive Collections.sort mad by changing keys in the middle of a sort.
        return FNV1a64.computeHash( s ) ^ SEED;
        } // /method

    /**
     * Compare two Strings
     *
     * @param a first String to compare
     * @param b second String to compare
     *
     * @return +ve if a&gt;b, 0 if a==b, -ve if a&lt;b
     */
    public final int compare( String a, String b )
        {
        return Long.compare( computeKey( a ), computeKey( b ) );
        } // /methods
    } // end class