/*
 * [MXComparator.java]
 *
 * Summary: Sort mail MX Strings.
 *
 * Copyright: (c) 2002-2017 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:
 *  1.7 2007-08-21
 */
package com.mindprod.bulk;

import java.util.Comparator;

/**
 * Sort mail MX Strings.
 * <p/>
 * Defines an alternate sort order for String.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.7 2007-08-21 initial release
 * @since 2002
 */
class MXComparator implements Comparator<String>
    {
    /**
     * Sort mailMX Strings, number space String. "5 gmail-smtp-in.l.google.com." "10 alt1.gmail-smtp-in.l.google.com."
     * Defines an alternate sort order for String.
     * Compare two String Objects.
     * Informally, returns (a-b), or +ve if a is more positive than b.
     *
     * @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 )
        {
        // very inefficient, parses on every compare!!!!
        try
            {
            final int space1 = a.indexOf( ' ' );
            final int space2 = b.indexOf( ' ' );
            if ( space1 > 0 && space2 > 0 )
                {
                final int prio1 = Integer.parseInt( a.substring( 0, space1 ) );
                final int prio2 = Integer.parseInt( b.substring( 0, space2 ) );
                if ( prio1 > prio2 )
                    {
                    return -1;
                    }
                if ( prio1 < prio2 )
                    {
                    return 1;
                    }
                // numbers were equal, break tie with strings
                a = a.substring( space1 + 1 );
                b = b.substring( space2 + 1 );
                return a.compareTo( b );
                }
            else
                {
                // were no lead numbers.
                return a.compareTo( b );
                }
            }
        catch ( NumberFormatException e )
            {
            // screwed up numbers, compare alphabetically.
            return a.compareTo( b );
            }
        }
    }