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package org.jooq;

import java.math.BigInteger;
import java.util.Comparator;
import java.util.regex.Pattern;

A comparator that compares file names semantically, just like the Windows
Explorer.

Desired semantic ordering:
version-1
version-2
version-10


Undesired, lexicographic ordering:
version-1
version-10
version-2

Author:
Lukas Eder/**
 * A comparator that compares file names semantically, just like the Windows
 * Explorer.
 * <p>
 * <strong>Desired semantic ordering:</strong>
 *
 * <pre>
 * version-1
 * version-2
 * version-10
 * </pre>
 * <p>
 * <strong>Undesired, lexicographic ordering:</strong>
 *
 * <pre>
 * version-1
 * version-10
 * version-2
 * </pre>
 *
 * @author Lukas Eder
 */
final class FilenameComparator implements Comparator<String> {

    // Idea taken from here: https://codereview.stackexchange.com/a/37217/5314
    private static final Pattern           NUMBERS  = Pattern.compile("(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)");
    public static final FilenameComparator INSTANCE = new FilenameComparator();

    @Override
    public final int compare(String o1, String o2) {
        if (o1 == null || o2 == null)
            return o1 == null ? o2 == null ? 0 : -1 : 1;

        String[] split1 = NUMBERS.split(o1);
        String[] split2 = NUMBERS.split(o2);

        for (int i = 0; i < Math.min(split1.length, split2.length); i++) {
            char c1 = split1[i].charAt(0);
            char c2 = split2[i].charAt(0);
            int cmp = 0;

            if (c1 >= '0' && c1 <= '9' && c2 >= '0' && c2 <= '9')
                cmp = new BigInteger(split1[i]).compareTo(new BigInteger(split2[i]));

            if (cmp == 0)
                cmp = split1[i].compareTo(split2[i]);

            if (cmp != 0)
                return cmp;
        }

        return split1.length - split2.length;
    }
}