001// License: GPL. For details, see LICENSE file.
002package org.openstreetmap.josm.tools;
003
004/*
005 * The Alphanum Algorithm is an improved sorting algorithm for strings
006 * containing numbers. Instead of sorting numbers in ASCII order like a standard
007 * sort, this algorithm sorts numbers in numeric order.
008 *
009 * The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
010 *
011 * Released under the MIT License - https://opensource.org/licenses/MIT
012 *
013 * Copyright 2007-2017 David Koelle
014 *
015 * Permission is hereby granted, free of charge, to any person obtaining
016 * a copy of this software and associated documentation files (the "Software"),
017 * to deal in the Software without restriction, including without limitation
018 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
019 * and/or sell copies of the Software, and to permit persons to whom the
020 * Software is furnished to do so, subject to the following conditions:
021 *
022 * The above copyright notice and this permission notice shall be included
023 * in all copies or substantial portions of the Software.
024 *
025 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
026 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
027 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
028 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
029 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
030 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
031 * USE OR OTHER DEALINGS IN THE SOFTWARE.
032 */
033import java.io.Serializable;
034import java.text.Collator;
035import java.util.Comparator;
036
037/**
038 * The Alphanum Algorithm is an improved sorting algorithm for strings
039 * containing numbers: Instead of sorting numbers in ASCII order like a standard
040 * sort, this algorithm sorts numbers in numeric order.
041 *
042 * The Alphanum Algorithm is discussed at http://www.DaveKoelle.com
043 *
044 * This is an updated version with enhancements made by Daniel Migowski, Andre
045 * Bogus, David Koelle and others.
046 *
047 */
048public final class AlphanumComparator implements Comparator<String>, Serializable {
049
050    private static final long serialVersionUID = 1L;
051
052    private static final AlphanumComparator INSTANCE = new AlphanumComparator();
053
054    /**
055     * Replies the unique instance.
056     * @return the unique instance
057     */
058    public static AlphanumComparator getInstance() {
059        return INSTANCE;
060    }
061
062    /**
063     * Constructs a new Alphanum Comparator.
064     */
065    private AlphanumComparator() {
066    }
067
068    /**
069     * Returns an alphanum chunk.
070     * Length of string is passed in for improved efficiency (only need to calculate it once).
071     * @param s string
072     * @param slength string length
073     * @param marker position
074     * @return alphanum chunk found at given position
075     */
076    private static String getChunk(String s, int slength, int marker) {
077        StringBuilder chunk = new StringBuilder();
078        char c = s.charAt(marker);
079        chunk.append(c);
080        marker++;
081        if (Character.isDigit(c)) {
082            while (marker < slength) {
083                c = s.charAt(marker);
084                if (!Character.isDigit(c)) {
085                    break;
086                }
087                chunk.append(c);
088                marker++;
089            }
090        } else {
091            while (marker < slength) {
092                c = s.charAt(marker);
093                if (Character.isDigit(c)) {
094                    break;
095                }
096                chunk.append(c);
097                marker++;
098            }
099        }
100        return chunk.toString();
101    }
102
103    @Override
104    public int compare(String s1, String s2) {
105        if (s1 == null && s2 == null) {
106            return 0;
107        } else if (s1 == null) {
108            return -1;
109        } else if (s2 == null) {
110            return 1;
111        }
112
113        int thisMarker = 0;
114        int thatMarker = 0;
115        int s1Length = s1.length();
116        int s2Length = s2.length();
117
118        while (thisMarker < s1Length && thatMarker < s2Length) {
119            String thisChunk = getChunk(s1, s1Length, thisMarker);
120            thisMarker += thisChunk.length();
121
122            String thatChunk = getChunk(s2, s2Length, thatMarker);
123            thatMarker += thatChunk.length();
124
125            // If both chunks contain numeric characters, sort them numerically
126            int result;
127            if (Character.isDigit(thisChunk.charAt(0)) && Character.isDigit(thatChunk.charAt(0))) {
128                // Simple chunk comparison by length.
129                int thisChunkLength = thisChunk.length();
130                result = thisChunkLength - thatChunk.length();
131                // If equal, the first different number counts
132                if (result == 0) {
133                    for (int i = 0; i < thisChunkLength; i++) {
134                        result = thisChunk.charAt(i) - thatChunk.charAt(i);
135                        if (result != 0) {
136                            return result;
137                        }
138                    }
139                }
140            } else {
141                // Instantiate the collator
142                Collator compareOperator = Collator.getInstance();
143                // Compare regardless of accented letters
144                compareOperator.setStrength(Collator.SECONDARY);
145                result = compareOperator.compare(thisChunk, thatChunk);
146            }
147
148            if (result != 0) {
149                return result;
150            }
151        }
152
153        return s1Length - s2Length;
154    }
155}