aboutsummaryrefslogtreecommitdiffstats
path: root/src/main/java/de/pixart/messenger/utils/ImStyleParser.java
blob: 6f65b155265bf873bbbbf06059c10afaa27519d2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
/*
 * Copyright (c) 2017, Daniel Gultsch All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of the copyright holder 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 THE COPYRIGHT HOLDER OR CONTRIBUTORS 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 de.pixart.messenger.utils;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ImStyleParser {
    private final static List<Character> KEYWORDS = Arrays.asList('*', '_', '~', '`');
    private final static List<Character> NO_SUB_PARSING_KEYWORDS = Arrays.asList('`');
    private final static List<Character> BLOCK_KEYWORDS = Arrays.asList('`');
    private final static boolean ALLOW_EMPTY = false;

    public static List<Style> parse(CharSequence text) {
        return parse(text, 0, text.length() - 1);
    }

    private static List<Style> parse(CharSequence text, int start, int end) {
        List<Style> styles = new ArrayList<>();
        for (int i = start; i <= end; ++i) {
            char c = text.charAt(i);
            if (KEYWORDS.contains(c) && precededByWhiteSpace(text, i, start) && !followedByWhitespace(text, i, end)) {
                if (BLOCK_KEYWORDS.contains(c) && isCharRepeatedTwoTimes(text, c, i + 1, end)) {
                    int to = seekEndBlock(text, c, i + 3, end);
                    if (to != -1 && (to != i + 5 || ALLOW_EMPTY)) {
                        String keyword = String.valueOf(c) + String.valueOf(c) + String.valueOf(c);
                        styles.add(new Style(keyword, i, to));
                        i = to;
                        continue;
                    }
                }
                int to = seekEnd(text, c, i + 1, end);
                if (to != -1 && (to != i + 1 || ALLOW_EMPTY)) {
                    styles.add(new Style(c, i, to));
                    if (!NO_SUB_PARSING_KEYWORDS.contains(c)) {
                        styles.addAll(parse(text, i + 1, to - 1));
                    }
                    i = to;
                }
            }
        }
        return styles;
    }

    private static boolean isCharRepeatedTwoTimes(CharSequence text, char c, int index, int end) {
        return index + 1 <= end && text.charAt(index) == c && text.charAt(index) == c;
    }

    private static boolean precededByWhiteSpace(CharSequence text, int index, int start) {
        return index == start || Character.isWhitespace(text.charAt(index - 1));
    }

    private static boolean followedByWhitespace(CharSequence text, int index, int end) {
        return index >= end || Character.isWhitespace(text.charAt(index + 1));
    }

    private static int seekEnd(CharSequence text, char needle, int start, int end) {
        for (int i = start; i <= end; ++i) {
            char c = text.charAt(i);
            if (c == needle && !Character.isWhitespace(text.charAt(i - 1))) {
                return i;
            } else if (c == '\n') {
                return -1;
            }
        }
        return -1;
    }

    private static int seekEndBlock(CharSequence text, char needle, int start, int end) {
        for (int i = start; i <= end; ++i) {
            char c = text.charAt(i);
            if (c == needle && isCharRepeatedTwoTimes(text, needle, i + 1, end)) {
                return i + 2;
            }
        }
        return -1;
    }

    public static class Style {

        private final String keyword;
        private final int start;
        private final int end;

        public Style(char character, int start, int end) {
            this(String.valueOf(character), start, end);
        }

        public Style(String keyword, int start, int end) {
            this.keyword = keyword;
            this.start = start;
            this.end = end;
        }

        public String getKeyword() {
            return keyword;
        }

        public int getStart() {
            return start;
        }

        public int getEnd() {
            return end;
        }
    }
}