1/*
2 * Copyright (c) 2017, Daniel Gultsch All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without modification,
5 * are permitted provided that the following conditions are met:
6 *
7 * 1. Redistributions of source code must retain the above copyright notice, this
8 * list of conditions and the following disclaimer.
9 *
10 * 2. Redistributions in binary form must reproduce the above copyright notice,
11 * this list of conditions and the following disclaimer in the documentation and/or
12 * other materials provided with the distribution.
13 *
14 * 3. Neither the name of the copyright holder nor the names of its contributors
15 * may be used to endorse or promote products derived from this software without
16 * specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
22 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
25 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30package eu.siacs.conversations.utils;
31
32import java.util.ArrayList;
33import java.util.Arrays;
34import java.util.List;
35
36public class ImStyleParser {
37
38 private final static List<Character> KEYWORDS = Arrays.asList('*', '_', '~', '`');
39 private final static List<Character> NO_SUB_PARSING_KEYWORDS = Arrays.asList('`');
40 private final static List<Character> BLOCK_KEYWORDS = Arrays.asList('`');
41 private final static boolean ALLOW_EMPTY = false;
42
43 public static List<Style> parse(CharSequence text) {
44 return parse(text, 0, text.length() - 1);
45 }
46
47 public static List<Style> parse(CharSequence text, int start, int end) {
48 List<Style> styles = new ArrayList<>();
49 for (int i = start; i <= end; ++i) {
50 char c = text.charAt(i);
51 if (KEYWORDS.contains(c) && precededByWhiteSpace(text, i, start) && !followedByWhitespace(text, i, end)) {
52 if (BLOCK_KEYWORDS.contains(c) && isCharRepeatedTwoTimes(text, c, i + 1, end)) {
53 int to = seekEndBlock(text, c, i + 3, end);
54 if (to != -1 && (to != i + 5 || ALLOW_EMPTY)) {
55 String keyword = String.valueOf(c) + String.valueOf(c) + String.valueOf(c);
56 styles.add(new Style(keyword, i, to));
57 i = to;
58 continue;
59 }
60 }
61 int to = seekEnd(text, c, i + 1, end);
62 if (to != -1 && (to != i + 1 || ALLOW_EMPTY)) {
63 styles.add(new Style(c, i, to));
64 if (!NO_SUB_PARSING_KEYWORDS.contains(c)) {
65 styles.addAll(parse(text, i + 1, to - 1));
66 }
67 i = to;
68 }
69 }
70 }
71 return styles;
72 }
73
74 private static boolean isCharRepeatedTwoTimes(CharSequence text, char c, int index, int end) {
75 return index + 1 <= end && text.charAt(index) == c && text.charAt(index+1) == c;
76 }
77
78 private static boolean precededByWhiteSpace(CharSequence text, int index, int start) {
79 return index == start || Character.isWhitespace(text.charAt(index - 1));
80 }
81
82 private static boolean followedByWhitespace(CharSequence text, int index, int end) {
83 return index >= end || Character.isWhitespace(text.charAt(index + 1));
84 }
85
86 private static int seekEnd(CharSequence text, char needle, int start, int end) {
87 for (int i = start; i <= end; ++i) {
88 char c = text.charAt(i);
89 if (c == needle && !Character.isWhitespace(text.charAt(i - 1))) {
90 return i;
91 } else if (c == '\n') {
92 return -1;
93 }
94 }
95 return -1;
96 }
97
98 private static int seekEndBlock(CharSequence text, char needle, int start, int end) {
99 for (int i = start; i <= end; ++i) {
100 char c = text.charAt(i);
101 if (c == needle && isCharRepeatedTwoTimes(text, needle, i + 1, end)) {
102 return i + 2;
103 }
104 }
105 return -1;
106 }
107
108 public static class Style {
109
110 private final String keyword;
111 private final int start;
112 private final int end;
113
114 public Style(char character, int start, int end) {
115 this(String.valueOf(character), start, end);
116 }
117
118 public Style(String keyword, int start, int end) {
119 this.keyword = keyword;
120 this.start = start;
121 this.end = end;
122 }
123
124 public String getKeyword() {
125 return keyword;
126 }
127
128 public int getStart() {
129 return start;
130 }
131
132 public int getEnd() {
133 return end;
134 }
135 }
136}