1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.email.mail.internet;
18
19import java.util.regex.Matcher;
20import java.util.regex.Pattern;
21
22public class EmailHtmlUtil {
23
24    // Regex that matches characters that have special meaning in HTML. '<', '>', '&' and
25    // multiple continuous spaces.
26    private static final Pattern PLAIN_TEXT_TO_ESCAPE = Pattern.compile("[<>&]| {2,}|\r?\n");
27
28    /**
29     * Escape some special character as HTML escape sequence.
30     *
31     * @param text Text to be displayed using WebView.
32     * @return Text correctly escaped.
33     */
34    public static String escapeCharacterToDisplay(String text) {
35        Pattern pattern = PLAIN_TEXT_TO_ESCAPE;
36        Matcher match = pattern.matcher(text);
37
38        if (match.find()) {
39            StringBuilder out = new StringBuilder();
40            int end = 0;
41            do {
42                int start = match.start();
43                out.append(text.substring(end, start));
44                end = match.end();
45                int c = text.codePointAt(start);
46                if (c == ' ') {
47                    // Escape successive spaces into series of "&nbsp;".
48                    for (int i = 1, n = end - start; i < n; ++i) {
49                        out.append("&nbsp;");
50                    }
51                    out.append(' ');
52                } else if (c == '\r' || c == '\n') {
53                    out.append("<br>");
54                } else if (c == '<') {
55                    out.append("&lt;");
56                } else if (c == '>') {
57                    out.append("&gt;");
58                } else if (c == '&') {
59                    out.append("&amp;");
60                }
61            } while (match.find());
62            out.append(text.substring(end));
63            text = out.toString();
64        }
65        return text;
66    }
67}
68