/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.email.mail.internet;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class EmailHtmlUtil {

    // Regex that matches characters that have special meaning in HTML. '<', '>', '&' and
    // multiple continuous spaces.
    private static final Pattern PLAIN_TEXT_TO_ESCAPE = Pattern.compile("[<>&]| {2,}|\r?\n");

    /**
     * Escape some special character as HTML escape sequence.
     * 
     * @param text Text to be displayed using WebView.
     * @return Text correctly escaped.
     */
    public static String escapeCharacterToDisplay(String text) {
        Pattern pattern = PLAIN_TEXT_TO_ESCAPE;
        Matcher match = pattern.matcher(text);
        
        if (match.find()) {
            StringBuilder out = new StringBuilder();
            int end = 0;
            do {
                int start = match.start();
                out.append(text.substring(end, start));
                end = match.end();
                int c = text.codePointAt(start);
                if (c == ' ') {
                    // Escape successive spaces into series of " ".
                    for (int i = 1, n = end - start; i < n; ++i) {
                        out.append(" ");
                    }
                    out.append(' ');
                } else if (c == '\r' || c == '\n') {
                    out.append("<br>");
                } else if (c == '<') {
                    out.append("<");
                } else if (c == '>') {
                    out.append(">");
                } else if (c == '&') {
                    out.append("&");
                }
            } while (match.find());
            out.append(text.substring(end));
            text = out.toString();
        }        
        return text;
    }
}