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Flying Saucer is a CSS 2.1 renderer written in Java. This artifact provides implementation of the word-break capability using Apache FOP library

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/*
 * Copyright (C) 2017 Lukas Zaruba, [email protected]
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */
package org.xhtmlrenderer.fop.nbsp;

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

/**
 * Processes text and replaces spaces by non-break spaces (\u00A0)
 * on places designated by the language definition file.
 *
 * Language definition files should be located on classpath in the directory
 * "non-break-spaces/${langKey}.nbsp". If lang key contains '_', in first run
 * we search for whole lang key and if not found for part of the lang key before '_'.
 * Encoding of the nbsp file must be utf8.
 *
 * Language definition file consist of line per each rule. Line contains regexp pattern with
 * three groups. Second group will be replaced by \u00A0. First and second will be copied and are used
 * to match the selection properly.
 * Ex.: "([\\s]+and)( )([^\\s]+)" will replace "this and something else" with "this and\u00A0something else"
 * so and will not be left hanging at the end of the line.
 *
 * Rules are applied to the content in the order as they appear in the file and result of one rule run is used
 * as input for the next run.
 *
 * Lines starting with '#' and empty lines are skipped and can be used as comments.
 *
 * @author Lukas Zaruba, [email protected]
 */
public class NonBreakPointsEnhancer {

    private final NonBreakPointsLoader loader;

    public NonBreakPointsEnhancer() {
        this(new NonBreakPointsLoaderImpl());
    }

    NonBreakPointsEnhancer(NonBreakPointsLoader loader) {
        this.loader = loader;
    }

    public String enhance(String input, String lang) {
        if (input == null) return null;
        if (input.isEmpty()) return "";
        if (lang == null || lang.isEmpty()) return input;
        List rules = loader.loadNBSP(lang);
        for (String r : rules) {
            Matcher m = Pattern.compile(r).matcher(input);
            if (m.groupCount() != 3) {
                throw new IllegalArgumentException("Expression must contain exactly 3 groups! " + r);
            }
            if (m.find()) {
                input = m.replaceAll("$1\u00A0$3");
            }
        }
        return input;
    }

}