code: /* LanguageTool, a natural language style checker
   * Copyright (C) 2014 Daniel Naber (http://danielnaber.de/)
   *
   * This library 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 library 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 library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
   * USA
   */
  package org.languagetool.rules;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.ResourceBundle;
  import org.languagetool.AnalyzedSentence;
  import org.languagetool.AnalyzedTokenReadings;
  import org.languagetool.Language;
  import org.languagetool.tools.Tools;
  
  /**
   * A rule that checks for empty lines. Useful especially for office extension
   * It checks only linebreaks because empty paragraphs can't be handled in LO/OO 
   * 
   * @author Fred Kruse
   */
  
  public class EmptyLineRule extends TextLevelRule {
  
    private final Language lang;
    
    public EmptyLineRule(ResourceBundle messages, Language lang, boolean defaultActive) {
      super(messages);
      super.setCategory(Categories.STYLE.getCategory(messages));
      this.lang = lang;
      if (!defaultActive) {
        setDefaultOff();
      }
      setOfficeDefaultOn();  // Default for LO/OO is always On
      setLocQualityIssueType(ITSIssueType.Style);
    }
  
    public EmptyLineRule(ResourceBundle messages, Language lang) {
      this(messages, lang, false);
    }
  
    @Override
    public String getId() {
      return "EMPTY_LINE";
    }
  
    @Override
    public String getDescription() {
      return messages.getString("empty_line_rule_desc");
    }
  
    @Override
    public org.languagetool.rules.RuleMatch[] match(List<AnalyzedSentence> sentences) throws IOException {
      List<RuleMatch> ruleMatches = new ArrayList<>();
      int pos = 0;
      for (int n = 0; n < sentences.size() - 1; n++) {
        AnalyzedSentence sentence = sentences.get(n);
        if(Tools.isParagraphEnd(sentences, n, lang)) {
          if(isSecondParagraphEndMark(sentence.getText())) {
            AnalyzedTokenReadings[] tokens = sentence.getTokensWithoutWhitespace();
            if(tokens.length > 1) {
              int fromPos = pos + tokens[tokens.length - 1].getStartPos();
              int toPos = pos + tokens[tokens.length - 1].getEndPos();
              RuleMatch ruleMatch = new RuleMatch(this, sentence, fromPos, toPos, messages.getString("empty_line_rule_msg"));
              // Can't use SuggestedReplacement because of problems in LO/OO dialog with linebreaks
              ruleMatches.add(ruleMatch);
            }
          }
        }
        pos += sentence.getCorrectedTextLength();
      }
      return toRuleMatchArray(ruleMatches);
    }
  
    private boolean isSecondParagraphEndMark(String sentence) {
      if (lang.getSentenceTokenizer().singleLineBreaksMarksPara()) {
        if (sentence.endsWith("\n\n") || sentence.endsWith("\n\r\n\r")) {
          return true;
        }
      } else { 
        if (sentence.endsWith("\n\n\n\n") || sentence.endsWith("\n\r\n\r\n\r\n\r") || sentence.endsWith("\r\n\r\n\r\n\r\n")) {
          return true;
        }
      }
      return false;
    }
    
    @Override
    public int minToCheckParagraph() {
      return 1;
    }
  
  }
  