code: /* LanguageTool, a natural language style checker
   * Copyright (C) 2016 Jaume Ortolà
   *
   * 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 org.languagetool.Language;
  import org.languagetool.Premium;
  import org.languagetool.Tag;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /* 
   * Remove overlapping errors according to the priorities established for the language.  
   * (It assumes the input list is ordered by start position)
   * 
   * @since 3.6
   */
  public class CleanOverlappingFilter implements RuleMatchFilter {
  
    private static final int negativeConstant = Integer.MIN_VALUE + 10000;
  
    private final Language language;
    private final boolean hidePremiumMatches;
  
    public CleanOverlappingFilter(Language lang, boolean hidePremiumMatches) {
      this.language = lang;
      this.hidePremiumMatches = hidePremiumMatches;
    }
    
    @Override
    public final List<RuleMatch> filter(List<RuleMatch> ruleMatches) {
      List<RuleMatch> cleanList = new ArrayList<>();
      RuleMatch prevRuleMatch = null;
      for (RuleMatch ruleMatch: ruleMatches) {
        if (prevRuleMatch == null) {  // first item
          prevRuleMatch = ruleMatch;
          continue;
        }
        if (ruleMatch.getFromPos() < prevRuleMatch.getFromPos()) {
          throw new IllegalArgumentException(
              "The list of rule matches is not ordered. Make sure it is sorted by start position.");
        }
        // juxtaposed errors adding a comma in the same place
        boolean isJuxtaposedComma = false;
        if (ruleMatch.getFromPos() == prevRuleMatch.getToPos()
            && ruleMatch.getSuggestedReplacements().size() > 0
            && prevRuleMatch.getSuggestedReplacements().size() > 0) {
          String suggestion = ruleMatch.getSuggestedReplacements().get(0);
          String prevSuggestion = prevRuleMatch.getSuggestedReplacements().get(0);
          if (prevSuggestion.endsWith(",") && suggestion.startsWith(", ")) {
            isJuxtaposedComma = true;
          }
        }
        // no overlapping (juxtaposed errors are not removed)
        if (ruleMatch.getFromPos() >= prevRuleMatch.getToPos() && !isJuxtaposedComma) {
          cleanList.add(prevRuleMatch);
          prevRuleMatch = ruleMatch;
          continue;
        }
        // overlapping
        int currentPriority = language.getRulePriority(ruleMatch.getRule());
        if (isPremiumRule(ruleMatch) && hidePremiumMatches) {
          // non-premium match should win, so the premium match does *not* become a hidden match
          // (we'd show hidden matches for errors covered by an Open Source match)
          currentPriority = Integer.MIN_VALUE;
        }
        if (ruleMatch.getRule().getTags().contains(Tag.picky) && currentPriority != Integer.MIN_VALUE) {
          currentPriority += negativeConstant;
        }
        int prevPriority = language.getRulePriority(prevRuleMatch.getRule());
        if (isPremiumRule(prevRuleMatch) && hidePremiumMatches) {
          prevPriority = Integer.MIN_VALUE;
        }
        if (prevRuleMatch.getRule().getTags().contains(Tag.picky) && prevPriority != Integer.MIN_VALUE) {
          prevPriority += negativeConstant;
        }
        if (currentPriority == prevPriority) {
          // take the longest error:
          currentPriority = ruleMatch.getToPos() - ruleMatch.getFromPos();
          prevPriority = prevRuleMatch.getToPos() - prevRuleMatch.getFromPos();
        }
        if (currentPriority == prevPriority) {
          currentPriority++; // take the last one (to keep the current results in the web UI) 
        }
        if (currentPriority > prevPriority) {
          prevRuleMatch = ruleMatch;
        }
      }
      //last match
      if (prevRuleMatch != null) {
        cleanList.add(prevRuleMatch);
      }
      return cleanList;
    }
  
    protected boolean isPremiumRule(RuleMatch ruleMatch) {
      return Premium.get().isPremiumRule(ruleMatch.getRule());
    }
  
  }
  