/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.lucene.search.suggest.analyzing;

import java.io.IOException;
import java.util.Map;

import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.analysis.en.EnglishAnalyzer;
import org.apache.lucene.analysis.util.ResourceLoader;
import org.apache.lucene.analysis.util.ResourceLoaderAware;
import org.apache.lucene.analysis.util.TokenFilterFactory;

Factory for SuggestStopFilter. 
<fieldType name="autosuggest" class="solr.TextField" 
           positionIncrementGap="100" autoGeneratePhraseQueries="true">
  <analyzer>
    <tokenizer class="solr.WhitespaceTokenizerFactory"/>
    <filter class="solr.LowerCaseFilterFactory"/>
    <filter class="solr.SuggestStopFilterFactory" ignoreCase="true"
            words="stopwords.txt" format="wordset"/>
  </analyzer>
</fieldType>

All attributes are optional:


 
ignoreCase defaults to false
 
words should be the name of a stopwords file to parse, if not specified the factory will use EnglishAnalyzer.ENGLISH_STOP_WORDS_SET 
 
format defines how the words file will be parsed, 
     and defaults to wordset.  If words is not specified, 
     then format must not be specified.
 


The valid values for the format option are:


 
wordset - This is the default format, which supports one word per line (including any intra-word whitespace) and allows whole line comments beginning with the "#" character. Blank lines are ignored. See WordlistLoader.getLines for details. 
 
snowball - This format allows for multiple words specified on each line, and trailing comments may be specified using the vertical line ("|"). Blank lines are ignored. See WordlistLoader.getSnowballWordSet for details. 

Since:
5.0.0/**
 * Factory for {@link SuggestStopFilter}.
 *
 * <pre class="prettyprint">
 * &lt;fieldType name="autosuggest" class="solr.TextField" 
 *            positionIncrementGap="100" autoGeneratePhraseQueries="true"&gt;
 *   &lt;analyzer&gt;
 *     &lt;tokenizer class="solr.WhitespaceTokenizerFactory"/&gt;
 *     &lt;filter class="solr.LowerCaseFilterFactory"/&gt;
 *     &lt;filter class="solr.SuggestStopFilterFactory" ignoreCase="true"
 *             words="stopwords.txt" format="wordset"/&gt;
 *   &lt;/analyzer&gt;
 * &lt;/fieldType&gt;</pre>
 *
 * <p>
 * All attributes are optional:
 * </p>
 * <ul>
 *  <li><code>ignoreCase</code> defaults to <code>false</code></li>
 *  <li><code>words</code> should be the name of a stopwords file to parse, if not 
 *      specified the factory will use {@link EnglishAnalyzer#ENGLISH_STOP_WORDS_SET}
 *  </li>
 *  <li><code>format</code> defines how the <code>words</code> file will be parsed, 
 *      and defaults to <code>wordset</code>.  If <code>words</code> is not specified, 
 *      then <code>format</code> must not be specified.
 *  </li>
 * </ul>
 * <p>
 * The valid values for the <code>format</code> option are:
 * </p>
 * <ul>
 *  <li><code>wordset</code> - This is the default format, which supports one word per 
 *      line (including any intra-word whitespace) and allows whole line comments 
 *      beginning with the "#" character.  Blank lines are ignored.  See 
 *      {@link WordlistLoader#getLines WordlistLoader.getLines} for details.
 *  </li>
 *  <li><code>snowball</code> - This format allows for multiple words specified on each 
 *      line, and trailing comments may be specified using the vertical line ("&#124;"). 
 *      Blank lines are ignored.  See 
 *      {@link WordlistLoader#getSnowballWordSet WordlistLoader.getSnowballWordSet}
 *      for details.
 *  </li>
 * </ul>
 * @since 5.0.0
 */
  public class SuggestStopFilterFactory extends TokenFilterFactory implements ResourceLoaderAware {
  
the default format, one word per line, whole line comments start with "#" /** the default format, one word per line, whole line comments start with "#" */
  public static final String FORMAT_WORDSET = "wordset";
  
multiple words may be specified on each line, trailing comments start with "|" /** multiple words may be specified on each line, trailing comments start with "&#124;" */
  public static final String FORMAT_SNOWBALL = "snowball";

  private CharArraySet stopWords;
  private final String stopWordFiles;
  private final String format;
  private final boolean ignoreCase;

  
Creates a new StopFilterFactory /** Creates a new StopFilterFactory */
  public SuggestStopFilterFactory(Map<String,String> args) {
    super(args);
    stopWordFiles = get(args, "words");
    format = get(args, "format", (null == stopWordFiles ? null : FORMAT_WORDSET));
    ignoreCase = getBoolean(args, "ignoreCase", false);
    if (!args.isEmpty()) {
      throw new IllegalArgumentException("Unknown parameters: " + args);
    }
  }

  @Override
  public void inform(ResourceLoader loader) throws IOException {
    if (stopWordFiles != null) {
      if (FORMAT_WORDSET.equalsIgnoreCase(format)) {
        stopWords = getWordSet(loader, stopWordFiles, ignoreCase);
      } else if (FORMAT_SNOWBALL.equalsIgnoreCase(format)) {
        stopWords = getSnowballWordSet(loader, stopWordFiles, ignoreCase);
      } else {
        throw new IllegalArgumentException("Unknown 'format' specified for 'words' file: " + format);
      }
    } else {
      if (null != format) {
        throw new IllegalArgumentException("'format' can not be specified w/o an explicit 'words' file: " + format);
      }
      stopWords = new CharArraySet(EnglishAnalyzer.ENGLISH_STOP_WORDS_SET, ignoreCase);
    }
  }

  
Whether or not to ignore case /** Whether or not to ignore case */
  public boolean isIgnoreCase() {
    return ignoreCase;
  }

  
Returns the configured stopword set /** Returns the configured stopword set */
  public CharArraySet getStopWords() {
    return stopWords;
  }

  @Override
  public TokenStream create(TokenStream input) {
    SuggestStopFilter suggestStopFilter = new SuggestStopFilter(input, stopWords);
    return suggestStopFilter;
  }
}