package org.apache.lucene.analysis.shingle;

/*
 * 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.
 */

import org.apache.lucene.analysis.shingle.ShingleFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.util.TokenFilterFactory;

import java.util.Map;

/** 
 * Factory for {@link ShingleFilter}.
 * <pre class="prettyprint" >
 * <fieldType name="text_shingle" class="solr.TextField" positionIncrementGap="100">
 *   <analyzer>
 *     <tokenizer class="solr.WhitespaceTokenizerFactory"/>
 *     <filter class="solr.ShingleFilterFactory" minShingleSize="2" maxShingleSize="2"
 *             outputUnigrams="true" outputUnigramsIfNoShingles="false" tokenSeparator=" "/>
 *   </analyzer>
 * </fieldType></pre>
 *
 */
public class ShingleFilterFactory extends TokenFilterFactory {
  private int minShingleSize;
  private int maxShingleSize;
  private boolean outputUnigrams;
  private boolean outputUnigramsIfNoShingles;
  private String tokenSeparator;

  @Override
  public void init(Map<String, String> args) {
    super.init(args);
    maxShingleSize = getInt("maxShingleSize", 
                            ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
    if (maxShingleSize < 2) {
      throw new IllegalArgumentException("Invalid maxShingleSize (" + maxShingleSize
                              + ") - must be at least 2");
    }
    minShingleSize = getInt("minShingleSize",
                            ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE);
    if (minShingleSize < 2) {
      throw new IllegalArgumentException("Invalid minShingleSize (" + minShingleSize
                              + ") - must be at least 2");
    }
    if (minShingleSize > maxShingleSize) {
      throw new IllegalArgumentException("Invalid minShingleSize (" + minShingleSize
                              + ") - must be no greater than maxShingleSize ("
                              + maxShingleSize + ")");
    }
    outputUnigrams = getBoolean("outputUnigrams", true);
    outputUnigramsIfNoShingles = getBoolean("outputUnigramsIfNoShingles", false);
    tokenSeparator = args.containsKey("tokenSeparator")
                     ? args.get("tokenSeparator")
                     : ShingleFilter.TOKEN_SEPARATOR;
  }
  public ShingleFilter create(TokenStream input) {
    ShingleFilter r = new ShingleFilter(input, minShingleSize, maxShingleSize);
    r.setOutputUnigrams(outputUnigrams);
    r.setOutputUnigramsIfNoShingles(outputUnigramsIfNoShingles);
    r.setTokenSeparator(tokenSeparator);
    return r;
  }
}