/*
 * 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.document;

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.BulkScorer;
import org.apache.lucene.search.CollectionTerminatedException;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Weight;

Adds document suggest capabilities to IndexSearcher. Any CompletionQuery can be used to suggest documents. Use PrefixCompletionQuery for analyzed prefix queries, RegexCompletionQuery for regular expression prefix queries, FuzzyCompletionQuery for analyzed prefix with typo tolerance and ContextQuery to boost and/or filter suggestions by contexts 
@lucene.experimental
/**
 * Adds document suggest capabilities to IndexSearcher.
 * Any {@link CompletionQuery} can be used to suggest documents.
 *
 * Use {@link PrefixCompletionQuery} for analyzed prefix queries,
 * {@link RegexCompletionQuery} for regular expression prefix queries,
 * {@link FuzzyCompletionQuery} for analyzed prefix with typo tolerance
 * and {@link ContextQuery} to boost and/or filter suggestions by contexts
 *
 * @lucene.experimental
 */
public class SuggestIndexSearcher extends IndexSearcher {

  // NOTE: we do not accept an ExecutorService here, because at least the dedup
  // logic in TopSuggestDocsCollector/NRTSuggester would not be thread safe (and maybe other things)

  
Creates a searcher with document suggest capabilities
for reader.
/**
   * Creates a searcher with document suggest capabilities
   * for <code>reader</code>.
   */
  public SuggestIndexSearcher(IndexReader reader) {
    super(reader);
  }

  
Returns top n completion hits for
query
/**
   * Returns top <code>n</code> completion hits for
   * <code>query</code>
   */
  public TopSuggestDocs suggest(CompletionQuery query, int n, boolean skipDuplicates) throws IOException {
    TopSuggestDocsCollector collector = new TopSuggestDocsCollector(n, skipDuplicates);
    suggest(query, collector);
    return collector.get();
  }

  
Lower-level suggest API.
Collects completion hits through collector for query.
TopSuggestDocsCollector.collect(int, CharSequence, CharSequence, float) is called for every matching completion hit. /**
   * Lower-level suggest API.
   * Collects completion hits through <code>collector</code> for <code>query</code>.
   *
   * <p>{@link TopSuggestDocsCollector#collect(int, CharSequence, CharSequence, float)}
   * is called for every matching completion hit.
   */
  public void suggest(CompletionQuery query, TopSuggestDocsCollector collector) throws IOException {
    // TODO use IndexSearcher.rewrite instead
    // have to implement equals() and hashCode() in CompletionQuerys and co
    query = (CompletionQuery) query.rewrite(getIndexReader());
    Weight weight = query.createWeight(this, collector.scoreMode(), 1f);
    for (LeafReaderContext context : getIndexReader().leaves()) {
      BulkScorer scorer = weight.bulkScorer(context);
      if (scorer != null) {
        try {
          scorer.score(collector.getLeafCollector(context), context.reader().getLiveDocs());
        } catch (CollectionTerminatedException e) {
          // collection was terminated prematurely
          // continue with the following leaf
        }
      }
    }
  }
}