package org.apache.lucene.search;

/**
 * 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 java.io.IOException;

import org.apache.lucene.index.Term;
import org.apache.lucene.document.Document;

/** An abstract base class for search implementations.
 * Implements the main search methods.
 * 
 * <p>Note that you can only access Hits from a Searcher as long as it is
 * not yet closed, otherwise an IOException will be thrown. 
 */
public abstract class Searcher implements Searchable {

  /** Returns the documents matching <code>query</code>. 
   * @throws BooleanQuery.TooManyClauses
   */
  public final Hits search(Query query) throws IOException {
    return search(query, (Filter)null);
  }

  /** Returns the documents matching <code>query</code> and
   * <code>filter</code>.
   * @throws BooleanQuery.TooManyClauses
   */
  public Hits search(Query query, Filter filter) throws IOException {
    return new Hits(this, query, filter);
  }

  /** Returns documents matching <code>query</code> sorted by
   * <code>sort</code>.
   * @throws BooleanQuery.TooManyClauses
   */
  public Hits search(Query query, Sort sort)
    throws IOException {
    return new Hits(this, query, null, sort);
  }

  /** Returns documents matching <code>query</code> and <code>filter</code>,
   * sorted by <code>sort</code>.
   * @throws BooleanQuery.TooManyClauses
   */
  public Hits search(Query query, Filter filter, Sort sort)
    throws IOException {
    return new Hits(this, query, filter, sort);
  }

  /** Expert: Low-level search implementation with arbitrary sorting.  Finds
   * the top <code>n</code> hits for <code>query</code>, applying
   * <code>filter</code> if non-null, and sorting the hits by the criteria in
   * <code>sort</code>.
   *
   * <p>Applications should usually call {@link
   * Searcher#search(Query,Filter,Sort)} instead.
   * @throws BooleanQuery.TooManyClauses
   */
  public TopFieldDocs search(Query query, Filter filter, int n,
                             Sort sort) throws IOException {
    return search(createWeight(query), filter, n, sort);
  }

  /** Lower-level search API.
   *
   * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
   * scoring document.
   *
   * <p>Applications should only use this if they need <i>all</i> of the
   * matching documents.  The high-level search API ({@link
   * Searcher#search(Query)}) is usually more efficient, as it skips
   * non-high-scoring hits.
   * <p>Note: The <code>score</code> passed to this method is a raw score.
   * In other words, the score will not necessarily be a float whose value is
   * between 0 and 1.
   * @throws BooleanQuery.TooManyClauses
   */
  public void search(Query query, HitCollector results)
    throws IOException {
    search(query, (Filter)null, results);
  }

  /** Lower-level search API.
   *
   * <p>{@link HitCollector#collect(int,float)} is called for every non-zero
   * scoring document.
   * <br>HitCollector-based access to remote indexes is discouraged.
   *
   * <p>Applications should only use this if they need <i>all</i> of the
   * matching documents.  The high-level search API ({@link
   * Searcher#search(Query)}) is usually more efficient, as it skips
   * non-high-scoring hits.
   *
   * @param query to match documents
   * @param filter if non-null, a bitset used to eliminate some documents
   * @param results to receive hits
   * @throws BooleanQuery.TooManyClauses
   */
  public void search(Query query, Filter filter, HitCollector results)
    throws IOException {
    search(createWeight(query), filter, results);
  }

  /** Expert: Low-level search implementation.  Finds the top <code>n</code>
   * hits for <code>query</code>, applying <code>filter</code> if non-null.
   *
   * <p>Called by {@link Hits}.
   *
   * <p>Applications should usually call {@link Searcher#search(Query)} or
   * {@link Searcher#search(Query,Filter)} instead.
   * @throws BooleanQuery.TooManyClauses
   */
  public TopDocs search(Query query, Filter filter, int n)
    throws IOException {
    return search(createWeight(query), filter, n);
  }

  /** Returns an Explanation that describes how <code>doc</code> scored against
   * <code>query</code>.
   *
   * <p>This is intended to be used in developing Similarity implementations,
   * and, for good performance, should not be displayed with every hit.
   * Computing an explanation is as expensive as executing the query over the
   * entire index.
   */
  public Explanation explain(Query query, int doc) throws IOException {
    return explain(createWeight(query), doc);
  }

  /** The Similarity implementation used by this searcher. */
  private Similarity similarity = Similarity.getDefault();

  /** Expert: Set the Similarity implementation used by this Searcher.
   *
   * @see Similarity#setDefault(Similarity)
   */
  public void setSimilarity(Similarity similarity) {
    this.similarity = similarity;
  }

  /** Expert: Return the Similarity implementation used by this Searcher.
   *
   * <p>This defaults to the current value of {@link Similarity#getDefault()}.
   */
  public Similarity getSimilarity() {
    return this.similarity;
  }

  /**
   * creates a weight for <code>query</code>
   * @return new weight
   */
  protected Weight createWeight(Query query) throws IOException {
      return query.weight(this);
  }

  // inherit javadoc
  public int[] docFreqs(Term[] terms) throws IOException {
    int[] result = new int[terms.length];
    for (int i = 0; i < terms.length; i++) {
      result[i] = docFreq(terms[i]);
    }
    return result;
  }

  /* The following abstract methods were added as a workaround for GCJ bug #15411.
   * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15411
   */
  abstract public void search(Weight weight, Filter filter, HitCollector results) throws IOException;
  abstract public void close() throws IOException;
  abstract public int docFreq(Term term) throws IOException;
  abstract public int maxDoc() throws IOException;
  abstract public TopDocs search(Weight weight, Filter filter, int n) throws IOException;
  abstract public Document doc(int i) throws IOException;
  abstract public Query rewrite(Query query) throws IOException;
  abstract public Explanation explain(Weight weight, int doc) throws IOException;
  abstract public TopFieldDocs search(Weight weight, Filter filter, int n, Sort sort) throws IOException;
  /* End patch for GCJ bug #15411. */
}