content: 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 org.apache.lucene.util.PriorityQueue;
  import java.io.IOException;
  import java.text.Collator;
  import java.util.Locale;
  
  /**
   * Expert: Collects sorted results from Searchable's and collates them.
   * The elements put into this queue must be of type FieldDoc.
   *
   * <p>Created: Feb 11, 2004 2:04:21 PM
   *
   * @since   lucene 1.4
   */
  class FieldDocSortedHitQueue extends PriorityQueue<FieldDoc> {
  
    volatile SortField[] fields = null;
  
    // used in the case where the fields are sorted by locale
    // based strings
    volatile Collator[] collators = null;
  
    volatile FieldComparator[] comparators = null;
  
  
    /**
     * Creates a hit queue sorted by the given list of fields.
     * @param fields Fieldable names, in priority order (highest priority first).
     * @param size  The number of hits to retain.  Must be greater than zero.
     */
    FieldDocSortedHitQueue (int size) {
      initialize (size);
    }
  
  
    /**
     * Allows redefinition of sort fields if they are <code>null</code>.
     * This is to handle the case using ParallelMultiSearcher where the
     * original list contains AUTO and we don't know the actual sort
     * type until the values come back.  The fields can only be set once.
     * This method should be synchronized external like all other PQ methods.
     * @param fields
     */
    void setFields (SortField[] fields) throws IOException {
      this.fields = fields;
      this.collators = hasCollators (fields);
      comparators = new FieldComparator[fields.length];
      for(int fieldIDX=0;fieldIDX<fields.length;fieldIDX++) {
        comparators[fieldIDX] = fields[fieldIDX].getComparator(1, fieldIDX);
      }
    }
  
  
    /** Returns the fields being used to sort. */
    SortField[] getFields() {
      return fields;
    }
  
  
    /** Returns an array of collators, possibly <code>null</code>.  The collators
     * correspond to any SortFields which were given a specific locale.
     * @param fields Array of sort fields.
     * @return Array, possibly <code>null</code>.
     */
    private Collator[] hasCollators (final SortField[] fields) {
      if (fields == null) return null;
      Collator[] ret = new Collator[fields.length];
      for (int i=0; i<fields.length; ++i) {
        Locale locale = fields[i].getLocale();
        if (locale != null)
          ret[i] = Collator.getInstance (locale);
      }
      return ret;
    }
  
  
    /**
     * Returns whether <code>a</code> is less relevant than <code>b</code>.
     * @param a ScoreDoc
     * @param b ScoreDoc
     * @return <code>true</code> if document <code>a</code> should be sorted after document <code>b</code>.
     */
    @SuppressWarnings("unchecked") @Override
    protected final boolean lessThan(final FieldDoc docA, final FieldDoc docB) {
      final int n = fields.length;
      int c = 0;
      for (int i=0; i<n && c==0; ++i) {
        final int type = fields[i].getType();
        if (type == SortField.STRING) {
          final String s1 = (String) docA.fields[i];
          final String s2 = (String) docB.fields[i];
          // null values need to be sorted first, because of how FieldCache.getStringIndex()
          // works - in that routine, any documents without a value in the given field are
          // put first.  If both are null, the next SortField is used
          if (s1 == null) {
            c = (s2 == null) ? 0 : -1;
          } else if (s2 == null) {
            c = 1;
          } else if (fields[i].getLocale() == null) {
            c = s1.compareTo(s2);
          } else {
            c = collators[i].compare(s1, s2);
          }
        } else {
          c = comparators[i].compareValues(docA.fields[i], docB.fields[i]);
        }
        // reverse sort
        if (fields[i].getReverse()) {
          c = -c;
        }
      }
  
      // avoid random sort order that could lead to duplicates (bug #31241):
      if (c == 0)
        return docA.doc > docB.doc;
  
      return c > 0;
    }
  }
  