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 java.io.IOException;
  
  
  /** A Scorer for queries with a required subscorer
   * and an excluding (prohibited) sub DocIdSetIterator.
   * <br>
   * This <code>Scorer</code> implements {@link Scorer#skipTo(int)},
   * and it uses the skipTo() on the given scorers.
   */
  class ReqExclScorer extends Scorer {
    private Scorer reqScorer;
    private DocIdSetIterator exclDisi;
    private int doc = -1;
  
    /** Construct a <code>ReqExclScorer</code>.
     * @param reqScorer The scorer that must match, except where
     * @param exclDisi indicates exclusion.
     */
    public ReqExclScorer(Scorer reqScorer, DocIdSetIterator exclDisi) {
      super(reqScorer.weight);
      this.reqScorer = reqScorer;
      this.exclDisi = exclDisi;
    }
  
    @Override
    public int nextDoc() throws IOException {
      if (reqScorer == null) {
        return doc;
      }
      doc = reqScorer.nextDoc();
      if (doc == NO_MORE_DOCS) {
        reqScorer = null; // exhausted, nothing left
        return doc;
      }
      if (exclDisi == null) {
        return doc;
      }
      return doc = toNonExcluded();
    }
    
    /** Advance to non excluded doc.
     * <br>On entry:
     * <ul>
     * <li>reqScorer != null,
     * <li>exclScorer != null,
     * <li>reqScorer was advanced once via next() or skipTo()
     *      and reqScorer.doc() may still be excluded.
     * </ul>
     * Advances reqScorer a non excluded required doc, if any.
     * @return true iff there is a non excluded required doc.
     */
    private int toNonExcluded() throws IOException {
      int exclDoc = exclDisi.docID();
      int reqDoc = reqScorer.docID(); // may be excluded
      do {  
        if (reqDoc < exclDoc) {
          return reqDoc; // reqScorer advanced to before exclScorer, ie. not excluded
        } else if (reqDoc > exclDoc) {
          exclDoc = exclDisi.advance(reqDoc);
          if (exclDoc == NO_MORE_DOCS) {
            exclDisi = null; // exhausted, no more exclusions
            return reqDoc;
          }
          if (exclDoc > reqDoc) {
            return reqDoc; // not excluded
          }
        }
      } while ((reqDoc = reqScorer.nextDoc()) != NO_MORE_DOCS);
      reqScorer = null; // exhausted, nothing left
      return NO_MORE_DOCS;
    }
  
    @Override
    public int docID() {
      return doc;
    }
  
    /** Returns the score of the current document matching the query.
     * Initially invalid, until {@link #nextDoc()} is called the first time.
     * @return The score of the required scorer.
     */
    @Override
    public float score() throws IOException {
      return reqScorer.score(); // reqScorer may be null when next() or skipTo() already return false
    }
    
    @Override
    public int advance(int target) throws IOException {
      if (reqScorer == null) {
        return doc = NO_MORE_DOCS;
      }
      if (exclDisi == null) {
        return doc = reqScorer.advance(target);
      }
      if (reqScorer.advance(target) == NO_MORE_DOCS) {
        reqScorer = null;
        return doc = NO_MORE_DOCS;
      }
      return doc = toNonExcluded();
    }
  }
  