content: package org.apache.lucene.search.spans;
  
  /**
   * 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 java.util.Set;
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.search.Query;
  import org.apache.lucene.search.Weight;
  import org.apache.lucene.search.Searcher;
  import org.apache.lucene.search.Similarity;
  import org.apache.lucene.util.ToStringUtils;
  
  /**
   * <p>Wrapper to allow {@link SpanQuery} objects participate in composite 
   * single-field SpanQueries by 'lying' about their search field. That is, 
   * the masked SpanQuery will function as normal, 
   * but {@link SpanQuery#getField()} simply hands back the value supplied 
   * in this class's constructor.</p>
   * 
   * <p>This can be used to support Queries like {@link SpanNearQuery} or 
   * {@link SpanOrQuery} across different fields, which is not ordinarily 
   * permitted.</p>
   * 
   * <p>This can be useful for denormalized relational data: for example, when 
   * indexing a document with conceptually many 'children': </p>
   * 
   * <pre>
   *  teacherid: 1
   *  studentfirstname: james
   *  studentsurname: jones
   *  
   *  teacherid: 2
   *  studenfirstname: james
   *  studentsurname: smith
   *  studentfirstname: sally
   *  studentsurname: jones
   * </pre>
   * 
   * <p>a SpanNearQuery with a slop of 0 can be applied across two 
   * {@link SpanTermQuery} objects as follows:
   * <pre>
   *    SpanQuery q1  = new SpanTermQuery(new Term("studentfirstname", "james"));
   *    SpanQuery q2  = new SpanTermQuery(new Term("studentsurname", "jones"));
   *    SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
   *    Query q = new SpanNearQuery(new SpanQuery[]{q1, q2m}, -1, false);
   * </pre>
   * to search for 'studentfirstname:james studentsurname:jones' and find 
   * teacherid 1 without matching teacherid 2 (which has a 'james' in position 0 
   * and 'jones' in position 1). </p>
   * 
   * <p>Note: as {@link #getField()} returns the masked field, scoring will be 
   * done using the norms of the field name supplied. This may lead to unexpected
   * scoring behaviour.</p>
   */
  public class FieldMaskingSpanQuery extends SpanQuery {
    private SpanQuery maskedQuery;
    private String field;
      
    public FieldMaskingSpanQuery(SpanQuery maskedQuery, String maskedField) {
      this.maskedQuery = maskedQuery;
      this.field = maskedField;
    }
  
    @Override
    public String getField() {
      return field;
    }
  
    public SpanQuery getMaskedQuery() {
      return maskedQuery;
    }
  
    // :NOTE: getBoost and setBoost are not proxied to the maskedQuery
    // ...this is done to be more consistent with things like SpanFirstQuery
    
    @Override
    public Spans getSpans(IndexReader reader) throws IOException {
      return maskedQuery.getSpans(reader);
    }
  
    @Override
    public void extractTerms(Set<Term> terms) {
      maskedQuery.extractTerms(terms);
    }  
  
    @Override
    public Weight createWeight(Searcher searcher) throws IOException {
      return maskedQuery.createWeight(searcher);
    }
  
    @Override
    public Query rewrite(IndexReader reader) throws IOException {
      FieldMaskingSpanQuery clone = null;
  
      SpanQuery rewritten = (SpanQuery) maskedQuery.rewrite(reader);
      if (rewritten != maskedQuery) {
        clone = (FieldMaskingSpanQuery) this.clone();
        clone.maskedQuery = rewritten;
      }
  
      if (clone != null) {
        return clone;
      } else {
        return this;
      }
    }
  
    @Override
    public String toString(String field) {
      StringBuilder buffer = new StringBuilder();
      buffer.append("mask(");
      buffer.append(maskedQuery.toString(field));
      buffer.append(")");
      buffer.append(ToStringUtils.boost(getBoost()));
      buffer.append(" as ");
      buffer.append(this.field);
      return buffer.toString();
    }
    
    @Override
    public boolean equals(Object o) {
      if (!(o instanceof FieldMaskingSpanQuery))
        return false;
      FieldMaskingSpanQuery other = (FieldMaskingSpanQuery) o;
      return (this.getField().equals(other.getField())
              && (this.getBoost() == other.getBoost())
              && this.getMaskedQuery().equals(other.getMaskedQuery()));
  
    }
    
    @Override
    public int hashCode() {
      return getMaskedQuery().hashCode()
        ^ getField().hashCode()
        ^ Float.floatToRawIntBits(getBoost());
    }
  }
  