/*
 * 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;

import java.io.IOException;
import java.util.List;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.ReaderUtil;
import org.apache.lucene.search.LongValues;
import org.apache.lucene.search.LongValuesSource;


 Dictionary with terms and optionally payload and optionally contexts information taken from stored fields in a Lucene index. Similar to DocumentDictionary, except it obtains the weight of the terms in a document based on a LongValuesSource. 
NOTE: 
 

   

     The term field has to be stored; if it is missing, the document is skipped.
   
   

     The payload and contexts field are optional and are not required to be stored.
   
 
 
 In practice the LongValuesSource will likely be obtained using the lucene expression module. The following example shows how to create a LongValuesSource from a simple addition of two fields: 
   Expression expression = JavascriptCompiler.compile("f1 + f2");
   SimpleBindings bindings = new SimpleBindings();
   bindings.add(new SortField("f1", SortField.Type.LONG));
   bindings.add(new SortField("f2", SortField.Type.LONG));
   LongValuesSource valueSource = expression.getDoubleValuesSource(bindings).toLongValuesSource();
 
 
/**
 * <p>
 * Dictionary with terms and optionally payload and
 * optionally contexts information
 * taken from stored fields in a Lucene index. Similar to 
 * {@link DocumentDictionary}, except it obtains the weight
 * of the terms in a document based on a {@link LongValuesSource}.
 * </p>
 * <b>NOTE:</b> 
 *  <ul>
 *    <li>
 *      The term field has to be stored; if it is missing, the document is skipped.
 *    </li>
 *    <li>
 *      The payload and contexts field are optional and are not required to be stored.
 *    </li>
 *  </ul>
 *  <p>
 *  In practice the {@link LongValuesSource} will likely be obtained
 *  using the lucene expression module. The following example shows
 *  how to create a {@link LongValuesSource} from a simple addition of two
 *  fields:
 *  <code>
 *    Expression expression = JavascriptCompiler.compile("f1 + f2");
 *    SimpleBindings bindings = new SimpleBindings();
 *    bindings.add(new SortField("f1", SortField.Type.LONG));
 *    bindings.add(new SortField("f2", SortField.Type.LONG));
 *    LongValuesSource valueSource = expression.getDoubleValuesSource(bindings).toLongValuesSource();
 *  </code>
 *  </p>
 *
 */
public class DocumentValueSourceDictionary extends DocumentDictionary {
  
  private final LongValuesSource weightsValueSource;

  
Creates a new dictionary with the contents of the fields named field
for the terms, payload for the corresponding payloads, contexts
for the associated contexts and uses the weightsValueSource supplied
to determine the score.
/**
   * Creates a new dictionary with the contents of the fields named <code>field</code>
   * for the terms, <code>payload</code> for the corresponding payloads, <code>contexts</code>
   * for the associated contexts and uses the <code>weightsValueSource</code> supplied
   * to determine the score.
   */
  public DocumentValueSourceDictionary(IndexReader reader, String field,
                                       LongValuesSource weightsValueSource, String payload, String contexts) {
    super(reader, field, null, payload, contexts);
    this.weightsValueSource = weightsValueSource;
  }

  
Creates a new dictionary with the contents of the fields named field
for the terms, payloadField for the corresponding payloads
and uses the weightsValueSource supplied to determine the
score.
/**
   * Creates a new dictionary with the contents of the fields named <code>field</code>
   * for the terms, <code>payloadField</code> for the corresponding payloads
   * and uses the <code>weightsValueSource</code> supplied to determine the
   * score.
   */
  public DocumentValueSourceDictionary(IndexReader reader, String field,
                                       LongValuesSource weightsValueSource, String payload) {
    super(reader, field, null, payload);
    this.weightsValueSource = weightsValueSource;
  }

  
Creates a new dictionary with the contents of the fields named field
for the terms and uses the weightsValueSource supplied to determine the
score.
/**
   * Creates a new dictionary with the contents of the fields named <code>field</code>
   * for the terms and uses the <code>weightsValueSource</code> supplied to determine the
   * score.
   */
  public DocumentValueSourceDictionary(IndexReader reader, String field,
                                       LongValuesSource weightsValueSource) {
    super(reader, field, null, null);
    this.weightsValueSource = weightsValueSource;
  }
  
  @Override
  public InputIterator getEntryIterator() throws IOException {
    return new DocumentValueSourceInputIterator(payloadField!=null, contextsField!=null);
  }
  
  final class DocumentValueSourceInputIterator extends DocumentDictionary.DocumentInputIterator {
    
    private LongValues currentWeightValues;
    
leaves of the reader /** leaves of the reader */
    private final List<LeafReaderContext> leaves;
    
starting docIds of all the leaves /** starting docIds of all the leaves */
    private final int[] starts;
    
current leave index /** current leave index */
    private int currentLeafIndex = 0;

    public DocumentValueSourceInputIterator(boolean hasPayloads, boolean hasContexts)
        throws IOException {
      super(hasPayloads, hasContexts);
      leaves = reader.leaves();
      starts = new int[leaves.size() + 1];
      for (int i = 0; i < leaves.size(); i++) {
        starts[i] = leaves.get(i).docBase;
      }
      starts[leaves.size()] = reader.maxDoc();
      currentWeightValues = (leaves.size() > 0) 
          ? weightsValueSource.getValues(leaves.get(currentLeafIndex), null)
          : null;
    }
    
    
Returns the weight for the current docId as computed 
by the weightsValueSource
/** 
     * Returns the weight for the current <code>docId</code> as computed 
     * by the <code>weightsValueSource</code>
     * */
    @Override
    protected long getWeight(Document doc, int docId) throws IOException {
      if (currentWeightValues == null) {
        return 0;
      }
      int subIndex = ReaderUtil.subIndex(docId, starts);
      if (subIndex != currentLeafIndex) {
        currentLeafIndex = subIndex;
        currentWeightValues = weightsValueSource.getValues(leaves.get(currentLeafIndex), null);
      }
      if (currentWeightValues.advanceExact(docId - starts[subIndex]))
        return currentWeightValues.longValue();
      else
        return 0;

    }

  }
}