/*
 * 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.exoplatform.services.jcr.impl.core.query.lucene;

import org.apache.lucene.search.FieldComparator;

import java.io.IOException;

/**
 * Abstract base class for <code>FieldComparator</code> implementations
 * which are based on values in the form of <code>Comparables</code>.
 */
abstract public class FieldComparatorBase extends FieldComparator<Comparable<?>>
{

   /**
    * The bottom value.
    */
   private Comparable<?> bottom;

   /**
    * Value for a document
    *
    * @param doc  id of the document
    * @return  the value for the given id
    */
   protected abstract Comparable<?> sortValue(int doc);

   /**
    * Retrieves the value of a given slot
    *
    * @param slot  index of the value to retrieve
    * @return  the value in the given slot
    */
   protected abstract Comparable<?> getValue(int slot);

   /**
    * Puts a value into a given slot
    *
    * @param slot  index where to put the value
    * @param value  the value to put into the given slot
    */
   protected abstract void setValue(int slot, Comparable<?> value);

   @Override
   public int compare(int slot1, int slot2)
   {
      return compare(getValue(slot1), getValue(slot2));
   }

   @Override
   public int compareBottom(int doc) throws IOException
   {
      return compare(bottom, sortValue(doc));
   }

   @Override
   public void setBottom(int slot)
   {
      bottom = getValue(slot);
   }

   /**
    * Compare two values
    *
    * @param val1  first value
    * @param val2  second value
    * @return  A negative integer if <code>val1</code> comes before <code>val2</code>,
    *   a positive integer if <code>val1</code> comes after <code>val2</code> and
    *   <code>0</code> if <code>val1</code> and <code>val2</code> are equal.
    */
   protected int compare(Comparable<?> val1, Comparable<?> val2)
   {
      return Util.compare(val1, val2);
   }

   @Override
   public void copy(int slot, int doc) throws IOException
   {
      setValue(slot, sortValue(doc));
   }

   @Override
   public Comparable<?> value(int slot)
   {
      return getValue(slot);
   }
}