/*
 * 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.hadoop.hbase.codec.prefixtree.encode.tokenize;

import java.util.Comparator;

import org.apache.hadoop.classification.InterfaceAudience;

/**
 * Determines order of nodes in the output array.  Maybe possible to optimize further.
 */
@InterfaceAudience.Private
public class TokenDepthComparator implements Comparator<TokenizerNode> {

  @Override
  public int compare(TokenizerNode a, TokenizerNode b) {
    if(a==null){
      throw new IllegalArgumentException("a cannot be null");
    }
    if(b==null){
      throw new IllegalArgumentException("b cannot be null");
    }

    // put leaves at the end
    if (!a.isLeaf() && b.isLeaf()) {
      return -1;
    }
    if (a.isLeaf() && !b.isLeaf()) {
      return 1;
    }

    if (a.isLeaf() && b.isLeaf()) {// keep leaves in sorted order (for debugability)
      return a.getId() < b.getId() ? -1 : 1;
    }

    // compare depth
    if (a.getTokenOffset() < b.getTokenOffset()) {
      return -1;
    }
    if (a.getTokenOffset() > b.getTokenOffset()) {
      return 1;
    }

    // if same depth, return lower id first. ids are unique
    return a.getId() < b.getId() ? -1 : 1;
  }

}
