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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.scxml.semantics;
18  
19  import java.io.Serializable;
20  import java.util.Comparator;
21  
22  import org.apache.commons.scxml.SCXMLHelper;
23  import org.apache.commons.scxml.model.TransitionTarget;
24  
25  
26  /***
27   * A comparator for TransitionTarget instances.
28   *
29   */
30  final class TransitionTargetComparator implements Comparator, Serializable {
31  
32      /***
33       * Serial version UID.
34       */
35      private static final long serialVersionUID = 1L;
36  
37      /***
38       * Constructor.
39       */
40      TransitionTargetComparator() {
41          super();
42      }
43  
44      /***
45       * Compares two instances of TransitionTarget in terms of the
46       * SCXML tree hierarchy.
47       * <p>Important Remarks:</p> does not fullfill the Comparator contract,
48       * since it returns 0 if o1 == o2 and also if they are not related to each
49       * other and at the same time the chain-to-parent length for o1 is the
50       * same length as for o2 (that is, they are equally deeply nested)
51       *
52       * @param o1 The first TransitionTarget object
53       * @param o2 The second TransitionTarget object
54       * @return int The comparation result
55       * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
56       * @see TransitionTarget
57       */
58      public int compare(final Object o1, final Object o2) {
59          TransitionTarget tt1 = (TransitionTarget) o1;
60          TransitionTarget tt2 = (TransitionTarget) o2;
61          if (tt1 == tt2) {
62              return 0;
63          } else if (SCXMLHelper.isDescendant(tt1, tt2)) {
64              return -1;
65          } else if (SCXMLHelper.isDescendant(tt2, tt1)) {
66              return 1;
67          } else {
68              //the tt1 and tt2 are parallel, now we have to count chain sizes
69              int tc1 = countChainLength(tt1);
70              int tc2 = countChainLength(tt2);
71              //longer the chain, deeper the node is
72              return tc2 - tc1;
73          }
74      }
75  
76      /***
77       * The &quot;depth&quot; at which this TransitionTarget exists in the
78       * SCXML object model.
79       *
80       * @param tt The TransitionTarget
81       * @return int The &quot;depth&quot;
82       */
83      private int countChainLength(final TransitionTarget tt) {
84          int count = 0;
85          TransitionTarget parent = tt.getParent();
86          while (parent != null) {
87              count++;
88              parent = parent.getParent();
89          }
90          return count;
91      }
92  }
93