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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