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    1   /*
    2    *
    3    *   Copyright 2005 The Apache Software Foundation.
    4    *
    5    *  Licensed under the Apache License, Version 2.0 (the "License");
    6    *  you may not use this file except in compliance with the License.
    7    *  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   */
    18  package org.apache.commons.scxml.semantics;
    19
    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 {
    31
    32      /***
    33       * Constructor.
    34       */
    35      TransitionTargetComparator() {
    36          super();
    37      }
    38
    39      /***
    40       * Compares two instances of TransitionTarget in terms of the
    41       * SCXML tree hierarchy.
    42       * <p>Important Remarks:</p> does not fullfill the Comparator contract,
    43       * since it returns 0 if o1 == o2 and also if they are not related to each
    44       * other and at the same time the chain-to-parent length for o1 is the
    45       * same length as for o2 (that is, they are equally deeply nested)
    46       *
    47       * @param o1 The first TransitionTarget object
    48       * @param o2 The second TransitionTarget object
    49       * @return int The comparation result
    50       * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
    51       * @see TransitionTarget
    52       */
    53      public int compare(final Object o1, final Object o2) {
    54          TransitionTarget tt1 = (TransitionTarget) o1;
    55          TransitionTarget tt2 = (TransitionTarget) o2;
    56          if (tt1 == tt2) {
    57              return 0;
    58          } else if (SCXMLHelper.isDescendant(tt1, tt2)) {
    59              return -1;
    60          } else if (SCXMLHelper.isDescendant(tt2, tt1)) {
    61              return 1;
    62          } else {
    63              //the tt1 and tt2 are parallel, now we have to count chain sizes
    64              int tc1 = countChainLength(tt1);
    65              int tc2 = countChainLength(tt2);
    66              //longer the chain, deeper the node is
    67              return tc2 - tc1;
    68          }
    69      }
    70
    71      /***
    72       * The &quot;depth&quot; at which this TransitionTarget exists in the
    73       * SCXML object model.
    74       *
    75       * @param tt The TransitionTarget
    76       * @return int The &quot;depth&quot;
    77       */
    78      private int countChainLength(final TransitionTarget tt) {
    79          int count = 0;
    80          TransitionTarget parent = tt.getParent();
    81          while (parent != null) {
    82              count++;
    83              parent = parent.getParent();
    84          }
    85          return count;
    86      }
    87  }
    88