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1   /***
2    * Redistribution  and use  in source  and binary  forms, with  or without
3    * modification, are permitted provided  that the following conditions are
4    * met :
5    *
6    * . Redistributions  of  source  code  must  retain  the  above copyright
7    *   notice, this list of conditions and the following disclaimer.
8    *
9    * . Redistributions in  binary form  must reproduce  the above  copyright
10   *   notice, this list of conditions  and the following disclaimer in  the
11   *   documentation and/or other materials provided with the distribution.
12   *
13   * . The name of the author may not be used to endorse or promote products
14   *   derived from this software without specific prior written permission.
15   *
16   * THIS SOFTWARE IS  PROVIDED BY THE  AUTHOR ``AS IS''  AND ANY EXPRESS  OR
17   * IMPLIED  WARRANTIES,  INCLUDING,  BUT   NOT  LIMITED  TO,  THE   IMPLIED
18   * WARRANTIES OF MERCHANTABILITY AND  FITNESS FOR A PARTICULAR  PURPOSE ARE
19   * DISCLAIMED.  IN NO  EVENT SHALL  THE AUTHOR  BE LIABLE  FOR ANY  DIRECT,
20   * INDIRECT,  INCIDENTAL,  SPECIAL,  EXEMPLARY,  OR  CONSEQUENTIAL  DAMAGES
21   * (INCLUDING,  BUT  NOT LIMITED  TO,  PROCUREMENT OF  SUBSTITUTE  GOODS OR
22   * SERVICES;  LOSS  OF USE,  DATA,  OR PROFITS;  OR  BUSINESS INTERRUPTION)
23   * HOWEVER CAUSED  AND ON  ANY THEORY  OF LIABILITY,  WHETHER IN  CONTRACT,
24   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
25   * ANY  WAY  OUT OF  THE  USE OF  THIS  SOFTWARE, EVEN  IF  ADVISED OF  THE
26   * POSSIBILITY OF SUCH DAMAGE.
27   *
28   * $Id$
29   */
30  
31  package palmed.edit.selection;
32  
33  import java.io.InputStream;
34  import java.io.OutputStream;
35  import java.util.Stack;
36  import palmed.io.ISerializable;
37  
38  /***
39   * This class implements an undo manager.
40   *
41   * @author Mathieu Champlon
42   * @version $Revision$ $Date$
43   */
44  public final class UndoManager implements ISerializable
45  {
46      /***
47       * The undo actions.
48       */
49      private final Stack undo_;
50      /***
51       * The redo actions.
52       */
53      private final Stack redo_;
54      /***
55       * The size of the undo stack.
56       */
57      private final int size_;
58      /***
59       * Whether the next merge should be skipped or not.
60       */
61      private boolean skipNext_;
62  
63      /***
64       * Create an undo/redo manager.
65       *
66       * @param size the size of the undo stack.
67       */
68      public UndoManager( final int size )
69      {
70          undo_ = new Stack();
71          redo_ = new Stack();
72          size_ = size;
73      }
74  
75      /***
76       * Undo the last action.
77       */
78      public void undo()
79      {
80          if( !undo_.isEmpty() )
81          {
82              final IAction action = (IAction)undo_.pop();
83              action.undo();
84              redo_.push( action );
85          }
86      }
87  
88      /***
89       * Redo the last undone action.
90       */
91      public void redo()
92      {
93          if( !redo_.isEmpty() )
94          {
95              final IAction action = (IAction)redo_.pop();
96              action.redo();
97              undo_.push( action );
98          }
99      }
100 
101     /***
102      * Add an action to the undo list.
103      *
104      * @param action the action
105      */
106     public void add( final IAction action )
107     {
108         if( action != null )
109         {
110             if( !merge( action ) )
111                 undo_.addElement( action );
112             redo_.removeAllElements();
113             if( undo_.size() > size_ )
114                 undo_.removeElementAt( 0 );
115         }
116     }
117 
118     private boolean merge( final IAction action )
119     {
120         if( undo_.isEmpty() )
121             return false;
122         if( skipNext_ )
123         {
124             skipNext_ = false;
125             return false;
126         }
127         return ((IAction)undo_.peek()).merge( action );
128     }
129 
130     /***
131      * Clear the undo and redo lists.
132      */
133     public void clear()
134     {
135         undo_.removeAllElements();
136         redo_.removeAllElements();
137     }
138 
139     /***
140      * {@inheritDoc}
141      */
142     public void marshall( final OutputStream stream )
143     {
144         clear(); // TODO TMP ?
145     }
146 
147     /***
148      * {@inheritDoc}
149      */
150     public void unmarshall( final InputStream stream )
151     {
152         clear(); // TODO TMP ?
153     }
154 
155     /***
156      * Skip the next merge.
157      */
158     public void skip()
159     {
160         skipNext_ = true;
161     }
162 }