1/*
2 * [The "BSD licence"]
3 * Copyright (c) 2005-2008 Terence Parr
4 * All rights reserved.
5 *
6 * Conversion to C#:
7 * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
8 * All rights reserved.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote products
19 *    derived from this software without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33namespace Antlr.Runtime.Tree
34{
35    using Antlr.Runtime.Misc;
36
37    /** <summary>Do a depth first walk of a tree, applying pre() and post() actions as we go.</summary> */
38    public class TreeVisitor
39    {
40        protected ITreeAdaptor adaptor;
41
42        public TreeVisitor( ITreeAdaptor adaptor )
43        {
44            this.adaptor = adaptor;
45        }
46        public TreeVisitor()
47            : this( new CommonTreeAdaptor() )
48        {
49        }
50
51        /** <summary>
52         *  Visit every node in tree t and trigger an action for each node
53         *  before/after having visited all of its children.  Bottom up walk.
54         *  Execute both actions even if t has no children.  Ignore return
55         *  results from transforming children since they will have altered
56         *  the child list of this node (their parent).  Return result of
57         *  applying post action to this node.
58         *  </summary>
59         */
60        public object Visit( object t, ITreeVisitorAction action )
61        {
62            // System.out.println("visit "+((Tree)t).toStringTree());
63            bool isNil = adaptor.IsNil( t );
64            if ( action != null && !isNil )
65            {
66                t = action.Pre( t ); // if rewritten, walk children of new t
67            }
68            for ( int i = 0; i < adaptor.GetChildCount(t); i++ )
69            {
70                object child = adaptor.GetChild( t, i );
71                Visit( child, action );
72            }
73            if ( action != null && !isNil )
74                t = action.Post( t );
75            return t;
76        }
77
78        public object Visit( object t, Func<object, object> preAction, Func<object, object> postAction )
79        {
80            return Visit( t, new TreeVisitorAction( preAction, postAction ) );
81        }
82    }
83}
84