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>
38     *  How to execute code for node t when a visitor visits node t.  Execute
39     *  pre() before visiting children and execute post() after visiting children.
40     *  </summary>
41     */
42    public interface ITreeVisitorAction
43    {
44        /** <summary>
45         *  Execute an action before visiting children of t.  Return t or
46         *  a rewritten t.  It is up to the visitor to decide what to do
47         *  with the return value.  Children of returned value will be
48         *  visited if using TreeVisitor.visit().
49         *  </summary>
50         */
51        object Pre( object t );
52
53        /** <summary>
54         *  Execute an action after visiting children of t.  Return t or
55         *  a rewritten t.  It is up to the visitor to decide what to do
56         *  with the return value.
57         *  </summary>
58         */
59        object Post( object t );
60    }
61
62    public class TreeVisitorAction
63        : ITreeVisitorAction
64    {
65        private readonly Func<object, object> _preAction;
66        private readonly Func<object, object> _postAction;
67
68        public TreeVisitorAction( Func<object, object> preAction, Func<object, object> postAction )
69        {
70            _preAction = preAction;
71            _postAction = postAction;
72        }
73
74        public object Pre( object t )
75        {
76            if ( _preAction != null )
77                return _preAction( t );
78
79            return t;
80        }
81
82        public object Post( object t )
83        {
84            if ( _postAction != null )
85                return _postAction( t );
86
87            return t;
88        }
89    }
90}
91