001/* Copyright (C) 2013 TU Dortmund
002 * This file is part of AutomataLib, http://www.automatalib.net/.
003 * 
004 * AutomataLib is free software; you can redistribute it and/or
005 * modify it under the terms of the GNU Lesser General Public
006 * License version 3.0 as published by the Free Software Foundation.
007 * 
008 * AutomataLib is distributed in the hope that it will be useful,
009 * but WITHOUT ANY WARRANTY; without even the implied warranty of
010 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
011 * Lesser General Public License for more details.
012 * 
013 * You should have received a copy of the GNU Lesser General Public
014 * License along with AutomataLib; if not, see
015 * http://www.gnu.de/documents/lgpl.en.html.
016 */
017package net.automatalib.util.tries;
018
019import java.util.List;
020
021import net.automatalib.words.Word;
022import net.automatalib.words.WordBuilder;
023
024/**
025 * A node in a {@link SuffixTrie}.
026 * 
027 * @author Malte Isberner <malte.isberner@gmail.com>
028 *
029 * @param <I> symbol class.
030 */
031public class SuffixTrieNode<I> extends Word<I> {
032        
033        /**
034         * Optimized iterator for the implicit word representation.
035         * 
036         * @author Malte Isberner <malte.isberner@gmail.com>
037         *
038         * @param <I> symbol class
039         */
040        private static final class Iterator<I> implements java.util.Iterator<I> {
041                
042                private SuffixTrieNode<I> current;
043
044                public Iterator(SuffixTrieNode<I> node) {
045                        this.current = node;
046                }
047                
048                /*
049                 * (non-Javadoc)
050                 * @see java.util.Iterator#hasNext()
051                 */
052                @Override
053                public boolean hasNext() {
054                        return !current.isRoot();
055                }
056
057                /*
058                 * (non-Javadoc)
059                 * @see java.util.Iterator#next()
060                 */
061                @Override
062                public I next() {
063                        I sym = current.symbol;
064                        current = current.parent;
065                        return sym;
066                }
067
068                /*
069                 * (non-Javadoc)
070                 * @see java.util.Iterator#remove()
071                 */
072                @Override
073                public void remove() {
074                        throw new UnsupportedOperationException();
075                }
076        }
077        
078        public static <I> void appendSuffix(SuffixTrieNode<I> node, List<? super I> symList) {
079                while(node.parent != null) {
080                        symList.add(node.symbol);
081                        node = node.parent;
082                }
083        }
084        
085        public static <I> Word<I> toExplicitWord(SuffixTrieNode<I> node) {
086                WordBuilder<I> wb = new WordBuilder<I>(node.depth());
087                appendSuffix(node, wb);
088                return wb.toWord();
089        }
090        
091        public static <I> int depth(SuffixTrieNode<I> node) {
092                int d = 0;
093                while(node.parent != null) {
094                        d++;
095                        node = node.parent;
096                }
097                return d;
098        }
099        
100        public static <I> I getSymbol(SuffixTrieNode<I> node, int index) {
101                while(index-- > 0)
102                        node = node.parent;
103                return node.symbol;
104        }
105        
106        
107        
108        
109        
110        private final I symbol;
111        private final SuffixTrieNode<I> parent;
112        
113
114        /**
115         * Root constructor.
116         */
117        public SuffixTrieNode() {
118                this.symbol = null;
119                this.parent = null;
120        }
121        
122        
123        public SuffixTrieNode(I symbol, SuffixTrieNode<I> parent) {
124                this.symbol = symbol;
125                this.parent = parent;
126        }
127        
128        // TODO: replace by getter/attribute?
129        public int depth() {
130                return depth(this);
131        }
132                
133        public I getSymbol() {
134                return symbol;
135        }
136        
137        public SuffixTrieNode<I> getParent() {
138                return parent;
139        }
140        
141        
142        public boolean isRoot() {
143                return (parent == null);
144        }
145        
146        public void appendSuffix(List<? super I> symList) {
147                appendSuffix(this, symList);
148        }
149        
150        public Word<I> getSuffix() {
151                if(parent == null)
152                        return Word.epsilon();
153                WordBuilder<I> wb = new WordBuilder<>(depth());
154                appendSuffix(wb);
155                return wb.toWord();
156        }
157
158        @Override
159        public I getSymbol(int index) {
160                return getSymbol(this, index);
161        }
162
163        @Override
164        public int length() {
165                return depth();
166        }
167        
168        @Override
169        public Iterator<I> iterator() {
170                return new Iterator<I>(this);
171        }
172}