eu.project.ttc.resources.PrefixTree.java Source code

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Here is the source code for eu.project.ttc.resources.PrefixTree.java

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/*******************************************************************************
 * Copyright 2015-2016 - CNRS (Centre National de Recherche Scientifique)
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 *
 *******************************************************************************/

package eu.project.ttc.resources;

import java.io.IOException;
import java.io.InputStream;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;
import java.util.Scanner;

import org.apache.commons.io.IOUtils;
import org.apache.uima.resource.DataResource;
import org.apache.uima.resource.ResourceInitializationException;
import org.apache.uima.resource.SharedResourceObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

import eu.project.ttc.utils.TermSuiteConstants;

public class PrefixTree implements SharedResourceObject {
    private static final Logger LOGGER = LoggerFactory.getLogger(PrefixTree.class);

    public static final String PREFIX_TREE = "PrefixTree";

    private Node rootNode = new Node(Node.ROOT_CHAR);

    private static class Node {
        public static final char ROOT_CHAR = '^';
        private boolean validPrefix;
        private char character;
        private Node parent;
        private Map<Character, Node> children = Maps.newHashMap();

        public Node(char character) {
            super();
            this.character = character;
        }

        public void indexString(Queue<Character> charSequence) {
            indexString(charSequence, 0);
        }

        private void indexString(Queue<Character> charSequence, int depth) {
            if (charSequence.isEmpty()) {
                Preconditions.checkArgument(!(isRoot() && depth == 0), "Empty string is not a valid prefix");
                this.validPrefix = true;
            } else {
                Character c = charSequence.poll();
                Node childNode;
                if (children.containsKey(c))
                    childNode = children.get(c);
                else {
                    childNode = new Node(c);
                    childNode.parent = this;
                    children.put(c, childNode);
                }

                childNode.indexString(charSequence, depth + 1);
            }
        }

        public String getPrefix(Queue<Character> charSequence) {
            return getPrefix(charSequence, null, 0);
        }

        public String getPrefix(Queue<Character> charSequence, String lastPrefixFound, int depth) {
            if (validPrefix)
                lastPrefixFound = toPrefixString();
            if (charSequence.isEmpty())
                return lastPrefixFound;
            else {
                Character c = charSequence.poll();
                if (children.containsKey(c)) {
                    Node child = children.get(c);
                    return child.getPrefix(charSequence, lastPrefixFound, depth + 1);
                } else
                    return lastPrefixFound;
            }

        }

        private String toPrefixString() {
            return toPrefixString(new StringBuffer());
        }

        private String toPrefixString(StringBuffer buffer) {
            if (isRoot()) {
                return buffer.reverse().toString();
            } else {
                buffer.append(this.character);
                return parent.toPrefixString(buffer);
            }
        }

        private boolean isRoot() {
            return this.character == ROOT_CHAR;
        }
    }

    @Override
    public void load(DataResource data) throws ResourceInitializationException {
        InputStream inputStream = null;
        try {
            inputStream = data.getInputStream();
            Scanner scanner = null;
            try {
                String line;
                scanner = new Scanner(inputStream, "UTF-8");
                scanner.useDelimiter(TermSuiteConstants.LINE_BREAK);
                while (scanner.hasNext()) {
                    line = scanner.next().split(TermSuiteConstants.DIESE)[0].trim();
                    if (line.startsWith("#"))
                        continue;
                    else if (line.isEmpty())
                        continue;
                    else if (line.endsWith("-")) {
                        if (line.length() == 1)
                            continue;
                        else
                            line = line.substring(0, line.length() - 1);
                    }

                    rootNode.indexString(toCharQueue(line));
                }
            } catch (Exception e) {
                e.printStackTrace();
                throw new ResourceInitializationException(e);
            } finally {
                IOUtils.closeQuietly(scanner);
            }
        } catch (IOException e) {
            LOGGER.error("Could not load file {}", data.getUrl());
            throw new ResourceInitializationException(e);
        } finally {
            IOUtils.closeQuietly(inputStream);
        }

    }

    public String getPrefix(String word) {
        return rootNode.getPrefix(toCharQueue(word));
    }

    private Queue<Character> toCharQueue(String line) {
        LinkedList<Character> characters = Lists.newLinkedList();
        for (int i = 0; i < line.length(); i++)
            characters.add(line.charAt(i));
        return characters;
    }

}