/*
* This file is part of the DiffX library.
*
* For licensing information please see the file license.txt included in the release.
* A copy of this licence can also be found at
* http://www.opensource.org/licenses/artistic-license-2.0.php
*/
package com.topologi.diffx.load.text;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import com.topologi.diffx.config.TextGranularity;
import com.topologi.diffx.config.WhiteSpaceProcessing;
import com.topologi.diffx.event.TextEvent;
import com.topologi.diffx.event.impl.IgnorableSpaceEvent;
import com.topologi.diffx.event.impl.SpaceEvent;
import com.topologi.diffx.event.impl.WordEvent;
/**
* The tokeniser for characters events.
*
* <p>This class is not synchronized.
*
* @author Christophe Lauret
* @version 11 May 2010
*/
public final class TokenizerByWord implements TextTokenizer {
/**
* Map characters to events in order to recycle events as they are created.
*/
private final Map<String, TextEvent> recycling = new HashMap<String, TextEvent>();
/**
* Define the whitespace processing.
*/
private final WhiteSpaceProcessing whitespace;
/**
* Creates a new tokenizer.
*
* @param whitespace the whitespace processing for this tokenizer.
*
* @throws NullPointerException if the white space processing is not specified.
*/
public TokenizerByWord(WhiteSpaceProcessing whitespace) {
if (whitespace == null) throw new NullPointerException("the white space processing must be specified.");
this.whitespace = whitespace;
}
/**
* {@inheritDoc}
*/
public List<TextEvent> tokenize(CharSequence seq) {
if (seq == null) return null;
if (seq.length() == 0) return Collections.emptyList();
List<TextEvent> events = new ArrayList<TextEvent>(seq.length());
Pattern p = Pattern.compile("\\s+");
Matcher m = p.matcher(seq);
int index = 0;
// Add segments before each match found
while (m.find()) {
if (index != m.start()) {
String word = seq.subSequence(index, m.start()).toString();
events.add(getWordEvent(word));
}
// We don't even need to record a white space if they are ignored!
if (this.whitespace != WhiteSpaceProcessing.IGNORE) {
String space = seq.subSequence(m.start(), m.end()).toString();
events.add(getSpaceEvent(space));
}
index = m.end();
}
// Add remaining word if any
if (index != seq.length()) {
String word = seq.subSequence(index, seq.length()).toString();
events.add(getWordEvent(word));
}
return events;
}
/**
* Always <code>TextGranularity.WORD</code>.
*
* {@inheritDoc}
*/
public TextGranularity granurality() {
return TextGranularity.WORD;
}
// Private helpers ------------------------------------------------------------------------------
/**
* Returns the word event corresponding to the specified characters.
*
* @param word the characters of the word
* @return the corresponding word event
*/
private TextEvent getWordEvent(String word) {
TextEvent e = this.recycling.get(word);
if (e == null) {
e = new WordEvent(word);
this.recycling.put(word, e);
}
return e;
}
/**
* Returns the space event corresponding to the specified characters.
*
* @param space the characters of the space
* @return the corresponding space event
*/
private TextEvent getSpaceEvent(String space) {
// preserve the actual white space used
TextEvent e = this.recycling.get(space);
if (e == null) {
if (this.whitespace == WhiteSpaceProcessing.PRESERVE) {
e = new IgnorableSpaceEvent(space);
} else {
e = SpaceEvent.getInstance(space);
}
this.recycling.put(space, e);
}
return e;
}
}