/**
* Copyright 2014 National University of Ireland, Galway.
*
* This file is part of the SIREn project. Project and contact information:
*
* https://github.com/rdelbru/SIREn
*
* Licensed 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 org.sindice.siren.analysis.filter;
import java.io.IOException;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.sindice.siren.analysis.attributes.NodeAttribute;
import org.sindice.siren.analysis.attributes.PositionAttribute;
/**
* Filter that encode the position relative to the node of each token into
* the {@link PositionAttribute}.
*/
public class PositionAttributeFilter extends TokenFilter {
private final NodeAttribute nodeAtt;
private final PositionAttribute posAtt;
private final PositionIncrementAttribute posIncrAtt;
private long lastNodeHash = Long.MAX_VALUE;
private int lastPosition = 0;
public PositionAttributeFilter(final TokenStream input) {
super(input);
nodeAtt = this.addAttribute(NodeAttribute.class);
posAtt = this.addAttribute(PositionAttribute.class);
posIncrAtt = this.addAttribute(PositionIncrementAttribute.class);
}
@Override
public void reset() throws IOException {
super.reset();
lastPosition = 0;
lastNodeHash = Long.MAX_VALUE;
}
@Override
public final boolean incrementToken() throws IOException {
if (!input.incrementToken()) {
return false;
}
final int nodeHash = nodeAtt.node().hashCode();
if (lastNodeHash != nodeHash) { // new node
lastPosition = 0;
lastNodeHash = nodeHash;
}
lastPosition += posIncrAtt.getPositionIncrement();
if (lastPosition > 0) {
posAtt.setPosition(lastPosition - 1);
}
else {
posAtt.setPosition(lastPosition);
}
return true;
}
}