/*
* eXist Open Source Native XML Database
* Copyright (C) 2001-09 Wolfgang M. Meier
* wolfgang@exist-db.org
* http://exist.sourceforge.net
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id$
*/
package org.exist.xquery.functions.text;
import org.exist.dom.Match;
import org.exist.dom.NodeProxy;
import org.exist.dom.QName;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.Dependency;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.Profiler;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.DoubleValue;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.NodeValue;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;
/**
* @author wolf
*/
public class TextRank extends BasicFunction {
public final static FunctionSignature signature = new FunctionSignature(
new QName("text-rank", TextModule.NAMESPACE_URI, TextModule.PREFIX),
"This is just a skeleton for a possible ranking function. Don't use this.",
new SequenceType[]{
new FunctionParameterSequenceType("text", Type.NODE, Cardinality.ZERO_OR_ONE, "The text to rank")},
new FunctionReturnSequenceType(Type.DOUBLE, Cardinality.EXACTLY_ONE, "the ranking of the text"));
public TextRank(XQueryContext context) {
super(context, signature);
}
/* (non-Javadoc)
* @see org.exist.xquery.BasicFunction#eval(org.exist.xquery.value.Sequence[], org.exist.xquery.value.Sequence)
*/
public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
if (context.getProfiler().isEnabled()) {
context.getProfiler().start(this);
context.getProfiler().message(this, Profiler.DEPENDENCIES, "DEPENDENCIES", Dependency.getDependenciesName(this.getDependencies()));
if (contextSequence != null)
{context.getProfiler().message(this, Profiler.START_SEQUENCES, "CONTEXT SEQUENCE", contextSequence);}
}
Sequence result;
// return 0.0 if the argument sequence is empty
//TODO : return empty sequence ?
if(args[0].isEmpty())
{result = DoubleValue.ZERO;}
else {
final NodeValue val = (NodeValue)args[0].itemAt(0);
// Ranking cannot be applied to constructed nodes
if(val.getImplementationType() == NodeValue.IN_MEMORY_NODE)
{throw new XPathException(this, getName() + " cannot be applied to in-memory nodes.");}
final NodeProxy proxy = (NodeProxy)val; // this is a persistent node, so casting is safe
int freq = 0;
Match nextMatch = proxy.getMatches();
// we just count the number of distinct terms matched
while(nextMatch != null) {
freq += nextMatch.getFrequency();
nextMatch = nextMatch.getNextMatch();
}
result = new DoubleValue(freq);
}
if (context.getProfiler().isEnabled())
{context.getProfiler().end(this, "", result);}
return result;
}
}