/*
 *  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.util;

import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;

import org.apache.log4j.Logger;
import org.exist.dom.QName;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.Module;
import org.exist.xquery.UserDefinedFunction;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.QNameValue;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;

/**
 * Returns a sequence containing the QNames of all built-in functions
 * currently registered in the query engine.
 * 
 * @author wolf
 */
public class BuiltinFunctions extends BasicFunction {
	
	protected static final Logger logger = Logger.getLogger(BuiltinFunctions.class);

	public final static FunctionSignature signatures[] = {
		new FunctionSignature(
				new QName("registered-functions", UtilModule.NAMESPACE_URI, UtilModule.PREFIX),
				"Returns a sequence containing the QNames of all functions " +
				"declared in the module identified by the specified namespace URI. " +
				"An error is raised if no module is found for the specified URI.",
				new SequenceType[] { new FunctionParameterSequenceType("namespace-uri", Type.STRING, Cardinality.EXACTLY_ONE, "The namespace URI of the function module") },
				new FunctionReturnSequenceType(Type.STRING, Cardinality.ONE_OR_MORE, "the sequence of function names")),
		new FunctionSignature(
			new QName("registered-functions", UtilModule.NAMESPACE_URI, UtilModule.PREFIX),
			"Returns a sequence containing the QNames of all functions " +
			"currently known to the system, including functions in imported and built-in modules.",
			null,
			new FunctionReturnSequenceType(Type.STRING, Cardinality.ONE_OR_MORE, "the sequence of function names")),
	};

	public BuiltinFunctions(XQueryContext context, FunctionSignature signature) {
		super(context, signature);
	}

	/* (non-Javadoc)
	 * @see org.exist.xquery.Expression#eval(org.exist.dom.DocumentSet, org.exist.xquery.value.Sequence, org.exist.xquery.value.Item)
	 */
	public Sequence eval(Sequence[] args,	Sequence contextSequence)
		throws XPathException {
		
		ValueSequence resultSeq = new ValueSequence();
		if(getSignature().getArgumentCount() == 1) {
			String uri = args[0].getStringValue();
			Module module = context.getModule(uri);
			if(module == null)
				throw new XPathException(this, "No module found matching namespace URI: " + uri);
			addFunctionsFromModule(resultSeq, module);
		} else {
			for(Iterator i = context.getModules(); i.hasNext(); ) {
				Module module = (Module)i.next();
				addFunctionsFromModule(resultSeq, module);
			}
			// Add all functions declared in the local module
			for(Iterator i = context.localFunctions(); i.hasNext(); ) {
				UserDefinedFunction func = (UserDefinedFunction)i.next();
				FunctionSignature sig = func.getSignature();
				resultSeq.add(new QNameValue(context, sig.getName()));
			}
		}
		return resultSeq;
	}

	private void addFunctionsFromModule(ValueSequence resultSeq, Module module) {
		Set set = new TreeSet();
		FunctionSignature signatures[] = module.listFunctions();
		// add to set to remove duplicate QName's
		for(int j = 0; j < signatures.length; j++) {
			QName qname = signatures[j].getName();
			set.add(qname);
		}
		for(Iterator it = set.iterator(); it.hasNext(); ) {
			QName qname = (QName)it.next();
			resultSeq.add(new QNameValue(context, qname));
		}
	}

}