/*
 *  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.session;

import org.apache.log4j.Logger;
import org.exist.dom.QName;
import org.exist.http.servlets.SessionWrapper;
import org.exist.xquery.Cardinality;
import org.exist.xquery.Dependency;
import org.exist.xquery.Function;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.Profiler;
import org.exist.xquery.Variable;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.Item;
import org.exist.xquery.value.JavaObjectValue;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;

/**
 * @author Wolfgang Meier
 * @author Loren Cahlander
 */
public class SetAttribute extends Function 
{
	private static final Logger logger = Logger.getLogger(SetAttribute.class);
	
	public final static FunctionSignature signature =
		new FunctionSignature(
			new QName( "set-attribute", SessionModule.NAMESPACE_URI, SessionModule.PREFIX ),
			"Stores a value in the current session using the supplied attribute name. If no session exists, then one will be created.",
			new SequenceType[] {
				new FunctionParameterSequenceType( "name", Type.STRING, Cardinality.EXACTLY_ONE, "The attribute name" ),
				new FunctionParameterSequenceType( "value", Type.ITEM, Cardinality.ZERO_OR_MORE, "The value to be stored in the session by the attribute name" )
			},
			new SequenceType( Type.ITEM, Cardinality.EMPTY ) );
	
	
	public SetAttribute( XQueryContext context ) 
	{
		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 contextSequence, Item contextItem ) throws XPathException 
	{

		JavaObjectValue session;
		
        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 );
			}

            if( contextItem != null ) {
                context.getProfiler().message( this, Profiler.START_SEQUENCES, "CONTEXT ITEM", contextItem.toSequence() );
			}
        }
        
		SessionModule myModule = (SessionModule)context.getModule( SessionModule.NAMESPACE_URI );

		// session object is read from global variable $session
		Variable var = myModule.resolveVariable( SessionModule.SESSION_VAR );
		
		if( var == null || var.getValue() == null ) {
			// No saved session, so create one
			session = SessionModule.createSession( context, this );
		} else if( var.getValue().getItemType() != Type.JAVA_OBJECT ) {
			throw( new XPathException( this, "Variable $session is not bound to a Java object." ) );
		} else {
			session = (JavaObjectValue)var.getValue().itemAt( 0 );
		}
		
		// get attribute name parameter
		String attribName = getArgument(0).eval( contextSequence, contextItem ).getStringValue();
		Sequence attribValue = getArgument(1).eval( contextSequence, contextItem) ;
		
		if( session.getObject() instanceof SessionWrapper ) {
			((SessionWrapper)session.getObject()).setAttribute (attribName, attribValue );
		} else {
			throw( new XPathException( this, "Type error: variable $session is not bound to a session object" ) );
		}

		return( Sequence.EMPTY_SEQUENCE );
	}
}