/*******************************************************************************
 * Copyright (c) 2005, 2010 Andrea Bittau, University College London, and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Andrea Bittau - initial API and implementation from the PsychoPath XPath 2.0 
 *     David Carver (STAR) - bug 288886 - add unit tests and fix fn:resolve-qname function
 *     Mukul Gandhi - bug 280798 - PsychoPath support for JDK 1.4
 *******************************************************************************/

package org.eclipse.wst.xml.xpath2.processor.internal.function;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

import org.eclipse.wst.xml.xpath2.api.EvaluationContext;
import org.eclipse.wst.xml.xpath2.api.ResultBuffer;
import org.eclipse.wst.xml.xpath2.api.ResultSequence;
import org.eclipse.wst.xml.xpath2.api.StaticContext;
import org.eclipse.wst.xml.xpath2.processor.DynamicError;
import org.eclipse.wst.xml.xpath2.processor.internal.SeqType;
import org.eclipse.wst.xml.xpath2.processor.internal.types.ElementType;
import org.eclipse.wst.xml.xpath2.processor.internal.types.QName;
import org.eclipse.wst.xml.xpath2.processor.internal.types.XSString;
import org.w3c.dom.Element;

/**
 * Returns an xs:QName value (that is, an expanded-QName) by taking an xs:string
 * that has the lexical form of an xs:QName (a string in the form
 * "prefix:local-name" or "local-name") and resolving it using the in-scope
 * namespaces for a given element.
 */
public class FnResolveQName extends Function {
	private static Collection _expected_args = null;

	/**
	 * Constructor for FnResolveQName.
	 */
	public FnResolveQName() {
		super(new QName("resolve-QName"), 2);
	}

	/**
	 * Evaluate arguments.
	 * 
	 * @param args
	 *            argument expressions.
	 * @throws DynamicError
	 *             Dynamic error.
	 * @return Result of evaluation.
	 */
	public ResultSequence evaluate(Collection args, EvaluationContext ec) throws DynamicError {
		return resolve_QName(args, ec.getStaticContext());
	}

	/**
	 * Resolve-QName operation.
	 * 
	 * @param args
	 *            Result from the expressions evaluation.
	 * @param sc
	 *            Result of static context operation.
	 * @throws DynamicError
	 *             Dynamic error.
	 * @return Result of fn:resolve-QName operation.
	 */
	public static ResultSequence resolve_QName(Collection args, StaticContext sc)
			throws DynamicError {

		//Collection cargs = Function.convert_arguments(args, expected_args());
		Collection cargs = args;

		// get args
		Iterator argiter = cargs.iterator();
		ResultSequence arg1 = (ResultSequence) argiter.next();

		if (arg1.empty())
			return ResultBuffer.EMPTY;
		
		ResultSequence arg2 = (ResultSequence) argiter.next();

		String name = ((XSString) arg1.first()).value();

		QName qn = QName.parse_QName(name);

		if (qn == null)
			throw DynamicError.lexical_error(null);

		ElementType xselement = (ElementType) arg2.first();
		Element element = (Element) xselement.node_value();

		if (qn.prefix() != null) {
			String namespaceURI = element.lookupNamespaceURI(qn.prefix());
			
			if (namespaceURI == null) {
				throw DynamicError.invalidPrefix();
			}
			qn.set_namespace(namespaceURI);
		} else {
			if (qn.local().equals(element.getLocalName()) && element.isDefaultNamespace(element.getNamespaceURI())) {
				qn.set_namespace(element.getNamespaceURI());
			}
		}
		

		return qn;
	}

	/**
	 * Obtain a list of expected arguments.
	 * 
	 * @return Result of operation.
	 */
	public synchronized static Collection expected_args() {
		if (_expected_args == null) {
			_expected_args = new ArrayList();
			SeqType arg = new SeqType(new XSString(), SeqType.OCC_QMARK);
			_expected_args.add(arg);
			_expected_args
					.add(new SeqType(new ElementType(), SeqType.OCC_NONE));
		}

		return _expected_args;
	}
}