package org.madore.damlengine;

import org.w3c.dom.Node;
import org.w3c.dom.Element;

public class LangHelper {

    public static final String LANG = "lang";

    public static String getLangNorec(Node node) {
	if ( node instanceof Element )
	    return ((Element)node).getAttributeNS(DamlEngine.XML_NS, LANG);
	else
	    return null;
    }

    public static void setLangNorec(Element node, String lang) {
	if ( lang == null )
	    throw new Error("lang is null in setLangNorec");
	node.setAttributeNS(DamlEngine.XML_NS, LANG, lang);
    }

    public static void unsetLangNorec(Element node) {
	node.removeAttributeNS(DamlEngine.XML_NS, LANG);
    }

    public static String getLangRec(Node node) {
	// node may be null (in which case, return null)
	while ( node != null ) {
	    String lang = getLangNorec(node);
	    if ( lang != null )
		return lang;
	    node = node.getParentNode();
	}
	return null;
    }

    public static void setLangRec(Element node, String lang) {
	if ( lang == null )
	    throw new Error("lang is null in setLangRec");
	Node parentNode = node.getParentNode();
	String parentLang = (parentNode!=null)?getLangNorec(parentNode):null;
	if ( parentLang != null && lang.equals(parentLang) )
	    unsetLangNorec(node);
	else
	    setLangNorec(node,lang);
    }

}