package org.madore.damlengine;

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

public class LangHelper {

    public static final String LANG = "lang";

    public static String getLangNorec(Node node) {
	// Returns null when no xml:lang attribute is found,
	// otherwise, returns its value.
	if ( node instanceof Element ) {
	    Attr lang = ((Element)node).
		getAttributeNodeNS(DamlEngine.XML_NS, LANG);
	    if ( lang == null )
		return null;
	    else
		return lang.getValue();
	} else
	    return null;
    }

    public static void setLangNorec(Element node, String lang) {
	if ( lang == null )
	    throw new NullPointerException("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 void setWeakLangNorec(Element node, String lang) {
	if ( lang == null )
	    throw new NullPointerException("lang is null in setWeakLangNorec");
	String currentLang = getLangNorec(node);
	if ( currentLang == null )
	    setLangNorec(node,lang);
    }

    public static String getLangRec(Node node) {
	// Never returns null (returns the empty string for no language).
	// node may be null (in which case, return "").
	while ( node != null ) {
	    String lang = getLangNorec(node);
	    if ( lang != null )
		return lang;
	    node = node.getParentNode();
	}
	return "";
    }

    public static void setLangRec(Element node, String lang) {
	if ( lang == null )
	    throw new NullPointerException("lang is null in setLangRec");
	String parentLang = getLangRec(node.getParentNode());
	if ( lang.equals(parentLang) )
	    unsetLangNorec(node);
	else
	    setLangNorec(node,lang);
    }

}