import java.util.Enumeration;
import org.xml.sax.*;
import org.xml.sax.ext.LexicalHandler;
import org.xml.sax.helpers.AttributesImpl;
import RssChannel.RssItem;


interface RssHandler {
    void channelUpdate (RssChannel c) throws SAXException;
}

/**
 * Marshaling RSS Data to SAX Events
 */
public class RssProducer implements RssHandler
{
    private static char		lineEnd [] = { '\n', '\t', '\t', '\t' };
    private ContentHandler	content;
    private LexicalHandler	lexical;

    public RssProducer (ContentHandler n)
	{ content = n; }
    
    public void setLexicalHandler (LexicalHandler l)
	{ lexical = l; }

    private void doIndent (int n)
    throws SAXException
    {
	n++;	// NL
	if (n > lineEnd.length)
	    n = lineEnd.length;
	content.ignorableWhitespace (lineEnd, 0, n);
    }

    private void element (int indent, String name, String val, Attributes atts)
    throws SAXException
    {
	char	contents [] = val.toCharArray ();

	doIndent (indent);
	content.startElement ("", "", name, atts);
	content.characters (contents, 0, contents.length);
	content.endElement ("", "", name);
    }

    public void channelUpdate (RssChannel channel)
    throws SAXException
    {
	AttributesImpl		atts = new AttributesImpl ();

	content.startDocument ();
	if (lexical != null) {
	    lexical.startDTD ("rss",
		"-//Netscape Communications//DTD RSS 0.91//EN",
 		"http://my.netscape.com/publish/formats/rss-0.91.dtd");
	    lexical.endDTD ();
	}

	atts.addAttribute ("", "", "version", "CDATA", "0.91");
	content.startElement ("", "", "rss", atts);
	atts.clear ();
	doIndent (0);
	content.startElement ("", "", "channel", atts);

	// describe the channel
	// four required elements
	element (1, "title", channel.title, atts);
	element (1, "link", channel.link, atts);
	element (1, "description", channel.description, atts);
	element (1, "language", channel.language, atts);

	// optional elements
	if ("" != channel.managingEditor)
	    element (1, "managingEditor", channel.managingEditor, atts);
	if ("" != channel.webMaster)
	    element (1, "webMaster", channel.webMaster, atts);
	// ... and many others, notably image/icon and text input


	// channel contents: at least one item
	for (Enumeration e = channel.items.elements ();
		e.hasMoreElements ();
		/**/) {
	    RssItem	item = (RssItem) e.nextElement ();
	    doIndent (1);
	    content.startElement ("", "", "item", atts);
	    if ("" != item.title)
		element (2, "title", item.title, atts);
	    if ("" != item.link)
		element (2, "link", item.link, atts);
	    if ("" != item.description)
		element (2, "description", item.description, atts);
	    doIndent (1);
	    content.endElement ("", "", "item");
	}

	content.endElement ("", "", "channel");
	content.endElement ("", "", "rss");
	content.endDocument ();
    }
}