package vhexample.view;

import javax.servlet.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;

/**
 * A custom tag for the RSS channel.  Exposes two scripting variables
 * for channel name and link.  Also used by nested item tags to 
 * find the information for each item in the channel
 */
public class RSSChannelTag extends BodyTagSupport {
    /** the names of the scripting variable */
    private static final String NAME_ATTR = "channelName";
    private static final String LINK_ATTR = "channelLink";
    
    /** the url of the RSS page */
    private String url;
    
    /** the RSS parser */
    private RSSInfo rssInfo;
    
    /**
     * Constructor 
     */
    public RSSChannelTag() {
        rssInfo = new RSSInfo();
    }
    
    /**
     * Called with the URL attribute of the tag
     */
    public void setURL(String url) {
        this.url = url;
    }
    
    /**
     * Called by nested tags to get the RSS parser
     */
    protected RSSInfo getRSSInfo() {
        return rssInfo;
    }
    
    /**
     * Parse the RSS and set the scripting variables
     */
    public int doStartTag() throws JspException {
        try {
            // parse the rss
            rssInfo.parse(url);
            
            // export the scripting variables
            pageContext.setAttribute(NAME_ATTR, rssInfo.getChannelTitle());
            pageContext.setAttribute(LINK_ATTR, rssInfo.getChannelLink());
        } catch (Exception ex) {
            throw new JspException("Unable to parse " + url, ex);
        }
        
        return Tag.EVAL_BODY_INCLUDE;
    }
}