package apexample.view;

import apexample.model.*;

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

/**
 * A custom tag class for the RSSItems tag.  Iterates through each item in
 * the RSS channel, exposing the name and link of each item 
 * as scripting variables
 */
public class RSSItemsTag extends BodyTagSupport implements IterationTag {
    /** the names of the scripting variables */
    private static final String NAME_ATTR = "itemName";
    private static final String LINK_ATTR = "itemLink";
    
    /** the index of the current item in the channel */
    private int counter;
    
    /** the RSS parser */
    private RSSInfo rssInfo;
    
    /**
     * Constructor
     */
    public RSSItemsTag() {
        super();   
        counter = 0;
    }
    
    /**
     * Find the RSS parser in the parent tag and set the intial value of
     * the scripting variables.
     */
    public int doStartTag() throws JspException {
        if (rssInfo == null) {
            RSSChannelTag rct = 
                (RSSChannelTag)findAncestorWithClass(this, RSSChannelTag.class);
           rssInfo = rct.getRSSInfo();
        }
        
        pageContext.setAttribute(NAME_ATTR, rssInfo.getTitleAt(counter));
        pageContext.setAttribute(LINK_ATTR, rssInfo.getLinkAt(counter));
        return Tag.EVAL_BODY_INCLUDE;
    }
 
    /**
     * After each pass, iterate the counter.  If there are still any items
     * left, set the scripting variables
     */
    public int doAfterBody() throws JspException {
        if (++counter >= rssInfo.getItemCount()) {
            return IterationTag.SKIP_BODY;
        } else {     
            pageContext.setAttribute(NAME_ATTR, rssInfo.getTitleAt(counter));
            pageContext.setAttribute(LINK_ATTR, rssInfo.getLinkAt(counter));
            return IterationTag.EVAL_BODY_AGAIN;
        }
    }
}