MoreLink.java

package com.wooki.components;

import org.apache.tapestry5.BindingConstants;
import org.apache.tapestry5.ComponentEventCallback;
import org.apache.tapestry5.ComponentResources;
import org.apache.tapestry5.EventConstants;
import org.apache.tapestry5.Link;
import org.apache.tapestry5.MarkupWriter;
import org.apache.tapestry5.annotations.AfterRender;
import org.apache.tapestry5.annotations.BeginRender;
import org.apache.tapestry5.annotations.OnEvent;
import org.apache.tapestry5.annotations.Parameter;
import org.apache.tapestry5.corelib.base.AbstractLink;
import org.apache.tapestry5.internal.services.PageRenderQueue;
import org.apache.tapestry5.internal.util.Holder;
import org.apache.tapestry5.ioc.annotations.Inject;
import org.apache.tapestry5.ioc.services.TypeCoercer;
import org.apache.tapestry5.json.JSONObject;
import org.apache.tapestry5.services.PartialMarkupRenderer;
import org.apache.tapestry5.services.PartialMarkupRendererFilter;
import org.apache.tapestry5.services.javascript.JavaScriptSupport;

import com.wooki.AppendPosition;
import com.wooki.MoreEventResult;
import com.wooki.WookiEventConstants;

/**
 * This link will be used to append information to a zone. The position can be on top or at the
 * bottom of the HTML element associated to the link.
 * 
 * @author ccordenier
 */
public class MoreLink extends AbstractLink
{

    /**
     * Specify the first page index.
     */
    @Parameter
    private int first;

    /**
     * The name of the element to update.
     */
    @Parameter(defaultPrefix = BindingConstants.LITERAL)
    private String zone;

    /**
     * Where should the content be append : top or botttom
     */
    @Parameter(defaultPrefix = BindingConstants.LITERAL, value = "bottom")
    private AppendPosition position;

    /**
     * The class of the element that shows the ajax loader image
     */
    @Parameter(value = "load-more", defaultPrefix = BindingConstants.LITERAL)
    private String loaderClass;

    @Inject
    private ComponentResources resources;

    @Inject
    private JavaScriptSupport renderSupport;

    @Inject
    private TypeCoercer typeCoercer;

    @Inject
    private PageRenderQueue pageRenderQueue;

    private String loader;

    @BeginRender
    void initMoreLink(MarkupWriter writer)
    {
        if (isDisabled()) return;

        Link link = resources.createEventLink(EventConstants.ACTION, first);
        writer.element("div", "class", "more-link radied");
        writeLink(writer, link);

        loader = renderSupport.allocateClientId("loader");

        JSONObject data = new JSONObject();
        data.put("elt", this.getClientId());
        data.put("position", this.position.toString());
        data.put("zone", this.zone);
        data.put("loader", loader);
        data.put("url", link.toURI());
        renderSupport.addInitializerCall("initMoreLink", data);
    }

    @AfterRender
    void afterRender(MarkupWriter writer)
    {
        if (isDisabled()) return;
        writer.end(); // <a>

        writer.element("div", "id", loader, "class", this.loaderClass, "style", "display:none;");
        writer.end(); // <div> loader

        writer.end(); // <div>
    }

    /**
     * When more is used via Javascript, href attribute is update via this method.
     * 
     * @return the object to render.
     */
    @SuppressWarnings("unchecked")
    @OnEvent(value = EventConstants.ACTION)
    public Object updateContext(final int page)
    {

        // Get the new context
        final Holder<MoreEventResult> holder = Holder.create();
        ComponentEventCallback callback = new ComponentEventCallback()
        {
            public boolean handleResult(Object result)
            {
                if (result == null) { return true; }
                holder.put(typeCoercer.coerce(result, MoreEventResult.class));
                return true;
            }
        };

        resources.triggerEvent(WookiEventConstants.UPDATE_MORE_CONTEXT, new Object[]
        { page }, callback);

        // Add results in JSON reply
        pageRenderQueue.addPartialMarkupRendererFilter(new PartialMarkupRendererFilter()
        {

            public void renderMarkup(MarkupWriter writer, JSONObject reply,
                    PartialMarkupRenderer renderer)
            {
                if (holder.hasValue())
                {
                    Link link = resources.createEventLink(EventConstants.ACTION, page + 1);
                    reply.put("href", link.toURI());
                    reply.put("hasMore", holder.get().hasMore());
                }
                else
                {
                    reply.put("empty", true);
                }
                renderer.renderMarkup(writer, reply);
            }
        });

        // Check if there is more data to render
        if (holder.hasValue()) { return holder.get().getRenderable(); }

        return null;
    }

}