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/**********************************************************************************
 * $URL$
 * $Id$
 ***********************************************************************************
 *
 * Copyright (c) 2003, 2004, 2005, 2006, 2008 The Sakai Foundation
 *
 * Licensed under the Educational Community License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.opensource.org/licenses/ECL-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 **********************************************************************************/

package org.sakaiproject.vm;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.sakaiproject.util.Web;

/**
 * 
 * VmServlet is a Servlet that makes use of the Velocity Template Engine.
 * 
 * 
 * This extends our ComponentServlet, giving us also the ability to find registered service components.
 * 
 */
public abstract class VmServlet extends ComponentServlet
{
	/**
	 * Access the object set in the velocity context for this name, if any.
	 * 
	 * @param name
	 *        The reference name.
	 * @param request
	 *        The request.
	 * @return The reference value object, or null if none
	 */
	public Object getVmReference(String name, HttpServletRequest request)
	{
		return request.getAttribute(name);
	}

	/**
	 * Add a reference object to the velocity context by name - if it's not already defined
	 * 
	 * @param name
	 *        The reference name.
	 * @param value
	 *        The reference value object.
	 * @param request
	 *        The request.
	 */
	public void setVmReference(String name, Object value, HttpServletRequest request)
	{
		if (request.getAttribute(name) == null)
		{
			request.setAttribute(name, value);
		}
		// else
		// {
		// Object old = request.getAttribute(name);
		// if (!old.equals(value))
		// {
		// log("double setting vmReference: " + name + " was: " + old + " to: " + value);
		// }
		// }
	}

	/**
	 * Add some standard references to the vm context.
	 * 
	 * @param request
	 *        The request.
	 * @param response
	 *        The response.
	 */
	protected void setVmStdRef(HttpServletRequest request, HttpServletResponse response)
	{
		// include some standard references
		setVmReference("sakai_ActionURL", getActionURL(request), request);

		// get the include (from the portal) for the HTML HEAD
		if (getVmReference("sakai_head", request) == null)
		{
			String headInclude = (String) request.getAttribute("sakai.html.head");
			if (headInclude != null)
			{
				setVmReference("sakai_head", headInclude, request);
			}
		}

		// get the include (from the portal) for the HTML BODY onload
		if (getVmReference("sakai_onload", request) == null)
		{
			String onload = (String) request.getAttribute("sakai.html.body.onload");
			if (onload != null)
			{
				setVmReference("sakai_onload", onload, request);
			}
		}

		// get the include (from the portal) for the HTML BODY onload
		if (getVmReference("sakai_class", request) == null)
		{
			String className = (String) request.getAttribute("sakai.html.body.class");
			if (className != null)
			{
				setVmReference("sakai_class", className, request);
			}
		}

		// set the ref to the images
		if (getVmReference("sakai_image_path", request) == null)
		{
			setVmReference("sakai_image_path", "/library/image/", request);
		}

		// set the ref to the javscripts
		if (getVmReference("sakai_script_path", request) == null)
		{
			setVmReference("sakai_script_path", "/library/js/", request);
		}

		// set the ref to the library
		if (getVmReference("sakai_library_path", request) == null)
		{
			setVmReference("sakai_library_path", "/library/", request);
		}

	}

	/**
	 * Include the Velocity template, expanded with the current set of references
	 * 
	 * @param template
	 *        The path, relative to the webapp context, of the template file
	 * @param request
	 *        The render request.
	 * @param response
	 *        The render response.
	 * @throws PortletException
	 *         if something goes wrong.
	 */
	protected void includeVm(String template, HttpServletRequest request, HttpServletResponse response) throws ServletException
	{
		// include some standard references
		setVmStdRef(request, response);

		response.setContentType("text/html");

		// tell our vm processor to use this template
		request.setAttribute("sakai.vm.path", template);

		try
		{
			// get the vm by name so it does not have to have a URL mapping
			RequestDispatcher dispatcher = getServletContext().getNamedDispatcher("sakai.vm");
			dispatcher.include(request, response);
		}
		catch (IOException e)
		{
			throw new ServletException("includeVm: template: " + template, e);
		}
	}

	/**
	 * Get a new ActionURL.
	 * 
	 * @param req
	 *        The current request.
	 * @return A new ActionURL.
	 */
	protected ActionURL getActionURL(HttpServletRequest request)
	{
		ActionURL a = new ActionURL(Web.returnUrl(request, null), request);

		// set the pid and panel, if present in the request
		// a.setPid(request.getParameter(ActionURL.PARAM_PID));
		a.setPanel(request.getParameter(ActionURL.PARAM_PANEL));
		a.setSite(request.getParameter(ActionURL.PARAM_SITE));
		a.setPage(request.getParameter(ActionURL.PARAM_PAGE));

		return a;
	}
}