/*
 * Copyright 2006 The Apache Software Foundation.
 * 
 * Licensed under the Apache 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.apache.org/licenses/LICENSE-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.apache.shale.dialog.faces;

import javax.faces.application.NavigationHandler;
import javax.faces.application.ViewHandler;
import javax.faces.context.FacesContext;
import javax.faces.event.PhaseEvent;
import javax.faces.event.PhaseId;
import javax.faces.event.PhaseListener;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * <p>A JavaServer Faces <code>PhaseListener</code> that provides support for
 * <code>DialogNavigationHandler</code> facility of Shale. This <code>PhaseListener</code>
 * allows you to hook up the <i>DialogManager</i> without invoking on an <code>UICommand</code>
 * class inside of your JSF page. For instance, when you are using <code>j_security</code> and willing
 * to forward to a <code>Dialog</code>.</p>
 * 
 * <p>To use this <code>PhaseListener</code> configure it inside your <code>faces-config.xml</code>.
 * Create a JavaServer Page, containing the <code>jsp:forward</code>-Tag. For the <code>page</code>
 * attribute value use something like <code>initdialog/dialog.faces</code>, where <code>dialog</code> is 
 * the name of your <code>Dialog</code>, you'd like to invoke.</p>
 * 
 * <p>The benefit is you can process the standard Request Processing Lifecycle, without requiring explicit
 * configuration (for example, of a Servlet or a Filter).</p>
 */
public class InitDialogPhaseListener  implements PhaseListener {

    private transient Log log = LogFactory.getLog(InitDialogPhaseListener.class);
	
	/**
	 * constant, which this <code>PhaseListner</code> intercepts.
	 */
    public static String INIT_DIALOG = "/initdialog";

	private static final long serialVersionUID = 1L;

    //	 --------------------------------------------------- PhaseListener Methods
	
    /**
     * <p>Perform interception processing activities <em>after</em> the
     * specified phase processing has been performed.</p>
     *
     * @param event <code>PhaseEvent</code> to be processed
     */
	public void afterPhase(PhaseEvent event) {
		FacesContext facesContext = event.getFacesContext();
		if(facesContext.getViewRoot().getViewId().startsWith(INIT_DIALOG))
			invokeApplication(facesContext);
	}
	
    /**
     * <p>Perform interception processing activities <em>before</em> the
     * specified phase processing has been performed.</p>
     *
     * @param event <code>PhaseEvent</code> to be processed
     */
	public void beforePhase(PhaseEvent event) {
	}

    /**
     * <p>Return the identifier of the JavaServer Faces request processing
     * lifecycle phase(s) that we are interested in.</p>
     */
	public PhaseId getPhaseId() {
		
		return PhaseId.RESTORE_VIEW;
	}

	
    // --------------------------------------------------------- Support Methods	

	/**
     * <p>This method handles the invocation of the <code>DialogNavigationHandler</code>
     * of Shale, by the given ViewId.</p>
	 * 
	 * @param facesContext <code>FacesContext</code> for the current request
	 */
	private void invokeApplication(FacesContext facesContext) {
		String incommingViewId = facesContext.getViewRoot().getViewId();
		if(log.isTraceEnabled())
			log.trace("Incomming view id: " + incommingViewId);
		String viewId = incommingViewId.substring(INIT_DIALOG.length());
		facesContext.getViewRoot().setViewId(viewId);
		if(log.isTraceEnabled())
			log.trace("new generated view id: " + viewId);
		
		String dialog = extractDialogName(viewId);
		
		NavigationHandler navigationHandler = facesContext.getApplication().getNavigationHandler();
		if (navigationHandler instanceof DialogNavigationHandler) { 
			navigationHandler.handleNavigation(facesContext, null, DialogNavigationHandler.PREFIX+dialog);
		} else {
			if(log.isFatalEnabled())
				log.fatal(navigationHandler + " is not instanceof " + DialogNavigationHandler.class);
			 facesContext.renderResponse();

		 }
		
	}

	/**
	 * Helper method to extract the name of the desired <code>Dialog</code> from the
	 * given ViewId.
	 * @param viewId the given ViewId for the request, we are processing
	 * @return name of the <code>Dialog</code>
	 */
	private String extractDialogName(String viewId) {
		String extract = viewId.substring(1);
		extract = extract.substring(0,extract.indexOf(ViewHandler.DEFAULT_SUFFIX));
		return extract;
	}
}