/*
 * $Id: TilesUtilImpl.java 471754 2006-11-06 14:55:09Z husted $
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.struts.tiles;

import java.io.IOException;
import java.io.Serializable;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.PageContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.tiles.definition.ComponentDefinitionsFactoryWrapper;
import org.apache.struts.util.RequestUtils;

/**
 * Default implementation of TilesUtil.
 * This class contains default implementation of utilities. This implementation
 * is intended to be used without Struts.
 */
public class TilesUtilImpl implements Serializable {

    /** Commons Logging instance.*/
    protected static final Log log = LogFactory.getLog(TilesUtil.class);

    /** Constant name used to store factory in servlet context */
    public static final String DEFINITIONS_FACTORY =
        "org.apache.struts.tiles.DEFINITIONS_FACTORY";

    /**
     * JSP 2.0 include method to use which supports configurable flushing.
     */
    private static Method include = null;

    /**
     * Initialize the include variable with the
     * JSP 2.0 method if available.
     */
    static {

        try {
            // get version of include method with flush argument
            Class[] args = new Class[]{String.class, boolean.class};
            include = PageContext.class.getMethod("include", args);
        } catch (NoSuchMethodException e) {
            log.debug("Could not find JSP 2.0 include method.  Using old one that doesn't support " +
                      "configurable flushing.", e);
        }
    }

    /**
     * Do a forward using request dispatcher.
     *
     * This method is used by the Tiles package anytime a forward is required.
     * @param uri Uri or Definition name to forward.
     * @param request Current page request.
     * @param servletContext Current servlet context.
     */
    public void doForward(
        String uri,
        HttpServletRequest request,
        HttpServletResponse response,
        ServletContext servletContext)
        throws IOException, ServletException {

        request.getRequestDispatcher(uri).forward(request, response);
    }

    /**
     * Do an include using request dispatcher.
     *
     * This method is used by the Tiles package when an include is required.
     * The Tiles package can use indifferently any form of this method.
     * @param uri Uri or Definition name to forward.
     * @param request Current page request.
     * @param response Current page response.
     * @param servletContext Current servlet context.
     */
    public void doInclude(
        String uri,
        HttpServletRequest request,
        HttpServletResponse response,
        ServletContext servletContext)
        throws IOException, ServletException {

        request.getRequestDispatcher(uri).include(request, response);
    }

    /**
     * Do an include using PageContext.include().
     *
     * This method is used by the Tiles package when an include is required.
     * The Tiles package can use indifferently any form of this method.
     * @param uri Uri or Definition name to forward.
     * @param pageContext Current page context.
     * @param flush If the writer should be flushed before the include
     */
    public void doInclude(String uri, PageContext pageContext, boolean flush)
        throws IOException, ServletException {
        try {
            // perform include with new JSP 2.0 method that supports flushing
            if (include != null) {
                include.invoke(pageContext, new Object[]{uri, Boolean.valueOf(flush)});
                return;
            }
        } catch (IllegalAccessException e) {
            log.debug("Could not find JSP 2.0 include method.  Using old one.", e);
        } catch (InvocationTargetException e) {
            log.debug("Unable to execute JSP 2.0 include method.  Trying old one.", e);
        }

        pageContext.include(uri);
    }

    /**
     * Get definition factory from appropriate servlet context.
     * @return Definitions factory or <code>null</code> if not found.
     */
    public DefinitionsFactory getDefinitionsFactory(
        ServletRequest request,
        ServletContext servletContext) {

        return (DefinitionsFactory) servletContext.getAttribute(DEFINITIONS_FACTORY);
    }

    /**
     * Create Definition factory from specified configuration object.
     * Create an instance of the factory with the class specified in the config
     * object. Then, initialize this factory and finally store the factory in
     * appropriate context by calling
     * {@link #makeDefinitionsFactoryAccessible(DefinitionsFactory, ServletContext)}.
     * Factory creation is done by {@link #createDefinitionFactoryInstance(String)}.
     * <p>
     *
     * @param servletContext Servlet Context passed to newly created factory.
     * @param factoryConfig Configuration object passed to factory.
     * @return newly created factory of type specified in the config object.
     * @throws DefinitionsFactoryException If an error occur while initializing factory
     */
    public DefinitionsFactory createDefinitionsFactory(
        ServletContext servletContext,
        DefinitionsFactoryConfig factoryConfig)
        throws DefinitionsFactoryException {

        // Create configurable factory
        DefinitionsFactory factory =
            createDefinitionFactoryInstance(factoryConfig.getFactoryClassname());

        factory.init(factoryConfig, servletContext);

        // Make factory accessible from jsp tags (push it in appropriate context)
        makeDefinitionsFactoryAccessible(factory, servletContext);
        return factory;
    }

    /**
     * Create Definition factory of specified classname.
     * Factory class must extend the {@link DefinitionsFactory} class.
     * The factory is wrapped appropriately with {@link ComponentDefinitionsFactoryWrapper}
     * if it is an instance of the deprecated ComponentDefinitionsFactory class.
     * @param classname Class name of the factory to create.
     * @return newly created factory.
     * @throws DefinitionsFactoryException If an error occur while initializing factory
     */
    protected DefinitionsFactory createDefinitionFactoryInstance(String classname)
        throws DefinitionsFactoryException {

        try {
            Class factoryClass = RequestUtils.applicationClass(classname);
            Object factory = factoryClass.newInstance();

            // Backward compatibility : if factory classes implements old interface,
            // provide appropriate wrapper
            if (factory instanceof ComponentDefinitionsFactory) {
                factory =
                    new ComponentDefinitionsFactoryWrapper(
                        (ComponentDefinitionsFactory) factory);
            }
            return (DefinitionsFactory) factory;

        } catch (ClassCastException ex) { // Bad classname
            throw new DefinitionsFactoryException(
                "Error - createDefinitionsFactory : Factory class '"
                    + classname
                    + " must implement 'TilesDefinitionsFactory'.",
                ex);

        } catch (ClassNotFoundException ex) { // Bad classname
            throw new DefinitionsFactoryException(
                "Error - createDefinitionsFactory : Bad class name '"
                    + classname
                    + "'.",
                ex);

        } catch (InstantiationException ex) { // Bad constructor or error
            throw new DefinitionsFactoryException(ex);

        } catch (IllegalAccessException ex) {
            throw new DefinitionsFactoryException(ex);
        }
    }

    /**
     * Make definition factory accessible to Tags.
     * Factory is stored in servlet context.
     * @param factory Factory to be made accessible.
     * @param servletContext Current servlet context.
     */
    protected void makeDefinitionsFactoryAccessible(
        DefinitionsFactory factory,
        ServletContext servletContext) {

        servletContext.setAttribute(DEFINITIONS_FACTORY, factory);
    }

}