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/*
 * 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 io.milton.servlet;

import io.milton.http.HttpManager;
import io.milton.http.Request;
import io.milton.http.Response;
import java.io.IOException;

import jakarta.servlet.Servlet;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


/**
 * 
 * MiltonServlet is a thin wrapper around HttpManager. It takes care of initialisation
 * and delegates requests to the HttpManager
 * 
 * The servlet API is hidden by the Milton API, however you can get access to
 * the underlying request and response objects from the static request and response
 * methods which use ThreadLocal variables
 *
 * This spring aware servlet will load the spring context from a classpath
 * resource named /applicationContext.xml
 *
 * It will then load a bean named milton.http.manager which must be of type
 * HttpManager.
 *
 * An example applicationContext.xml might look like this
 *
 *  * {@code
 * 
 *
 *   
 *       
 *       
 *   
 *
 *   
 *       
 *   
 *
 *   
 *
 *   
 *       
 *       
 *   
 * 
 * }
 * 
 * @author brad
 */
public class SpringAwareMiltonServlet implements Servlet{
    
    private final Logger log = LoggerFactory.getLogger(SpringAwareMiltonServlet.class);
    
    ServletConfig config;
    ApplicationContext context;
    HttpManager httpManager;
    
    private ServletContext servletContext;
    
    private static final ThreadLocal originalRequest = new ThreadLocal<>();
    private static final ThreadLocal originalResponse = new ThreadLocal<>();

    public static HttpServletRequest request() {
        return originalRequest.get();
    }
    
    public static HttpServletResponse response() {
        return originalResponse.get();
    }
    
    public static void forward(String url) {
        try {
            request().getRequestDispatcher(url).forward(originalRequest.get(),originalResponse.get());
        } catch (IOException | ServletException ex) {
            throw new RuntimeException(ex);
        }
    }
    
    @Override
    public void init(ServletConfig config) throws ServletException {
        try {
            this.config = config;
            servletContext = config.getServletContext();
            context = new ClassPathXmlApplicationContext(new String[] {"applicationContext.xml"});
            httpManager = (HttpManager) context.getBean("milton.http.manager");
        } catch (Throwable ex) {
            log.error("Exception starting milton servlet",ex);
            throw new RuntimeException(ex);
        }        
    }
    
    @Override
    public void service(jakarta.servlet.ServletRequest servletRequest, jakarta.servlet.ServletResponse servletResponse) throws ServletException, IOException {
        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;
        try {
            originalRequest.set(req);
            originalResponse.set(resp);
            Request request = new ServletRequest(req, servletContext);
            Response response = new ServletResponse(resp);
            httpManager.process(request, response);
        } finally {
            originalRequest.remove();
            originalResponse.remove();
            ServletRequest.clearThreadLocals();
            servletResponse.getOutputStream().flush();            
            servletResponse.flushBuffer();
        }
    }

    @Override
    public String getServletInfo() {
        return "SpringAwareMiltonServlet";
    }

    @Override
    public ServletConfig getServletConfig() {
        return config;
    }

    @Override
    public void destroy() {
        
    }
}