/**
    * This file Copyright (c) 2010-2018 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.cms.util;
  
  import java.io.IOException;
  import java.net.MalformedURLException;
  import java.net.URL;
  
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.commons.lang3.ClassUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.http.HttpEntity;
  import org.apache.http.client.methods.CloseableHttpResponse;
  import org.apache.http.client.methods.HttpGet;
  import org.apache.http.impl.client.CloseableHttpClient;
  import org.apache.http.impl.client.HttpClients;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Provides support for a simple syntax form of doing redirects and forwards. You pass it a url prefixed with either
   * "redirect:", "permanent:", "forward:" or "proxy:". The context path is added to the url.
   */
  public class RequestDispatchUtil {
  
      private static final Logger log = LoggerFactory.getLogger(RequestDispatchUtil.class);
  
      public static final String REDIRECT_PREFIX = "redirect:";
      public static final String PERMANENT_PREFIX = "permanent:";
      public static final String FORWARD_PREFIX = "forward:";
      public static final String PROXY_PREFIX = "proxy:";
  
      /**
       * Returns true if processing took place, even if it fails.
       */
      public static boolean dispatch(String targetUri, HttpServletRequest request, HttpServletResponse response) {
  
          if (targetUri == null) {
              return false;
          }
  
          if (targetUri.startsWith(REDIRECT_PREFIX)) {
              String redirectUrl = StringUtils.substringAfter(targetUri, REDIRECT_PREFIX);
              try {
  
                  if (isInternal(redirectUrl) && !StringUtils.startsWith(redirectUrl, request.getContextPath())) {
                      redirectUrl = request.getContextPath() + redirectUrl;
                  }
  
                  response.sendRedirect(response.encodeRedirectURL(redirectUrl));
  
              } catch (IOException e) {
                  log.error("Failed to redirect to {}:{}", targetUri, e.getMessage());
              }
              return true;
          }
  
          if (targetUri.startsWith(PERMANENT_PREFIX)) {
              String permanentUrl = StringUtils.substringAfter(targetUri, PERMANENT_PREFIX);
              try {
  
                  if (isInternal(permanentUrl)) {
                      if (isUsingStandardPort(request)) {
                          permanentUrl = new URL(
                                  request.getScheme(),
                                  request.getServerName(),
                                 request.getContextPath() + permanentUrl).toExternalForm();
                     } else {
                         permanentUrl = new URL(
                                 request.getScheme(),
                                 request.getServerName(),
                                 request.getServerPort(),
                                 request.getContextPath() + permanentUrl).toExternalForm();
                     }
                 }
 
                 response.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
                 response.setHeader("Location", permanentUrl);
 
             } catch (MalformedURLException e) {
                 log.error("Failed to create permanent url to redirect to {}:{}", targetUri, e.getMessage());
             }
             return true;
         }
 
         if (targetUri.startsWith(FORWARD_PREFIX)) {
             String forwardUrl = StringUtils.substringAfter(targetUri, FORWARD_PREFIX);
             try {
                 request.getRequestDispatcher(forwardUrl).forward(request, response);
             } catch (Exception e) {
                 log.error("Failed to forward to {} - {}:{}", forwardUrl, ClassUtils.getShortClassName(e.getClass()), e.getMessage());
             }
             return true;
         }
 
         if (targetUri.startsWith(PROXY_PREFIX)) {
             String forwardUrl = StringUtils.substringAfter(targetUri, PROXY_PREFIX);
             forwardToExternalURL(response, forwardUrl);
             return true;
         }
 
         return false;
     }
 
     private static void forwardToExternalURL(HttpServletResponse response, String forwardUrl) {
         CloseableHttpClient httpClient = HttpClients.createDefault();
 
         try {
             HttpGet req = new HttpGet(forwardUrl);
 
             CloseableHttpResponse resp = httpClient.execute(req);
             try {
                 HttpEntity entity = resp.getEntity();
                 response.setStatus(resp.getStatusLine().getStatusCode());
                 if (entity != null) {
                     response.setContentType(entity.getContentType().getValue());
                     entity.writeTo(response.getOutputStream());
                 }
             } finally {
                 resp.close();
             }
         } catch (Exception e) {
             log.error("Failed to forward to  external URL {} - {}:{}", forwardUrl, ClassUtils.getShortClassName(e.getClass()), e.getMessage());
         } finally {
             try {
                 httpClient.close();
             } catch (IOException e) {
             }
         }
     }
 
     private static boolean isUsingStandardPort(HttpServletRequest request) {
         String requestScheme = request.getScheme();
         int serverPort = request.getServerPort();
         return (serverPort == 80 && "http".equals(requestScheme)) || (serverPort == 443 && "https".equals(requestScheme));
     }
 
     private static boolean isInternal(String url) {
         return !url.startsWith("http://") && !url.startsWith("https://");
     }
 }