/*

  * $Source$

  * $Revision$

  *

  * Copyright (C) 2001 Myles Chippendale

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) the GNU General Public License as published by the Free Software

  *    Foundation; either version 2 of the License, or (at your option)

  *    any later version,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * Contact details for copyright holder:

  *

  *     Myles Chippendale <mylesc At paneris.org>

  */

 package org.melati.util;

 import javax.servlet.http.HttpServletRequest;

 /**

  * An assortment of useful things to do with <code>Http</code>.

  */

 public final class HttpUtil {

   private HttpUtil() {}

   /**

    * Add a Zone URL to buffer.

    *  

    * @param url an empty StringBuffer to append to 

    * @param request the request to interrogate

    */

   public static void appendZoneURL(StringBuffer url, 

                                    HttpServletRequest request) {

     String scheme = request.getScheme();

     url.append(scheme);

     url.append("://");

     url.append(request.getServerName());

     if ((scheme.equals("http") && 

         request.getServerPort() != 80

         )

         ||

         (scheme.equals("https") && 

         request.getServerPort() != 443)) {

       url.append(':');

       url.append(request.getServerPort());

     }

     appendRelativeZoneURL(url,request);

   }

   /**

    * Return the server URL.

    *  

    * @param request the request to interrogate

    */

   public static String getServerURL(HttpServletRequest request) {

     StringBuffer url = new StringBuffer();

     String scheme = request.getScheme();

     url.append(scheme);

     url.append("://");

     url.append(request.getServerName());

     if ((scheme.equals("http") && 

         request.getServerPort() != 80

         )

         ||

         (scheme.equals("https") && 

         request.getServerPort() != 443)) {

       url.append(':');

       url.append(request.getServerPort());

     }

     return url.toString();

   }

   /**

    * Append relative servlet zone url.

    * 

    * Note that this function should return 

    * /zone/servlet from a request of form 

    * http://host/zone/servlet/pathinfo?querystring

    * on all servlet API versions greater than 2.0.

    * In 2.0 the zone was returned in the ServletPath 

    * it is now in the ContextPath.

    * @param url StringBuffer to append to 

    * @param request the request to interrogate

    */

   public static void appendRelativeZoneURL (

       StringBuffer url, HttpServletRequest request) {

     url.append(request.getContextPath());

     String servletPath = request.getServletPath();

     if (servletPath != null && !servletPath.equals("")) {

       url.append(servletPath.substring(0, servletPath.lastIndexOf('/')));

       if (servletPath.lastIndexOf('/') == -1) 

         throw new MelatiBugMelatiException(

             "Servlet Path does not contain a forward slash:" + servletPath);

     }

   }

   /**

    * Retrieve a Zone url.

    * @param request the request to interrogate

    * @return an Url up to the zone specification as a String 

    */

   public static String zoneURL(HttpServletRequest request) {

     StringBuffer url = new StringBuffer();

     appendZoneURL(url, request);

     return url.toString();

   }

   /**

    * Retrieve a Servlet url from a request.

    * @param request the request to interrogate

    * @return an Url up to the servlet specification as a String 

    */

   public static String servletURL(HttpServletRequest request) {

     StringBuffer url = new StringBuffer();

     appendZoneURL(url, request);

     String servlet = request.getServletPath();

     if (servlet != null && !servlet.equals(""))

       url.append(servlet.substring(

                           servlet.lastIndexOf('/'), servlet.length()));

     return url.toString();

   }

   /**

    * Retrieve a relative url from a request.

    * @param request the request to interrogate

    * @return a relative Url  

    */

   public static String getRelativeRequestURL(HttpServletRequest request) {

     StringBuffer url = new StringBuffer();

     url.append(request.getContextPath());

     if (request.getServletPath() != null) url.append(request.getServletPath());

     if (request.getPathInfo() != null) url.append(request.getPathInfo());

     return url.toString();

   }

   /**

    * @param url An url or relative url which may end in a slash

    * @param relativeUrl A relative url which may start with a slash

    * @return an url without a duplicated slash at the join

    */

   public static String concatenateUrls(String url, String relativeUrl) {

     if (url.endsWith("/") && relativeUrl.startsWith("/"))

       return url.substring(0, url.lastIndexOf('/')) + relativeUrl;

     else 

       return url + relativeUrl;

   }

 }