package com.atlassian.refapp.sal;
   
   import javax.servlet.http.HttpServletRequest;
   
   /**
    * Utility class for extracting the base URL (scheme, hostname, port, and context path) from an {@link
    * HttpServletRequest}.
    *
    * @since 2.0.8
   */
  final class HttpServletRequestBaseUrlExtractor {
      private HttpServletRequestBaseUrlExtractor() {
          throw new AssertionError("may not be constructed");
      }
  
      /**
       * Extract the base URL from the specified request.
       *
       * @param request the current {@code HttpServletRequest}.  Must not be {@code null} or a {@code
       *                NullPointerException} will be thrown.
       * @return a string representation of the base URL of the current request
       * @throws NullPointerException if {@code request} is {@code null}
       */
      static String extractBaseUrl(HttpServletRequest request) {
          if (request == null) {
              throw new NullPointerException("request parameter must not be null");
          }
          StringBuilder baseUrl = new StringBuilder(request.getScheme());
          baseUrl.append("://").append(request.getServerName());
          if (!isDefaultPort(request.getScheme(), request.getServerPort())) {
              baseUrl.append(":").append(request.getServerPort());
          }
          baseUrl.append(request.getContextPath());
          return baseUrl.toString();
      }
  
      private static boolean isDefaultPort(String scheme, int serverPort) {
          return (scheme.equals("http") && serverPort == 80) || (scheme.equals("https") && serverPort == 443);
      }
  }