level 1 uri parser

gistfile1.txt

   /**
    * 
    * @param template
    *           URI string that can be in level 1 <a href="http://tools.ietf.org/html/rfc6570">RFC6570</a> form.
    * 
    * @param variables
    *           to the URI string
    * @throws IllegalArgumentException
    *            if there's a problem in the input data
    */
   public static String expand(String template, Map<String, ?> variables) {
      if (template.length() < 3) // skip expansion if there's no valid variables set. ex. {a} is the first valid
         return template.toString();

      boolean inVar = false;
      char last = '|';// dummy initializer; only concerned with slashes
      StringBuilder var = new StringBuilder();
      StringBuilder builder = new StringBuilder();
      for (char c : Lists.charactersOf(template)) {
         switch (c) {
         case '{':
            inVar = true;
            break;
         case '}':
            inVar = false;
            String key = var.toString();
            Object value = variables.get(var.toString());
            checkArgument(value != null, "unresolved template parameter %s in %s", key, template);
            builder.append(value);
            var = new StringBuilder();
            break;
         case '/':
            if (last == '/')
               break; // make sure we don't do double-slashing in the path
         default:
            if (inVar)
               var.append(c);
            else
               builder.append(c);
         }
         last = c;
      }
      return builder.toString();
   }