content: /*
   * 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 org.apache.activemq.transport.amqp.message;
  
  import java.nio.charset.Charset;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.charset.StandardCharsets;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.StringTokenizer;
  
  public final class AmqpContentTypeSupport {
  
      private static final String UTF_8 = "UTF-8";
      private static final String CHARSET = "charset";
      private static final String TEXT = "text";
      private static final String APPLICATION = "application";
      private static final String JAVASCRIPT = "javascript";
      private static final String XML = "xml";
      private static final String XML_VARIANT = "+xml";
      private static final String JSON = "json";
      private static final String JSON_VARIANT = "+json";
      private static final String XML_DTD = "xml-dtd";
      private static final String ECMASCRIPT = "ecmascript";
  
      /**
       * @param contentType
       *        the contentType of the received message
       * @return the character set to use, or null if not to treat the message as
       *         text
       * @throws InvalidContentTypeException
       *         if the content-type is invalid in some way.
       */
      public static Charset parseContentTypeForTextualCharset(final String contentType) throws InvalidContentTypeException {
          if (contentType == null || contentType.trim().isEmpty()) {
              throw new InvalidContentTypeException("Content type can't be null or empty");
          }
  
          int subTypeSeparator = contentType.indexOf("/");
          if (subTypeSeparator == -1) {
              throw new InvalidContentTypeException("Content type has no '/' separator: " + contentType);
          }
  
          final String type = contentType.substring(0, subTypeSeparator).toLowerCase().trim();
  
          String subTypePart = contentType.substring(subTypeSeparator + 1).toLowerCase().trim();
  
          String parameterPart = null;
          int parameterSeparator = subTypePart.indexOf(";");
          if (parameterSeparator != -1) {
              if (parameterSeparator < subTypePart.length() - 1) {
                  parameterPart = contentType.substring(subTypeSeparator + 1).toLowerCase().trim();
              }
              subTypePart = subTypePart.substring(0, parameterSeparator).trim();
          }
  
          if (subTypePart.isEmpty()) {
              throw new InvalidContentTypeException("Content type has no subtype after '/'" + contentType);
          }
  
          final String subType = subTypePart;
  
          if (isTextual(type, subType)) {
              String charset = findCharset(parameterPart);
              if (charset == null) {
                  charset = UTF_8;
              }
  
              if (UTF_8.equals(charset)) {
                  return StandardCharsets.UTF_8;
              } else {
                  try {
                      return Charset.forName(charset);
                  } catch (IllegalCharsetNameException icne) {
                      throw new InvalidContentTypeException("Illegal charset: " + charset);
                  } catch (UnsupportedCharsetException uce) {
                      throw new InvalidContentTypeException("Unsupported charset: " + charset);
                  }
              }
          }
  
          return null;
      }
  
      //----- Internal Content Type utilities ----------------------------------//
  
      private static boolean isTextual(String type, String subType) {
          if (TEXT.equals(type)) {
              return true;
          }
  
          if (APPLICATION.equals(type)) {
              if (XML.equals(subType) || JSON.equals(subType) || JAVASCRIPT.equals(subType) || subType.endsWith(XML_VARIANT) || subType.endsWith(JSON_VARIANT)
                  || XML_DTD.equals(subType) || ECMASCRIPT.equals(subType)) {
                  return true;
              }
          }
  
          return false;
      }
  
      private static String findCharset(String paramaterPart) {
          String charset = null;
  
          if (paramaterPart != null) {
              StringTokenizer tokenizer = new StringTokenizer(paramaterPart, ";");
              while (tokenizer.hasMoreTokens()) {
                  String parameter = tokenizer.nextToken().trim();
                  int eqIndex = parameter.indexOf('=');
                  if (eqIndex != -1) {
                      String name = parameter.substring(0, eqIndex);
                      if (CHARSET.equalsIgnoreCase(name.trim())) {
                          String value = unquote(parameter.substring(eqIndex + 1));
  
                          charset = value.toUpperCase();
                          break;
                      }
                  }
              }
          }
  
          return charset;
      }
  
      private static String unquote(String s) {
          if (s.length() > 1 && (s.startsWith("\"") && s.endsWith("\""))) {
              return s.substring(1, s.length() - 1);
          } else {
              return s;
          }
      }
  }
  