/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.handler.codec.http;
  
  import java.util.List;
  
  final class HttpCodecUtil {
  
      static void validateHeaderName(String name) {
          if (name == null) {
              throw new NullPointerException("name");
          }
          for (int i = 0; i < name.length(); i ++) {
              char c = name.charAt(i);
              if (c > 127) {
                  throw new IllegalArgumentException(
                          "name contains non-ascii character: " + name);
              }
  
              // Check prohibited characters.
              switch (c) {
              case '\t': case '\n': case 0x0b: case '\f': case '\r':
              case ' ':  case ',':  case ':':  case ';':  case '=':
                  throw new IllegalArgumentException(
                          "name contains one of the following prohibited characters: " +
                          "=,;: \\t\\r\\n\\v\\f: " + name);
              }
          }
      }
  
      static void validateHeaderValue(String value) {
          if (value == null) {
              throw new NullPointerException("value");
          }
  
          // 0 - the previous character was neither CR nor LF
          // 1 - the previous character was CR
          // 2 - the previous character was LF
          int state = 0;
  
          for (int i = 0; i < value.length(); i ++) {
              char c = value.charAt(i);
  
              // Check the absolutely prohibited characters.
              switch (c) {
              case 0x0b: // Vertical tab
                  throw new IllegalArgumentException(
                          "value contains a prohibited character '\\v': " + value);
              case '\f':
                  throw new IllegalArgumentException(
                          "value contains a prohibited character '\\f': " + value);
              }
  
              // Check the CRLF (HT | SP) pattern
              switch (state) {
              case 0:
                  switch (c) {
                  case '\r':
                      state = 1;
                      break;
                  case '\n':
                      state = 2;
                      break;
                  }
                  break;
              case 1:
                  switch (c) {
                  case '\n':
                      state = 2;
                      break;
                  default:
                      throw new IllegalArgumentException(
                              "Only '\\n' is allowed after '\\r': " + value);
                  }
                  break;
              case 2:
                  switch (c) {
                  case '\t': case ' ':
                      state = 0;
                      break;
                  default:
                      throw new IllegalArgumentException(
                              "Only ' ' and '\\t' are allowed after '\\n': " + value);
                  }
              }
          }
 
         if (state != 0) {
             throw new IllegalArgumentException(
                     "value must not end with '\\r' or '\\n':" + value);
         }
     }
 
     static boolean isTransferEncodingChunked(HttpMessage m) {
         List<String> chunked = m.getHeaders(HttpHeaders.Names.TRANSFER_ENCODING);
         if (chunked.isEmpty()) {
             return false;
         }
 
         for (String v: chunked) {
             if (v.equalsIgnoreCase(HttpHeaders.Values.CHUNKED)) {
                 return true;
             }
         }
         return false;
     }
 
     static void removeTransferEncodingChunked(HttpMessage m) {
         List<String> values = m.getHeaders(HttpHeaders.Names.TRANSFER_ENCODING);
         values.remove(HttpHeaders.Values.CHUNKED);
         m.setHeader(HttpHeaders.Names.TRANSFER_ENCODING, values);
     }
 
     static boolean isContentLengthSet(HttpMessage m) {
         List<String> contentLength = m.getHeaders(HttpHeaders.Names.CONTENT_LENGTH);
         return !contentLength.isEmpty();
     }
 
     private HttpCodecUtil() {
     }
 }