/*
    * 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 org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.util.internal.StringUtil;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * The default {@link HttpChunkTrailer} implementation.
   */
  public class DefaultHttpChunkTrailer implements HttpChunkTrailer {
  
      private final HttpHeaders trailingHeaders = new TrailingHeaders(true);
  
      public boolean isLast() {
          return true;
      }
  
      public ChannelBuffer getContent() {
          return ChannelBuffers.EMPTY_BUFFER;
      }
  
      public void setContent(ChannelBuffer content) {
          throw new IllegalStateException("read-only");
      }
  
      public HttpHeaders trailingHeaders() {
          return trailingHeaders;
      }
  
      @Override
      public String toString() {
          StringBuilder buf = new StringBuilder(super.toString());
          buf.append(StringUtil.NEWLINE);
          appendHeaders(buf);
  
          // Remove the last newline.
          buf.setLength(buf.length() - StringUtil.NEWLINE.length());
          return buf.toString();
      }
  
      private void appendHeaders(StringBuilder buf) {
          for (Map.Entry<String, String> e: trailingHeaders()) {
              buf.append(e.getKey());
              buf.append(": ");
              buf.append(e.getValue());
              buf.append(StringUtil.NEWLINE);
          }
      }
  
      private static final class TrailingHeaders extends DefaultHttpHeaders {
  
          TrailingHeaders(boolean validateHeaders) {
              super(validateHeaders);
          }
  
          @Override
          public HttpHeaders add(String name, Object value) {
              if (validate) {
                  validateName(name);
              }
              return super.add(name, value);
          }
  
          @Override
          public HttpHeaders add(String name, Iterable<?> values) {
              if (validate) {
                  validateName(name);
              }
              return super.add(name, values);
          }
  
          @Override
          public HttpHeaders set(String name, Iterable<?> values) {
              if (validate) {
                  validateName(name);
              }
              return super.set(name, values);
          }
  
          @Override
         public HttpHeaders set(String name, Object value) {
             if (validate) {
                 validateName(name);
             }
             return super.set(name, value);
         }
 
         private static void validateName(String name) {
             if (name.equalsIgnoreCase(HttpHeaders.Names.CONTENT_LENGTH) ||
                     name.equalsIgnoreCase(HttpHeaders.Names.TRANSFER_ENCODING) ||
                     name.equalsIgnoreCase(HttpHeaders.Names.TRAILER)) {
                 throw new IllegalArgumentException(
                         "prohibited trailing header: " + name);
             }
         }
     }
 }