/*
 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/protocol/ResponseContent.java $
 * $Revision: 573864 $
 * $Date: 2007-09-08 08:53:25 -0700 (Sat, 08 Sep 2007) $
 *
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.protocol;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpException;
import org.apache.http.HttpResponse;
import org.apache.http.HttpResponseInterceptor;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.ProtocolVersion;
import org.apache.http.ProtocolException;

/**
 * A response interceptor that sets up entity-related headers.
 * For use on the server side.
 *
 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
 *
 * @version $Revision: 573864 $
 * 
 * @since 4.0
 */
public class ResponseContent implements HttpResponseInterceptor {

    public ResponseContent() {
        super();
    }
    
    public void process(final HttpResponse response, final HttpContext context) 
            throws HttpException, IOException {
        if (response == null) {
            throw new IllegalArgumentException("HTTP request may not be null");
        }
        if (response.containsHeader(HTTP.TRANSFER_ENCODING)) {
            throw new ProtocolException("Transfer-encoding header already present");
        }
        if (response.containsHeader(HTTP.CONTENT_LEN)) {
            throw new ProtocolException("Content-Length header already present");
        }
        ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            long len = entity.getContentLength();
            if (entity.isChunked() && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
                response.addHeader(HTTP.TRANSFER_ENCODING, HTTP.CHUNK_CODING);
            } else if (len >= 0) {
                response.addHeader(HTTP.CONTENT_LEN, Long.toString(entity.getContentLength()));
            }
            // Specify a content type if known
            if (entity.getContentType() != null && !response.containsHeader(
                    HTTP.CONTENT_TYPE )) {
                response.addHeader(entity.getContentType()); 
            }
            // Specify a content encoding if known
            if (entity.getContentEncoding() != null && !response.containsHeader(
                    HTTP.CONTENT_ENCODING)) {
                response.addHeader(entity.getContentEncoding()); 
            }
        } else {
            int status = response.getStatusLine().getStatusCode();
            if (status != HttpStatus.SC_NO_CONTENT 
                    && status != HttpStatus.SC_NOT_MODIFIED
                    && status != HttpStatus.SC_RESET_CONTENT) {
                response.addHeader(HTTP.CONTENT_LEN, "0");
            }
        }
    }
    
}