/*
 * ====================================================================
 * 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 ch.boye.httpclientandroidlib.protocol;

import java.io.IOException;

import ch.boye.httpclientandroidlib.HttpEntity;
import ch.boye.httpclientandroidlib.HttpEntityEnclosingRequest;
import ch.boye.httpclientandroidlib.HttpException;
import ch.boye.httpclientandroidlib.HttpRequest;
import ch.boye.httpclientandroidlib.HttpRequestInterceptor;
import ch.boye.httpclientandroidlib.HttpVersion;
import ch.boye.httpclientandroidlib.ProtocolVersion;
import ch.boye.httpclientandroidlib.annotation.Immutable;
import ch.boye.httpclientandroidlib.params.HttpProtocolParams;

/**
 * RequestExpectContinue is responsible for enabling the 'expect-continue'
 * handshake by adding <code>Expect</code> header. This interceptor is
 * recommended for client side protocol processors.
 * <p>
 * The following parameters can be used to customize the behavior of this
 * class:
 * <ul>
 *  <li>{@link ch.boye.httpclientandroidlib.params.CoreProtocolPNames#USE_EXPECT_CONTINUE}</li>
 * </ul>
 *
 * @since 4.0
 */
@Immutable
public class RequestExpectContinue implements HttpRequestInterceptor {

    public RequestExpectContinue() {
        super();
    }

    public void process(final HttpRequest request, final HttpContext context)
            throws HttpException, IOException {
        if (request == null) {
            throw new IllegalArgumentException("HTTP request may not be null");
        }
        if (request instanceof HttpEntityEnclosingRequest) {
            HttpEntity entity = ((HttpEntityEnclosingRequest)request).getEntity();
            // Do not send the expect header if request body is known to be empty
            if (entity != null && entity.getContentLength() != 0) {
                ProtocolVersion ver = request.getRequestLine().getProtocolVersion();
                if (HttpProtocolParams.useExpectContinue(request.getParams())
                        && !ver.lessEquals(HttpVersion.HTTP_1_0)) {
                    request.addHeader(HTTP.EXPECT_DIRECTIVE, HTTP.EXPECT_CONTINUE);
                }
            }
        }
    }

}
