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/*
 * Copyright 2013 EMC Corporation. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 * http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 * or in the "license" file accompanying this file. This file 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 com.emc.atmos.api.jersey.provider;

import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

/**
 * Base class to disable chunked encoding in requests by always specifying an accurate byte count in getSize().
 * Subclasses should provide a default constructor, which calls super() with an instance of the underlying writer
 * implementation to be wrapped.
 * 
 * XXX: this is inefficient and should be replaced by a different mechanism.  However, it is the simplest solution to
 * the apache client's insistence on using chunked encoding for all requests with a size of -1 and Jersey's insistence
 * on returning -1 from all message body providers (as well as not allowing users to override the content-length
 * header).
 */
public class MeasuredMessageBodyWriter implements MessageBodyWriter {
    protected MessageBodyWriter wrapped;
    private IOException delayedIOException;
    private WebApplicationException delayedWebAppException;

    public MeasuredMessageBodyWriter( MessageBodyWriter wrapped ) {
        this.wrapped = wrapped;
    }

    @Override
    public boolean isWriteable( Class type, Type genericType, Annotation[] annotations, MediaType mediaType ) {
        return wrapped.isWriteable( type, genericType, annotations, mediaType );
    }

    @Override
    public void writeTo( T t,
                         Class type,
                         Type genericType,
                         Annotation[] annotations,
                         MediaType mediaType,
                         MultivaluedMap httpHeaders,
                         OutputStream entityStream ) throws IOException, WebApplicationException {
        if ( delayedIOException != null ) throw delayedIOException;
        if ( delayedWebAppException != null ) throw delayedWebAppException;
        entityStream.write( getBuffer( t, type, genericType, annotations, mediaType, httpHeaders ) );
    }

    @Override
    public long getSize( T t, Class type, Type genericType, Annotation[] annotations, MediaType mediaType ) {
        try {
            return getBuffer( t, type, genericType, annotations, mediaType, null ).length;
        } catch ( IOException e ) {
            delayedIOException = e;
        } catch ( WebApplicationException e ) {
            delayedWebAppException = e;
        }
        return -1;
    }

    protected synchronized byte[] getBuffer( T t,
                                             Class type,
                                             Type genericType,
                                             Annotation[] annotations,
                                             MediaType mediaType,
                                             MultivaluedMap httpHeaders )
            throws IOException, WebApplicationException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        wrapped.writeTo( t, type, genericType, annotations, mediaType, httpHeaders, baos );
        return baos.toByteArray();
    }
}