//
//  ========================================================================
//  Copyright (c) 1995-2018 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.spdy.generator;

import java.nio.ByteBuffer;

import org.eclipse.jetty.io.ByteBufferPool;
import org.eclipse.jetty.spdy.SessionException;
import org.eclipse.jetty.spdy.api.SPDY;
import org.eclipse.jetty.spdy.api.SessionStatus;
import org.eclipse.jetty.spdy.frames.ControlFrame;
import org.eclipse.jetty.spdy.frames.SynReplyFrame;
import org.eclipse.jetty.util.BufferUtil;

public class SynReplyGenerator extends ControlFrameGenerator
{
    private final HeadersBlockGenerator headersBlockGenerator;

    public SynReplyGenerator(ByteBufferPool bufferPool, HeadersBlockGenerator headersBlockGenerator)
    {
        super(bufferPool);
        this.headersBlockGenerator = headersBlockGenerator;
    }

    @Override
    public ByteBuffer generate(ControlFrame frame)
    {
        SynReplyFrame synReply = (SynReplyFrame)frame;
        short version = synReply.getVersion();

        ByteBuffer headersBuffer = headersBlockGenerator.generate(version, synReply.getHeaders());

        int frameBodyLength = getFrameDataLength(version);

        int frameLength = frameBodyLength + headersBuffer.remaining();
        if (frameLength > 0xFF_FF_FF)
        {
            // Too many headers, but unfortunately we have already modified the compression
            // context, so we have no other choice than tear down the connection.
            throw new SessionException(SessionStatus.PROTOCOL_ERROR, "Too many headers");
        }

        int totalLength = ControlFrame.HEADER_LENGTH + frameLength;

        ByteBuffer buffer = getByteBufferPool().acquire(totalLength, Generator.useDirectBuffers);
        BufferUtil.clearToFill(buffer);
        generateControlFrameHeader(synReply, frameLength, buffer);

        buffer.putInt(synReply.getStreamId() & 0x7F_FF_FF_FF);
        writeAdditional(version, buffer);

        buffer.put(headersBuffer);

        buffer.flip();
        return buffer;
    }

    private int getFrameDataLength(short version)
    {
        switch (version)
        {
            case SPDY.V2:
                return 6;
            case SPDY.V3:
                return 4;
            default:
                // Here the version is trusted to be correct; if it's not
                // then it's a bug rather than an application error
                throw new IllegalStateException();
        }
    }

    private void writeAdditional(short version, ByteBuffer buffer)
    {
        switch (version)
        {
            case SPDY.V2:
                buffer.putShort((short)0);
                break;
            case SPDY.V3:
                break;
            default:
                // Here the version is trusted to be correct; if it's not
                // then it's a bug rather than an application error
                throw new IllegalStateException();
        }
    }
}
