//
//  ========================================================================
//  Copyright (c) 1995-2017 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.http2.generator;

import java.nio.ByteBuffer;
import java.util.Arrays;

import org.eclipse.jetty.http2.Flags;
import org.eclipse.jetty.http2.frames.Frame;
import org.eclipse.jetty.http2.frames.FrameType;
import org.eclipse.jetty.http2.frames.GoAwayFrame;
import org.eclipse.jetty.io.ByteBufferPool;
import org.eclipse.jetty.util.BufferUtil;

public class GoAwayGenerator extends FrameGenerator
{
    public GoAwayGenerator(HeaderGenerator headerGenerator)
    {
        super(headerGenerator);
    }

    @Override
    public int generate(ByteBufferPool.Lease lease, Frame frame)
    {
        GoAwayFrame goAwayFrame = (GoAwayFrame)frame;
        return generateGoAway(lease, goAwayFrame.getLastStreamId(), goAwayFrame.getError(), goAwayFrame.getPayload());
    }

    public int generateGoAway(ByteBufferPool.Lease lease, int lastStreamId, int error, byte[] payload)
    {
        if (lastStreamId < 0)
            throw new IllegalArgumentException("Invalid last stream id: " + lastStreamId);

        // The last streamId + the error code.
        int fixedLength = 4 + 4;

        // Make sure we don't exceed the default frame max length.
        int maxPayloadLength = Frame.DEFAULT_MAX_LENGTH - fixedLength;
        if (payload != null && payload.length > maxPayloadLength)
            payload = Arrays.copyOfRange(payload, 0, maxPayloadLength);

        int length = fixedLength + (payload != null ? payload.length : 0);
        ByteBuffer header = generateHeader(lease, FrameType.GO_AWAY, length, Flags.NONE, 0);

        header.putInt(lastStreamId);
        header.putInt(error);

        if (payload != null)
            header.put(payload);

        BufferUtil.flipToFlush(header, 0);
        lease.append(header, true);

        return Frame.HEADER_LENGTH + length;
    }
}