//
//  ========================================================================
//  Copyright (c) 1995-2019 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 org.eclipse.jetty.http.MetaData;
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.PushPromiseFrame;
import org.eclipse.jetty.http2.hpack.HpackEncoder;
import org.eclipse.jetty.io.ByteBufferPool;
import org.eclipse.jetty.util.BufferUtil;

public class PushPromiseGenerator extends FrameGenerator
{
    private final HpackEncoder encoder;

    public PushPromiseGenerator(HeaderGenerator headerGenerator, HpackEncoder encoder)
    {
        super(headerGenerator);
        this.encoder = encoder;
    }

    @Override
    public int generate(ByteBufferPool.Lease lease, Frame frame)
    {
        PushPromiseFrame pushPromiseFrame = (PushPromiseFrame)frame;
        return generatePushPromise(lease, pushPromiseFrame.getStreamId(), pushPromiseFrame.getPromisedStreamId(), pushPromiseFrame.getMetaData());
    }

    public int generatePushPromise(ByteBufferPool.Lease lease, int streamId, int promisedStreamId, MetaData metaData)
    {
        if (streamId < 0)
            throw new IllegalArgumentException("Invalid stream id: " + streamId);
        if (promisedStreamId < 0)
            throw new IllegalArgumentException("Invalid promised stream id: " + promisedStreamId);

        int maxFrameSize = getMaxFrameSize();
        // The promised streamId space.
        int extraSpace = 4;
        maxFrameSize -= extraSpace;

        ByteBuffer hpacked = lease.acquire(maxFrameSize, false);
        BufferUtil.clearToFill(hpacked);
        encoder.encode(hpacked, metaData);
        int hpackedLength = hpacked.position();
        BufferUtil.flipToFlush(hpacked, 0);

        int length = hpackedLength + extraSpace;
        int flags = Flags.END_HEADERS;

        ByteBuffer header = generateHeader(lease, FrameType.PUSH_PROMISE, length, flags, streamId);
        header.putInt(promisedStreamId);
        BufferUtil.flipToFlush(header, 0);

        lease.append(header, true);
        lease.append(hpacked, true);

        return Frame.HEADER_LENGTH + length;
    }
}
