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/*
 * 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.
 */
package org.apache.qpid.protonj2.test.driver;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.ByteBuffer;

import org.apache.qpid.protonj2.test.driver.codec.Codec;
import org.apache.qpid.protonj2.test.driver.codec.primitives.DescribedType;

/**
 * Encodes AMQP performatives into frames for transmission
 */
public class FrameEncoder {

    public static final byte AMQP_FRAME_TYPE = (byte) 0;
    public static final byte SASL_FRAME_TYPE = (byte) 1;

    private static final int AMQP_PERFORMATIVE_PAD = 512;

    private static final int FRAME_START_BYTE = 0;
    private static final int FRAME_DOFF_BYTE = 4;
    private static final int FRAME_DOFF_SIZE = 2;
    private static final int FRAME_TYPE_BYTE = 5;
    private static final int FRAME_CHANNEL_BYTE = 6;
    private static final int FRAME_HEADER_SIZE = 8;

    private static final byte[] FRAME_HEADER_RESERVED = new byte[FRAME_HEADER_SIZE];

    private final AMQPTestDriver driver;

    private final Codec codec = Codec.Factory.create();

    public FrameEncoder(AMQPTestDriver driver) {
        this.driver = driver;
    }

    public ByteBuffer handleWrite(DescribedType performative, int channel, ByteBuffer payload, Runnable payloadToLarge) {
        return writeFrame(performative, payload, AMQP_FRAME_TYPE, channel, driver.getOutboundMaxFrameSize(), payloadToLarge);
    }

    public ByteBuffer handleWrite(DescribedType performative, int channel) {
        return writeFrame(performative, null, SASL_FRAME_TYPE, (short) 0, driver.getOutboundMaxFrameSize(), null);
    }

    private ByteBuffer writeFrame(DescribedType performative, ByteBuffer payload, byte frameType, int channel, int maxFrameSize, Runnable onPayloadTooLarge) {
        final int outputBufferSize = AMQP_PERFORMATIVE_PAD + (payload != null ? payload.remaining() : 0);

        try (ByteArrayOutputStream baos = new ByteArrayOutputStream(outputBufferSize)) {

            final int performativeSize = writePerformative(performative, payload, maxFrameSize, baos, onPayloadTooLarge);
            final int capacity = maxFrameSize > 0 ? maxFrameSize - performativeSize : Integer.MAX_VALUE;
            final int payloadSize = Math.min(payload == null ? 0 : payload.remaining(), capacity);

            if (payloadSize > 0) {
                byte[] payloadArray = new byte[payloadSize];
                payload.get(payloadArray);
                baos.write(payloadArray);
            }

            final ByteBuffer output = ByteBuffer.wrap(baos.toByteArray());

            endFrame(output, frameType, channel);

            return output.asReadOnlyBuffer();
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    private int writePerformative(DescribedType performative, ByteBuffer payload, int maxFrameSize, ByteArrayOutputStream output, Runnable onPayloadTooLarge) {
        try {
            output.write(FRAME_HEADER_RESERVED); // Reserve space for later Frame preamble

            long encodedSize = 0;

            if (performative != null) {
                try {
                    codec.putDescribedType(performative);
                    encodedSize = codec.encode(output);
                } finally {
                    codec.clear();
                }
            }

            int performativeSize = output.size() - FRAME_HEADER_SIZE;

            if (performativeSize != encodedSize) {
                throw new IllegalStateException(String.format(
                    "Unable to encode performative %s of %d bytes into provided proton buffer, only wrote %d bytes",
                    performative, performativeSize, encodedSize));
            }

            if (onPayloadTooLarge != null && maxFrameSize > 0 && payload != null && (payload.remaining() + performativeSize) > maxFrameSize) {
                // Next iteration will re-encode the frame body again with updates from the 
                // handler and then we can move onto the body portion.
                onPayloadTooLarge.run();
                output.reset();
                performativeSize = writePerformative(performative, payload, maxFrameSize, output, null);
            }

            return performativeSize;
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    private static void endFrame(ByteBuffer output, byte frameType, int channel) {
        output.putInt(FRAME_START_BYTE, output.remaining());
        output.put(FRAME_DOFF_BYTE, (byte) FRAME_DOFF_SIZE);
        output.put(FRAME_TYPE_BYTE, frameType);
        output.putShort(FRAME_CHANNEL_BYTE, (short) channel);
    }
}