/*
 * 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.cassandra.io.util;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.WritableByteChannel;

import io.netty.util.concurrent.FastThreadLocal;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.utils.ByteBufferUtil;

Abstract base class for DataOutputStreams that accept writes from ByteBuffer or Memory and also provide
access to the underlying WritableByteChannel associated with their output stream.
If no channel is provided by derived classes then a wrapper channel is provided.
/**
 * Abstract base class for DataOutputStreams that accept writes from ByteBuffer or Memory and also provide
 * access to the underlying WritableByteChannel associated with their output stream.
 *
 * If no channel is provided by derived classes then a wrapper channel is provided.
 */
public abstract class DataOutputStreamPlus extends OutputStream implements DataOutputPlus
{
    //Dummy wrapper channel for derived implementations that don't have a channel
    protected final WritableByteChannel channel;

    protected DataOutputStreamPlus()
    {
        this.channel = newDefaultChannel();
    }

    protected DataOutputStreamPlus(WritableByteChannel channel)
    {
        this.channel = channel;
    }

    private static int MAX_BUFFER_SIZE =
            Integer.getInteger(Config.PROPERTY_PREFIX + "data_output_stream_plus_temp_buffer_size", 8192);

    /*
     * Factored out into separate method to create more flexibility around inlining
     */
    protected static byte[] retrieveTemporaryBuffer(int minSize)
    {
        byte[] bytes = tempBuffer.get();
        if (bytes.length < Math.min(minSize, MAX_BUFFER_SIZE))
        {
            // increase in powers of 2, to avoid wasted repeat allocations
            bytes = new byte[Math.min(MAX_BUFFER_SIZE, 2 * Integer.highestOneBit(minSize))];
            tempBuffer.set(bytes);
        }
        return bytes;
    }

    private static final FastThreadLocal<byte[]> tempBuffer = new FastThreadLocal<byte[]>()
    {
        @Override
        public byte[] initialValue()
        {
            return new byte[16];
        }
    };

    // Derived classes can override and *construct* a real channel, if it is not possible to provide one to the constructor
    protected WritableByteChannel newDefaultChannel()
    {
        return new WritableByteChannel()
        {

            @Override
            public boolean isOpen()
            {
                return true;
            }

            @Override
            public void close()
            {
            }

            @Override
            public int write(ByteBuffer src) throws IOException
            {
                int toWrite = src.remaining();

                if (src.hasArray())
                {
                    DataOutputStreamPlus.this.write(src.array(), src.arrayOffset() + src.position(), src.remaining());
                    src.position(src.limit());
                    return toWrite;
                }

                if (toWrite < 16)
                {
                    int offset = src.position();
                    for (int i = 0 ; i < toWrite ; i++)
                        DataOutputStreamPlus.this.write(src.get(i + offset));
                    src.position(src.limit());
                    return toWrite;
                }

                byte[] buf = retrieveTemporaryBuffer(toWrite);

                int totalWritten = 0;
                while (totalWritten < toWrite)
                {
                    int toWriteThisTime = Math.min(buf.length, toWrite - totalWritten);

                    ByteBufferUtil.arrayCopy(src, src.position() + totalWritten, buf, 0, toWriteThisTime);

                    DataOutputStreamPlus.this.write(buf, 0, toWriteThisTime);

                    totalWritten += toWriteThisTime;
                }

                src.position(src.limit());
                return totalWritten;
            }

        };
    }

}