/*
 *  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.tomcat.util.net;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.LinkedBlockingDeque;

import org.apache.tomcat.util.buf.ByteBufferHolder;

Provides an expandable set of buffers for writes. Non-blocking writes can be
of any size and may not be able to be written immediately or wholly contained
in the buffer used to perform the writes to the next layer. This class
provides a buffering capability to allow such writes to return immediately
and also allows for the user provided buffers to be re-used / recycled as
required.
/**
 * Provides an expandable set of buffers for writes. Non-blocking writes can be
 * of any size and may not be able to be written immediately or wholly contained
 * in the buffer used to perform the writes to the next layer. This class
 * provides a buffering capability to allow such writes to return immediately
 * and also allows for the user provided buffers to be re-used / recycled as
 * required.
 */
public class WriteBuffer {

    private final int bufferSize;

    private final LinkedBlockingDeque<ByteBufferHolder> buffers = new LinkedBlockingDeque<>();

    public WriteBuffer(int bufferSize) {
        this.bufferSize = bufferSize;
    }

    void clear() {
        buffers.clear();
    }

    void add(byte[] buf, int offset, int length) {
        ByteBufferHolder holder = getByteBufferHolder(length);
        holder.getBuf().put(buf, offset, length);
    }


    public void add(ByteBuffer from) {
        ByteBufferHolder holder = getByteBufferHolder(from.remaining());
        holder.getBuf().put(from);
    }


    private ByteBufferHolder getByteBufferHolder(int capacity) {
        ByteBufferHolder holder = buffers.peekLast();
        if (holder == null || holder.isFlipped() || holder.getBuf().remaining() < capacity) {
            ByteBuffer buffer = ByteBuffer.allocate(Math.max(bufferSize, capacity));
            holder = new ByteBufferHolder(buffer, false);
            buffers.add(holder);
        }
        return holder;
    }


    public boolean isEmpty() {
        return buffers.isEmpty();
    }


    
Create an array of ByteBuffers from the current WriteBuffer, prefixing
that array with the provided ByteBuffers.
Params:
prefixes – The additional ByteBuffers to add to the start of the
                array
Returns:
an array of ByteBuffers from the current WriteBuffer prefixed by
        the provided ByteBuffers/**
     * Create an array of ByteBuffers from the current WriteBuffer, prefixing
     * that array with the provided ByteBuffers.
     *
     * @param prefixes The additional ByteBuffers to add to the start of the
     *                 array
     *
     * @return an array of ByteBuffers from the current WriteBuffer prefixed by
     *         the provided ByteBuffers
     */
    ByteBuffer[] toArray(ByteBuffer... prefixes) {
        List<ByteBuffer> result = new ArrayList<>();
        for (ByteBuffer prefix : prefixes) {
            if (prefix.hasRemaining()) {
                result.add(prefix);
            }
        }
        for (ByteBufferHolder buffer : buffers) {
            buffer.flip();
            result.add(buffer.getBuf());
        }
        buffers.clear();
        return result.toArray(new ByteBuffer[result.size()]);
    }


    boolean write(SocketWrapperBase<?> socketWrapper, boolean blocking) throws IOException {
        Iterator<ByteBufferHolder> bufIter = buffers.iterator();
        boolean dataLeft = false;
        while (!dataLeft && bufIter.hasNext()) {
            ByteBufferHolder buffer = bufIter.next();
            buffer.flip();
            if (blocking) {
                socketWrapper.writeBlocking(buffer.getBuf());
            } else {
                socketWrapper.writeNonBlockingInternal(buffer.getBuf());
            }
            if (buffer.getBuf().remaining() == 0) {
                bufIter.remove();
            } else {
                dataLeft = true;
            }
        }
        return dataLeft;
    }


    public boolean write(Sink sink, boolean blocking) throws IOException {
        Iterator<ByteBufferHolder> bufIter = buffers.iterator();
        boolean dataLeft = false;
        while (!dataLeft && bufIter.hasNext()) {
            ByteBufferHolder buffer = bufIter.next();
            buffer.flip();
            dataLeft = sink.writeFromBuffer(buffer.getBuf(), blocking);
            if (!dataLeft) {
                bufIter.remove();
            }
        }
        return dataLeft;
    }


    
Interface implemented by clients of the WriteBuffer to enable data to be
written back out from the buffer.
/**
     * Interface implemented by clients of the WriteBuffer to enable data to be
     * written back out from the buffer.
     */
    public interface Sink {
        boolean writeFromBuffer(ByteBuffer buffer, boolean block) throws IOException;
    }
}