//
//  ========================================================================
//  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.websocket.common.message;

import java.io.IOException;
import java.io.Writer;
import java.nio.ByteBuffer;

import org.eclipse.jetty.io.ByteBufferPool;
import org.eclipse.jetty.util.BufferUtil;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.websocket.api.BatchMode;
import org.eclipse.jetty.websocket.api.WriteCallback;
import org.eclipse.jetty.websocket.api.extensions.OutgoingFrames;
import org.eclipse.jetty.websocket.common.BlockingWriteCallback;
import org.eclipse.jetty.websocket.common.BlockingWriteCallback.WriteBlocker;
import org.eclipse.jetty.websocket.common.WebSocketSession;
import org.eclipse.jetty.websocket.common.frames.TextFrame;

/**
 * Support for writing a single WebSocket TEXT message via a {@link Writer}
 * <p>
 * Note: Per WebSocket spec, all WebSocket TEXT messages must be encoded in UTF-8
 */
public class MessageWriter extends Writer
{
    private static final Logger LOG = Log.getLogger(MessageWriter.class);

    private final OutgoingFrames outgoing;
    private final ByteBufferPool bufferPool;
    private final BlockingWriteCallback blocker;
    private long frameCount;
    private TextFrame frame;
    private ByteBuffer buffer;
    private Utf8CharBuffer utf;
    private WriteCallback callback;
    private boolean closed;

    public MessageWriter(WebSocketSession session)
    {
        this(session.getOutgoingHandler(), session.getPolicy().getMaxTextMessageBufferSize(), session.getBufferPool());
    }

    public MessageWriter(OutgoingFrames outgoing, int bufferSize, ByteBufferPool bufferPool)
    {
        this.outgoing = outgoing;
        this.bufferPool = bufferPool;
        this.blocker = new BlockingWriteCallback();
        this.buffer = bufferPool.acquire(bufferSize, true);
        BufferUtil.flipToFill(buffer);
        this.frame = new TextFrame();
        this.utf = Utf8CharBuffer.wrap(buffer);
    }

    @Override
    public void write(char[] chars, int off, int len) throws IOException
    {
        try
        {
            send(chars, off, len);
        }
        catch (Throwable x)
        {
            // Notify without holding locks.
            notifyFailure(x);
            throw x;
        }
    }

    @Override
    public void write(int c) throws IOException
    {
        try
        {
            send(new char[]{(char)c}, 0, 1);
        }
        catch (Throwable x)
        {
            // Notify without holding locks.
            notifyFailure(x);
            throw x;
        }
    }

    @Override
    public void flush() throws IOException
    {
        try
        {
            flush(false);
        }
        catch (Throwable x)
        {
            // Notify without holding locks.
            notifyFailure(x);
            throw x;
        }
    }

    @Override
    public void close() throws IOException
    {
        try
        {
            flush(true);
            bufferPool.release(buffer);
            if (LOG.isDebugEnabled())
                LOG.debug("Stream closed, {} frames sent", frameCount);
            // Notify without holding locks.
            notifySuccess();
        }
        catch (Throwable x)
        {
            // Notify without holding locks.
            notifyFailure(x);
            throw x;
        }
    }

    private void flush(boolean fin) throws IOException
    {
        synchronized (this)
        {
            if (closed)
                throw new IOException("Stream is closed");

            closed = fin;

            ByteBuffer data = utf.getByteBuffer();
            if (LOG.isDebugEnabled())
                LOG.debug("flush({}): {}", fin, BufferUtil.toDetailString(buffer));
            frame.setPayload(data);
            frame.setFin(fin);

            try (WriteBlocker b = blocker.acquireWriteBlocker())
            {
                outgoing.outgoingFrame(frame, b, BatchMode.OFF);
                b.block();
            }

            ++frameCount;
            // Any flush after the first will be a CONTINUATION frame.
            frame.setIsContinuation();

            utf.clear();
        }
    }

    private void send(char[] chars, int offset, int length) throws IOException
    {
        synchronized (this)
        {
            if (closed)
                throw new IOException("Stream is closed");

            while (length > 0)
            {
                // There may be no space available, we want
                // to handle correctly when space == 0.
                int space = utf.remaining();
                int size = Math.min(space, length);
                utf.append(chars, offset, size);
                offset += size;
                length -= size;
                if (length > 0)
                {
                    // If we could not write everything, it means
                    // that the buffer was full, so flush it.
                    flush(false);
                }
            }
        }
    }

    public void setCallback(WriteCallback callback)
    {
        synchronized (this)
        {
            this.callback = callback;
        }
    }

    private void notifySuccess()
    {
        WriteCallback callback;
        synchronized (this)
        {
            callback = this.callback;
        }
        if (callback != null)
        {
            callback.writeSuccess();
        }
    }

    private void notifyFailure(Throwable failure)
    {
        WriteCallback callback;
        synchronized (this)
        {
            callback = this.callback;
        }
        if (callback != null)
        {
            callback.writeFailed(failure);
        }
    }
}
