/*
 * Copyright (C) 2008-2010, Google Inc.
 * Copyright (C) 2008-2009, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.transport;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.IOException;
import java.io.OutputStream;

import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.util.RawParseUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

Write Git style pkt-line formatting to an output stream.

This class is not thread safe and may issue multiple writes to the underlying
stream for each method call made.

This class performs no buffering on its own. This makes it suitable to
interleave writes performed by this class with writes performed directly
against the underlying OutputStream.
/**
 * Write Git style pkt-line formatting to an output stream.
 * <p>
 * This class is not thread safe and may issue multiple writes to the underlying
 * stream for each method call made.
 * <p>
 * This class performs no buffering on its own. This makes it suitable to
 * interleave writes performed by this class with writes performed directly
 * against the underlying OutputStream.
 */
public class PacketLineOut {
	private static final Logger log = LoggerFactory.getLogger(PacketLineOut.class);

	private final OutputStream out;

	private final byte[] lenbuffer;

	private boolean flushOnEnd;

	private boolean usingSideband;

	
Create a new packet line writer.
Params:
outputStream – 
           stream./**
	 * Create a new packet line writer.
	 *
	 * @param outputStream
	 *            stream.
	 */
	public PacketLineOut(OutputStream outputStream) {
		out = outputStream;
		lenbuffer = new byte[5];
		flushOnEnd = true;
	}

	
Set the flush behavior during end(). 
Params:
flushOnEnd –  if true, a flush-pkt written during end() also flushes the underlying stream./**
	 * Set the flush behavior during {@link #end()}.
	 *
	 * @param flushOnEnd
	 *            if true, a flush-pkt written during {@link #end()} also
	 *            flushes the underlying stream.
	 */
	public void setFlushOnEnd(boolean flushOnEnd) {
		this.flushOnEnd = flushOnEnd;
	}

	
See Also:
setUsingSideband
Returns:
whether to add a sideband designator to each non-flush and
    non-delim packet
Since:
5.5/**
	 * @return whether to add a sideband designator to each non-flush and
	 *     non-delim packet
	 * @see #setUsingSideband
	 * @since 5.5
	 */
	public boolean isUsingSideband() {
		return usingSideband;
	}

	
Params:
value – If true, when writing packet lines, add, as the first
    byte, a sideband designator to each non-flush and non-delim
    packet. See pack-protocol.txt and protocol-v2.txt from the Git
    project for more information, specifically the "side-band" and
    "sideband-all" sections.
Since:
5.5/**
	 * @param value If true, when writing packet lines, add, as the first
	 *     byte, a sideband designator to each non-flush and non-delim
	 *     packet. See pack-protocol.txt and protocol-v2.txt from the Git
	 *     project for more information, specifically the "side-band" and
	 *     "sideband-all" sections.
	 * @since 5.5
	 */
	public void setUsingSideband(boolean value) {
		this.usingSideband = value;
	}

	
Write a UTF-8 encoded string as a single length-delimited packet.
Params:
s – 
           string to write.
Throws:
IOException – 
            the packet could not be written, the stream is corrupted as
            the packet may have been only partially written./**
	 * Write a UTF-8 encoded string as a single length-delimited packet.
	 *
	 * @param s
	 *            string to write.
	 * @throws java.io.IOException
	 *             the packet could not be written, the stream is corrupted as
	 *             the packet may have been only partially written.
	 */
	public void writeString(String s) throws IOException {
		writePacket(Constants.encode(s));
	}

	
Write a binary packet to the stream.
Params:
packet – 
           the packet to write; the length of the packet is equal to the
           size of the byte array.
Throws:
IOException – 
            the packet could not be written, the stream is corrupted as
            the packet may have been only partially written./**
	 * Write a binary packet to the stream.
	 *
	 * @param packet
	 *            the packet to write; the length of the packet is equal to the
	 *            size of the byte array.
	 * @throws java.io.IOException
	 *             the packet could not be written, the stream is corrupted as
	 *             the packet may have been only partially written.
	 */
	public void writePacket(byte[] packet) throws IOException {
		writePacket(packet, 0, packet.length);
	}

	
Write a binary packet to the stream.
Params:
buf – 
           the packet to write
pos –  first index within buf.
len – 
           number of bytes to write.
Throws:
IOException – 
            the packet could not be written, the stream is corrupted as
            the packet may have been only partially written.
Since:
4.5/**
	 * Write a binary packet to the stream.
	 *
	 * @param buf
	 *            the packet to write
	 * @param pos
	 *            first index within {@code buf}.
	 * @param len
	 *            number of bytes to write.
	 * @throws java.io.IOException
	 *             the packet could not be written, the stream is corrupted as
	 *             the packet may have been only partially written.
	 * @since 4.5
	 */
	public void writePacket(byte[] buf, int pos, int len) throws IOException {
		if (usingSideband) {
			formatLength(len + 5);
			out.write(lenbuffer, 0, 4);
			out.write(1);
		} else {
			formatLength(len + 4);
			out.write(lenbuffer, 0, 4);
		}
		out.write(buf, pos, len);
		if (log.isDebugEnabled()) {
			String s = RawParseUtils.decode(UTF_8, buf, pos, len);
			log.debug("git> " + s); //$NON-NLS-1$
		}
	}

	
Write a packet delim marker (0001).
Throws:
IOException – 
            the marker could not be written, the stream is corrupted
            as the marker may have been only partially written.
Since:
5.0/**
	 * Write a packet delim marker (0001).
	 *
	 * @throws java.io.IOException
	 *             the marker could not be written, the stream is corrupted
	 *             as the marker may have been only partially written.
	 * @since 5.0
	 */
	public void writeDelim() throws IOException {
		formatLength(1);
		out.write(lenbuffer, 0, 4);
		log.debug("git> 0001"); //$NON-NLS-1$
	}

	
Write a packet end marker, sometimes referred to as a flush command.

Technically this is a magical packet type which can be detected
separately from an empty string or an empty packet.

Implicitly performs a flush on the underlying OutputStream to ensure the
peer will receive all data written thus far.
Throws:
IOException – 
            the end marker could not be written, the stream is corrupted
            as the end marker may have been only partially written./**
	 * Write a packet end marker, sometimes referred to as a flush command.
	 * <p>
	 * Technically this is a magical packet type which can be detected
	 * separately from an empty string or an empty packet.
	 * <p>
	 * Implicitly performs a flush on the underlying OutputStream to ensure the
	 * peer will receive all data written thus far.
	 *
	 * @throws java.io.IOException
	 *             the end marker could not be written, the stream is corrupted
	 *             as the end marker may have been only partially written.
	 */
	public void end() throws IOException {
		formatLength(0);
		out.write(lenbuffer, 0, 4);
		log.debug("git> 0000"); //$NON-NLS-1$
		if (flushOnEnd)
			flush();
	}

	
Flush the underlying OutputStream.

Performs a flush on the underlying OutputStream to ensure the peer will
receive all data written thus far.
Throws:
IOException – 
            the underlying stream failed to flush./**
	 * Flush the underlying OutputStream.
	 * <p>
	 * Performs a flush on the underlying OutputStream to ensure the peer will
	 * receive all data written thus far.
	 *
	 * @throws java.io.IOException
	 *             the underlying stream failed to flush.
	 */
	public void flush() throws IOException {
		out.flush();
	}

	private static final byte[] hexchar = { '0', '1', '2', '3', '4', '5', '6',
			'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

	private void formatLength(int w) {
		formatLength(lenbuffer, w);
	}

	static void formatLength(byte[] lenbuffer, int w) {
		int o = 3;
		while (o >= 0 && w != 0) {
			lenbuffer[o--] = hexchar[w & 0xf];
			w >>>= 4;
		}
		while (o >= 0)
			lenbuffer[o--] = '0';
	}
}