/*
    * Copyright (C) 2008, 2010 Google Inc.
    * Copyright (C) 2008, 2009 Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2008, 2020 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.InputStream;
  import java.io.UncheckedIOException;
  import java.text.MessageFormat;
  import java.util.Iterator;
  
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.MutableObjectId;
  import org.eclipse.jgit.util.IO;
  import org.eclipse.jgit.util.RawParseUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Read Git style pkt-line formatting from an input stream.
   * <p>
   * This class is not thread safe and may issue multiple reads to the underlying
   * stream for each method call made.
   * <p>
   * This class performs no buffering on its own. This makes it suitable to
   * interleave reads performed by this class with reads performed directly
   * against the underlying InputStream.
   */
  public class PacketLineIn {
  	private static final Logger log = LoggerFactory.getLogger(PacketLineIn.class);
  
  	/**
  	 * Magic return from {@link #readString()} when a flush packet is found.
  	 *
  	 * @deprecated Callers should use {@link #isEnd(String)} to check if a
  	 *             string is the end marker, or
  	 *             {@link PacketLineIn#readStrings()} to iterate over all
  	 *             strings in the input stream until the marker is reached.
  	 */
  	@Deprecated
  	public static final String END = new String(); /* must not string pool */
  
  	/**
  	 * Magic return from {@link #readString()} when a delim packet is found.
  	 *
  	 * @since 5.0
  	 * @deprecated Callers should use {@link #isDelimiter(String)} to check if a
  	 *             string is the delimiter.
  	 */
  	@Deprecated
  	public static final String DELIM = new String(); /* must not string pool */
  
  	enum AckNackResult {
  		/** NAK */
  		NAK,
  		/** ACK */
  		ACK,
  		/** ACK + continue */
  		ACK_CONTINUE,
  		/** ACK + common */
  		ACK_COMMON,
  		/** ACK + ready */
  		ACK_READY;
  	}
  
  	private final byte[] lineBuffer = new byte[SideBandOutputStream.SMALL_BUF];
  	private final InputStream in;
  	private long limit;
  
  	/**
  	 * Create a new packet line reader.
  	 *
  	 * @param in
  	 *            the input stream to consume.
  	 */
  	public PacketLineIn(InputStream in) {
  		this(in, 0);
  	}
  
  	/**
  	 * Create a new packet line reader.
  	 *
  	 * @param in
  	 *            the input stream to consume.
  	 * @param limit
  	 *            bytes to read from the input; unlimited if set to 0.
  	 * @since 4.7
 	 */
 	public PacketLineIn(InputStream in, long limit) {
 		this.in = in;
 		this.limit = limit;
 	}
 
 	AckNackResult readACK(MutableObjectId returnedId) throws IOException {
 		final String line = readString();
 		if (line.length() == 0)
 			throw new PackProtocolException(JGitText.get().expectedACKNAKFoundEOF);
 		if ("NAK".equals(line)) //$NON-NLS-1$
 			return AckNackResult.NAK;
 		if (line.startsWith("ACK ")) { //$NON-NLS-1$
 			returnedId.fromString(line.substring(4, 44));
 			if (line.length() == 44)
 				return AckNackResult.ACK;
 
 			final String arg = line.substring(44);
 			switch (arg) {
 			case " continue": //$NON-NLS-1$
 				return AckNackResult.ACK_CONTINUE;
 			case " common": //$NON-NLS-1$
 				return AckNackResult.ACK_COMMON;
 			case " ready": //$NON-NLS-1$
 				return AckNackResult.ACK_READY;
 			default:
 				break;
 			}
 		}
 		if (line.startsWith("ERR ")) //$NON-NLS-1$
 			throw new PackProtocolException(line.substring(4));
 		throw new PackProtocolException(MessageFormat.format(JGitText.get().expectedACKNAKGot, line));
 	}
 
 	/**
 	 * Read a single UTF-8 encoded string packet from the input stream.
 	 * <p>
 	 * If the string ends with an LF, it will be removed before returning the
 	 * value to the caller. If this automatic trimming behavior is not desired,
 	 * use {@link #readStringRaw()} instead.
 	 *
 	 * @return the string. {@link #END} if the string was the magic flush
 	 *         packet, {@link #DELIM} if the string was the magic DELIM
 	 *         packet.
 	 * @throws java.io.IOException
 	 *             the stream cannot be read.
 	 */
 	public String readString() throws IOException {
 		int len = readLength();
 		if (len == 0) {
 			log.debug("git< 0000"); //$NON-NLS-1$
 			return END;
 		}
 		if (len == 1) {
 			log.debug("git< 0001"); //$NON-NLS-1$
 			return DELIM;
 		}
 
 		len -= 4; // length header (4 bytes)
 		if (len == 0) {
 			log.debug("git< "); //$NON-NLS-1$
 			return ""; //$NON-NLS-1$
 		}
 
 		byte[] raw;
 		if (len <= lineBuffer.length)
 			raw = lineBuffer;
 		else
 			raw = new byte[len];
 
 		IO.readFully(in, raw, 0, len);
 		if (raw[len - 1] == '\n')
 			len--;
 
 		String s = RawParseUtils.decode(UTF_8, raw, 0, len);
 		log.debug("git< " + s); //$NON-NLS-1$
 		return s;
 	}
 
 	/**
 	 * Get an iterator to read strings from the input stream.
 	 *
 	 * @return an iterator that calls {@link #readString()} until {@link #END}
 	 *         is encountered.
 	 *
 	 * @throws IOException
 	 *             on failure to read the initial packet line.
 	 * @since 5.4
 	 */
 	public PacketLineInIterator readStrings() throws IOException {
 		return new PacketLineInIterator(this);
 	}
 
 	/**
 	 * Read a single UTF-8 encoded string packet from the input stream.
 	 * <p>
 	 * Unlike {@link #readString()} a trailing LF will be retained.
 	 *
 	 * @return the string. {@link #END} if the string was the magic flush
 	 *         packet.
 	 * @throws java.io.IOException
 	 *             the stream cannot be read.
 	 */
 	public String readStringRaw() throws IOException {
 		int len = readLength();
 		if (len == 0) {
 			log.debug("git< 0000"); //$NON-NLS-1$
 			return END;
 		}
 
 		len -= 4; // length header (4 bytes)
 
 		byte[] raw;
 		if (len <= lineBuffer.length)
 			raw = lineBuffer;
 		else
 			raw = new byte[len];
 
 		IO.readFully(in, raw, 0, len);
 
 		String s = RawParseUtils.decode(UTF_8, raw, 0, len);
 		log.debug("git< " + s); //$NON-NLS-1$
 		return s;
 	}
 
 	/**
 	 * Check if a string is the delimiter marker.
 	 *
 	 * @param s
 	 *            the string to check
 	 * @return true if the given string is {@link #DELIM}, otherwise false.
 	 * @since 5.4
 	 */
 	@SuppressWarnings({ "ReferenceEquality", "StringEquality" })
 	public static boolean isDelimiter(String s) {
 		return s == DELIM;
 	}
 
 	/**
 	 * Get the delimiter marker.
 	 * <p>
 	 * Intended for use only in tests.
 	 *
 	 * @return The delimiter marker.
 	 */
 	static String delimiter() {
 		return DELIM;
 	}
 
 	/**
 	 * Get the end marker.
 	 * <p>
 	 * Intended for use only in tests.
 	 *
 	 * @return The end marker.
 	 */
 	static String end() {
 		return END;
 	}
 
 	/**
 	 * Check if a string is the packet end marker.
 	 *
 	 * @param s
 	 *            the string to check
 	 * @return true if the given string is {@link #END}, otherwise false.
 	 * @since 5.4
 	 */
 	@SuppressWarnings({ "ReferenceEquality", "StringEquality" })
 	public static boolean isEnd(String s) {
 		return s == END;
 	}
 
 	void discardUntilEnd() throws IOException {
 		for (;;) {
 			int n = readLength();
 			if (n == 0) {
 				break;
 			}
 			IO.skipFully(in, n - 4);
 		}
 	}
 
 	int readLength() throws IOException {
 		IO.readFully(in, lineBuffer, 0, 4);
 		int len;
 		try {
 			len = RawParseUtils.parseHexInt16(lineBuffer, 0);
 		} catch (ArrayIndexOutOfBoundsException err) {
 			throw invalidHeader(err);
 		}
 
 		if (len == 0) {
 			return 0;
 		} else if (len == 1) {
 			return 1;
 		} else if (len < 4) {
 			throw invalidHeader();
 		}
 
 		if (limit != 0) {
 			int n = len - 4;
 			if (limit < n) {
 				limit = -1;
 				try {
 					IO.skipFully(in, n);
 				} catch (IOException e) {
 					// Ignore failure discarding packet over limit.
 				}
 				throw new InputOverLimitIOException();
 			}
 			// if set limit must not be 0 (means unlimited).
 			limit = n < limit ? limit - n : -1;
 		}
 		return len;
 	}
 
 	private IOException invalidHeader() {
 		return new IOException(MessageFormat.format(JGitText.get().invalidPacketLineHeader,
 				"" + (char) lineBuffer[0] + (char) lineBuffer[1] //$NON-NLS-1$
 				+ (char) lineBuffer[2] + (char) lineBuffer[3]));
 	}
 
 	private IOException invalidHeader(Throwable cause) {
 		IOException ioe = invalidHeader();
 		ioe.initCause(cause);
 		return ioe;
 	}
 
 	/**
 	 * IOException thrown by read when the configured input limit is exceeded.
 	 *
 	 * @since 4.7
 	 */
 	public static class InputOverLimitIOException extends IOException {
 		private static final long serialVersionUID = 1L;
 	}
 
 	/**
 	 * Iterator over packet lines.
 	 * <p>
 	 * Calls {@link #readString()} on the {@link PacketLineIn} until
 	 * {@link #END} is encountered.
 	 *
 	 * @since 5.4
 	 *
 	 */
 	public static class PacketLineInIterator implements Iterable<String> {
 		private PacketLineIn in;
 
 		private String current;
 
 		PacketLineInIterator(PacketLineIn in) throws IOException {
 			this.in = in;
 			current = in.readString();
 		}
 
 		@Override
 		public Iterator<String> iterator() {
 			return new Iterator<String>() {
 				@Override
 				public boolean hasNext() {
 					return !PacketLineIn.isEnd(current);
 				}
 
 				@Override
 				public String next() {
 					String next = current;
 					try {
 						current = in.readString();
 					} catch (IOException e) {
 						throw new UncheckedIOException(e);
 					}
 					return next;
 				}
 			};
 		}
 
 	}
 }