/*
 * Copyright (C) 2008-2009, Google Inc.
 * Copyright (C) 2009, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2006-2008, 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.util;

import java.io.EOFException;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;

import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.util.io.SilentFileInputStream;

Input/Output utilities
/**
 * Input/Output utilities
 */
public class IO {

	
Read an entire local file into memory as a byte array.
Params:
path – 
           location of the file to read.
Throws:
FileNotFoundException – 
            the file does not exist.
IOException – 
            the file exists, but its contents cannot be read.
Returns:
complete contents of the requested local file./**
	 * Read an entire local file into memory as a byte array.
	 *
	 * @param path
	 *            location of the file to read.
	 * @return complete contents of the requested local file.
	 * @throws java.io.FileNotFoundException
	 *             the file does not exist.
	 * @throws java.io.IOException
	 *             the file exists, but its contents cannot be read.
	 */
	public static final byte[] readFully(File path)
			throws FileNotFoundException, IOException {
		return IO.readFully(path, Integer.MAX_VALUE);
	}

	
Read at most limit bytes from the local file into memory as a byte array.
Params:
path – 
           location of the file to read.
limit – 
           maximum number of bytes to read, if the file is larger than
           only the first limit number of bytes are returned
Throws:
FileNotFoundException – 
            the file does not exist.
IOException – 
            the file exists, but its contents cannot be read.
Returns:
complete contents of the requested local file. If the contents
        exceeds the limit, then only the limit is returned./**
	 * Read at most limit bytes from the local file into memory as a byte array.
	 *
	 * @param path
	 *            location of the file to read.
	 * @param limit
	 *            maximum number of bytes to read, if the file is larger than
	 *            only the first limit number of bytes are returned
	 * @return complete contents of the requested local file. If the contents
	 *         exceeds the limit, then only the limit is returned.
	 * @throws java.io.FileNotFoundException
	 *             the file does not exist.
	 * @throws java.io.IOException
	 *             the file exists, but its contents cannot be read.
	 */
	public static final byte[] readSome(File path, int limit)
			throws FileNotFoundException, IOException {
		try (SilentFileInputStream in = new SilentFileInputStream(path)) {
			byte[] buf = new byte[limit];
			int cnt = 0;
			for (;;) {
				int n = in.read(buf, cnt, buf.length - cnt);
				if (n <= 0)
					break;
				cnt += n;
			}
			if (cnt == buf.length)
				return buf;
			byte[] res = new byte[cnt];
			System.arraycopy(buf, 0, res, 0, cnt);
			return res;
		}
	}

	
Read an entire local file into memory as a byte array.
Params:
path – 
           location of the file to read.
max – 
           maximum number of bytes to read, if the file is larger than
           this limit an IOException is thrown.
Throws:
FileNotFoundException – 
            the file does not exist.
IOException – 
            the file exists, but its contents cannot be read.
Returns:
complete contents of the requested local file./**
	 * Read an entire local file into memory as a byte array.
	 *
	 * @param path
	 *            location of the file to read.
	 * @param max
	 *            maximum number of bytes to read, if the file is larger than
	 *            this limit an IOException is thrown.
	 * @return complete contents of the requested local file.
	 * @throws java.io.FileNotFoundException
	 *             the file does not exist.
	 * @throws java.io.IOException
	 *             the file exists, but its contents cannot be read.
	 */
	public static final byte[] readFully(File path, int max)
			throws FileNotFoundException, IOException {
		try (SilentFileInputStream in = new SilentFileInputStream(path)) {
			long sz = Math.max(path.length(), 1);
			if (sz > max)
				throw new IOException(MessageFormat.format(
						JGitText.get().fileIsTooLarge, path));

			byte[] buf = new byte[(int) sz];
			int valid = 0;
			for (;;) {
				if (buf.length == valid) {
					if (buf.length == max) {
						int next = in.read();
						if (next < 0)
							break;

						throw new IOException(MessageFormat.format(
								JGitText.get().fileIsTooLarge, path));
					}

					byte[] nb = new byte[Math.min(buf.length * 2, max)];
					System.arraycopy(buf, 0, nb, 0, valid);
					buf = nb;
				}
				int n = in.read(buf, valid, buf.length - valid);
				if (n < 0)
					break;
				valid += n;
			}
			if (valid < buf.length) {
				byte[] nb = new byte[valid];
				System.arraycopy(buf, 0, nb, 0, valid);
				buf = nb;
			}
			return buf;
		}
	}

	
Read an entire input stream into memory as a ByteBuffer.
Note: The stream is read to its end and is not usable after calling this
method. The caller is responsible for closing the stream.
Params:
in – 
           input stream to be read.
sizeHint – 
           a hint on the approximate number of bytes contained in the
           stream, used to allocate temporary buffers more efficiently
Throws:
IOException – 
            there was an error reading from the stream.
Returns:
complete contents of the input stream. The ByteBuffer always has a writable backing array, with position() == 0 and limit() equal to the actual length read. Callers may rely on obtaining the underlying array for efficient data access. If sizeHint was too large, the array may be over-allocated, resulting in limit() < array().length./**
	 * Read an entire input stream into memory as a ByteBuffer.
	 *
	 * Note: The stream is read to its end and is not usable after calling this
	 * method. The caller is responsible for closing the stream.
	 *
	 * @param in
	 *            input stream to be read.
	 * @param sizeHint
	 *            a hint on the approximate number of bytes contained in the
	 *            stream, used to allocate temporary buffers more efficiently
	 * @return complete contents of the input stream. The ByteBuffer always has
	 *         a writable backing array, with {@code position() == 0} and
	 *         {@code limit()} equal to the actual length read. Callers may rely
	 *         on obtaining the underlying array for efficient data access. If
	 *         {@code sizeHint} was too large, the array may be over-allocated,
	 *         resulting in {@code limit() < array().length}.
	 * @throws java.io.IOException
	 *             there was an error reading from the stream.
	 */
	public static ByteBuffer readWholeStream(InputStream in, int sizeHint)
			throws IOException {
		byte[] out = new byte[sizeHint];
		int pos = 0;
		while (pos < out.length) {
			int read = in.read(out, pos, out.length - pos);
			if (read < 0)
				return ByteBuffer.wrap(out, 0, pos);
			pos += read;
		}

		int last = in.read();
		if (last < 0)
			return ByteBuffer.wrap(out, 0, pos);

		try (TemporaryBuffer.Heap tmp = new TemporaryBuffer.Heap(
				Integer.MAX_VALUE)) {
			tmp.write(out);
			tmp.write(last);
			tmp.copy(in);
			return ByteBuffer.wrap(tmp.toByteArray());
		}
	}

	
Read the entire byte array into memory, or throw an exception.
Params:
fd – 
           input stream to read the data from.
dst – 
           buffer that must be fully populated, [off, off+len).
off – 
           position within the buffer to start writing to.
len – 
           number of bytes that must be read.
Throws:
EOFException – 
            the stream ended before dst was fully populated.
IOException – 
            there was an error reading from the stream./**
	 * Read the entire byte array into memory, or throw an exception.
	 *
	 * @param fd
	 *            input stream to read the data from.
	 * @param dst
	 *            buffer that must be fully populated, [off, off+len).
	 * @param off
	 *            position within the buffer to start writing to.
	 * @param len
	 *            number of bytes that must be read.
	 * @throws EOFException
	 *             the stream ended before dst was fully populated.
	 * @throws java.io.IOException
	 *             there was an error reading from the stream.
	 */
	public static void readFully(final InputStream fd, final byte[] dst,
			int off, int len) throws IOException {
		while (len > 0) {
			final int r = fd.read(dst, off, len);
			if (r <= 0)
				throw new EOFException(JGitText.get().shortReadOfBlock);
			off += r;
			len -= r;
		}
	}

	
Read as much of the array as possible from a channel.
Params:
channel – 
           channel to read data from.
dst – 
           buffer that must be fully populated, [off, off+len).
off – 
           position within the buffer to start writing to.
len – 
           number of bytes that should be read.
Throws:
IOException – 
            there was an error reading from the channel.
Returns:
number of bytes actually read./**
	 * Read as much of the array as possible from a channel.
	 *
	 * @param channel
	 *            channel to read data from.
	 * @param dst
	 *            buffer that must be fully populated, [off, off+len).
	 * @param off
	 *            position within the buffer to start writing to.
	 * @param len
	 *            number of bytes that should be read.
	 * @return number of bytes actually read.
	 * @throws java.io.IOException
	 *             there was an error reading from the channel.
	 */
	public static int read(ReadableByteChannel channel, byte[] dst, int off,
			int len) throws IOException {
		if (len == 0)
			return 0;
		int cnt = 0;
		while (0 < len) {
			int r = channel.read(ByteBuffer.wrap(dst, off, len));
			if (r <= 0)
				break;
			off += r;
			len -= r;
			cnt += r;
		}
		return cnt != 0 ? cnt : -1;
	}

	
Read the entire byte array into memory, unless input is shorter
Params:
fd – 
           input stream to read the data from.
dst – 
           buffer that must be fully populated, [off, off+len).
off – 
           position within the buffer to start writing to.
Throws:
IOException – 
            there was an error reading from the stream.
Returns:
number of bytes in buffer or stream, whichever is shortest/**
	 * Read the entire byte array into memory, unless input is shorter
	 *
	 * @param fd
	 *            input stream to read the data from.
	 * @param dst
	 *            buffer that must be fully populated, [off, off+len).
	 * @param off
	 *            position within the buffer to start writing to.
	 * @return number of bytes in buffer or stream, whichever is shortest
	 * @throws java.io.IOException
	 *             there was an error reading from the stream.
	 */
	public static int readFully(InputStream fd, byte[] dst, int off)
			throws IOException {
		int r;
		int len = 0;
		while ((r = fd.read(dst, off, dst.length - off)) >= 0
				&& len < dst.length) {
			off += r;
			len += r;
		}
		return len;
	}

	
Skip an entire region of an input stream.

The input stream's position is moved forward by the number of requested
bytes, discarding them from the input. This method does not return until
the exact number of bytes requested has been skipped.
Params:
fd – 
           the stream to skip bytes from.
toSkip – 
           total number of bytes to be discarded. Must be >= 0.
Throws:
EOFException – 
            the stream ended before the requested number of bytes were
            skipped.
IOException – 
            there was an error reading from the stream./**
	 * Skip an entire region of an input stream.
	 * <p>
	 * The input stream's position is moved forward by the number of requested
	 * bytes, discarding them from the input. This method does not return until
	 * the exact number of bytes requested has been skipped.
	 *
	 * @param fd
	 *            the stream to skip bytes from.
	 * @param toSkip
	 *            total number of bytes to be discarded. Must be &gt;= 0.
	 * @throws EOFException
	 *             the stream ended before the requested number of bytes were
	 *             skipped.
	 * @throws java.io.IOException
	 *             there was an error reading from the stream.
	 */
	public static void skipFully(InputStream fd, long toSkip)
			throws IOException {
		while (toSkip > 0) {
			final long r = fd.skip(toSkip);
			if (r <= 0)
				throw new EOFException(JGitText.get().shortSkipOfBlock);
			toSkip -= r;
		}
	}

	
Divides the given string into lines.
Params:
s – 
           the string to read
Returns:
the string divided into lines
Since:
2.0/**
	 * Divides the given string into lines.
	 *
	 * @param s
	 *            the string to read
	 * @return the string divided into lines
	 * @since 2.0
	 */
	public static List<String> readLines(String s) {
		List<String> l = new ArrayList<>();
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);
			if (c == '\n') {
				l.add(sb.toString());
				sb.setLength(0);
				continue;
			}
			if (c == '\r') {
				if (i + 1 < s.length()) {
					c = s.charAt(++i);
					l.add(sb.toString());
					sb.setLength(0);
					if (c != '\n') {
						sb.append(c);
					}
					continue;
				}
				// EOF
				l.add(sb.toString());
				break;
			}
			sb.append(c);
		}
		l.add(sb.toString());
		return l;
	}

	
Read the next line from a reader.
 Like BufferedReader.readLine(), but only treats \n as end-of-line, and includes the trailing newline. 
Params:
in – 
           the reader to read from.
sizeHint – 
           hint for buffer sizing; 0 or negative for default.
Throws:
IOException – 
            there was an error reading from the stream.
Returns:
the next line from the input, always ending in \n unless EOF was reached.
Since:
4.1/**
	 * Read the next line from a reader.
	 * <p>
	 * Like {@link java.io.BufferedReader#readLine()}, but only treats
	 * {@code \n} as end-of-line, and includes the trailing newline.
	 *
	 * @param in
	 *            the reader to read from.
	 * @param sizeHint
	 *            hint for buffer sizing; 0 or negative for default.
	 * @return the next line from the input, always ending in {@code \n} unless
	 *         EOF was reached.
	 * @throws java.io.IOException
	 *             there was an error reading from the stream.
	 * @since 4.1
	 */
	public static String readLine(Reader in, int sizeHint) throws IOException {
		if (in.markSupported()) {
			if (sizeHint <= 0) {
				sizeHint = 1024;
			}
			StringBuilder sb = new StringBuilder(sizeHint);
			char[] buf = new char[sizeHint];
			while (true) {
				in.mark(sizeHint);
				int n = in.read(buf);
				if (n < 0) {
					in.reset();
					return sb.toString();
				}
				for (int i = 0; i < n; i++) {
					if (buf[i] == '\n') {
						resetAndSkipFully(in, ++i);
						sb.append(buf, 0, i);
						return sb.toString();
					}
				}
				if (n > 0) {
					sb.append(buf, 0, n);
				}
				resetAndSkipFully(in, n);
			}
		}
		StringBuilder buf = sizeHint > 0 ? new StringBuilder(sizeHint)
				: new StringBuilder();
		int i;
		while ((i = in.read()) != -1) {
			char c = (char) i;
			buf.append(c);
			if (c == '\n') {
				break;
			}
		}
		return buf.toString();
	}

	private static void resetAndSkipFully(Reader fd, long toSkip) throws IOException {
		fd.reset();
		while (toSkip > 0) {
			long r = fd.skip(toSkip);
			if (r <= 0) {
				throw new EOFException(JGitText.get().shortSkipOfBlock);
			}
			toSkip -= r;
		}
	}

	private IO() {
		// Don't create instances of a static only utility.
	}
}