/*
    * Copyright (C) 2009, Google Inc.
    * Copyright (C) 2008-2009, Johannes E. Schindelin <johannes.schindelin@gmx.de>
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above
   *   copyright notice, this list of conditions and the following
   *   disclaimer in the documentation and/or other materials provided
   *   with the distribution.
   *
   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
   *   products derived from this software without specific prior
   *   written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package org.eclipse.jgit.diff;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  
  import org.eclipse.jgit.util.IO;
  import org.eclipse.jgit.util.IntList;
  import org.eclipse.jgit.util.RawParseUtils;
  
  /**
   * A Sequence supporting UNIX formatted text in byte[] format.
   * <p>
   * Elements of the sequence are the lines of the file, as delimited by the UNIX
   * newline character ('\n'). The file content is treated as 8 bit binary text,
   * with no assumptions or requirements on character encoding.
   * <p>
   * Note that the first line of the file is element 0, as defined by the Sequence
   * interface API. Traditionally in a text editor a patch file the first line is
   * line number 1. Callers may need to subtract 1 prior to invoking methods if
   * they are converting from "line number" to "element index".
   */
  public class RawText extends Sequence {
  	/** A Rawtext of length 0 */
  	public static final RawText EMPTY_TEXT = new RawText(new byte[0]);
  
  	/** Number of bytes to check for heuristics in {@link #isBinary(byte[])} */
  	private static final int FIRST_FEW_BYTES = 8000;
  
  	/** The file content for this sequence. */
  	protected final byte[] content;
  
  	/** Map of line number to starting position within {@link #content}. */
  	protected final IntList lines;
  
  	/**
  	 * Create a new sequence from an existing content byte array.
  	 * <p>
  	 * The entire array (indexes 0 through length-1) is used as the content.
  	 *
  	 * @param input
  	 *            the content array. The array is never modified, so passing
  	 *            through cached arrays is safe.
  	 */
  	public RawText(final byte[] input) {
  		content = input;
  		lines = RawParseUtils.lineMap(content, 0, content.length);
  	}
  
  	/**
  	 * Create a new sequence from a file.
  	 * <p>
  	 * The entire file contents are used.
  	 *
 	 * @param file
 	 *            the text file.
 	 * @throws IOException
 	 *             if Exceptions occur while reading the file
 	 */
 	public RawText(File file) throws IOException {
 		this(IO.readFully(file));
 	}
 
 	/** @return total number of items in the sequence. */
 	public int size() {
 		// The line map is always 2 entries larger than the number of lines in
 		// the file. Index 0 is padded out/unused. The last index is the total
 		// length of the buffer, and acts as a sentinel.
 		//
 		return lines.size() - 2;
 	}
 
 	/**
 	 * Write a specific line to the output stream, without its trailing LF.
 	 * <p>
 	 * The specified line is copied as-is, with no character encoding
 	 * translation performed.
 	 * <p>
 	 * If the specified line ends with an LF ('\n'), the LF is <b>not</b>
 	 * copied. It is up to the caller to write the LF, if desired, between
 	 * output lines.
 	 *
 	 * @param out
 	 *            stream to copy the line data onto.
 	 * @param i
 	 *            index of the line to extract. Note this is 0-based, so line
 	 *            number 1 is actually index 0.
 	 * @throws IOException
 	 *             the stream write operation failed.
 	 */
 	public void writeLine(final OutputStream out, final int i)
 			throws IOException {
 		int start = getStart(i);
 		int end = getEnd(i);
 		if (content[end - 1] == '\n')
 			end--;
 		out.write(content, start, end - start);
 	}
 
 	/**
 	 * Determine if the file ends with a LF ('\n').
 	 *
 	 * @return true if the last line has an LF; false otherwise.
 	 */
 	public boolean isMissingNewlineAtEnd() {
 		final int end = lines.get(lines.size() - 1);
 		if (end == 0)
 			return true;
 		return content[end - 1] != '\n';
 	}
 
 	/**
 	 * Get the text for a single line.
 	 *
 	 * @param i
 	 *            index of the line to extract. Note this is 0-based, so line
 	 *            number 1 is actually index 0.
 	 * @return the text for the line, without a trailing LF.
 	 */
 	public String getString(int i) {
 		return getString(i, i + 1, true);
 	}
 
 	/**
 	 * Get the text for a region of lines.
 	 *
 	 * @param begin
 	 *            index of the first line to extract. Note this is 0-based, so
 	 *            line number 1 is actually index 0.
 	 * @param end
 	 *            index of one past the last line to extract.
 	 * @param dropLF
 	 *            if true the trailing LF ('\n') of the last returned line is
 	 *            dropped, if present.
 	 * @return the text for lines {@code [begin, end)}.
 	 */
 	public String getString(int begin, int end, boolean dropLF) {
 		if (begin == end)
 			return ""; //$NON-NLS-1$
 
 		int s = getStart(begin);
 		int e = getEnd(end - 1);
 		if (dropLF && content[e - 1] == '\n')
 			e--;
 		return decode(s, e);
 	}
 
 	/**
 	 * Decode a region of the text into a String.
 	 *
 	 * The default implementation of this method tries to guess the character
 	 * set by considering UTF-8, the platform default, and falling back on
 	 * ISO-8859-1 if neither of those can correctly decode the region given.
 	 *
 	 * @param start
 	 *            first byte of the content to decode.
 	 * @param end
 	 *            one past the last byte of the content to decode.
 	 * @return the region {@code [start, end)} decoded as a String.
 	 */
 	protected String decode(int start, int end) {
 		return RawParseUtils.decode(content, start, end);
 	}
 
 	private int getStart(final int i) {
 		return lines.get(i + 1);
 	}
 
 	private int getEnd(final int i) {
 		return lines.get(i + 2);
 	}
 
 	/**
 	 * Determine heuristically whether a byte array represents binary (as
 	 * opposed to text) content.
 	 *
 	 * @param raw
 	 *            the raw file content.
 	 * @return true if raw is likely to be a binary file, false otherwise
 	 */
 	public static boolean isBinary(byte[] raw) {
 		return isBinary(raw, raw.length);
 	}
 
 	/**
 	 * Determine heuristically whether the bytes contained in a stream
 	 * represents binary (as opposed to text) content.
 	 *
 	 * Note: Do not further use this stream after having called this method! The
 	 * stream may not be fully read and will be left at an unknown position
 	 * after consuming an unknown number of bytes. The caller is responsible for
 	 * closing the stream.
 	 *
 	 * @param raw
 	 *            input stream containing the raw file content.
 	 * @return true if raw is likely to be a binary file, false otherwise
 	 * @throws IOException
 	 *             if input stream could not be read
 	 */
 	public static boolean isBinary(InputStream raw) throws IOException {
 		final byte[] buffer = new byte[FIRST_FEW_BYTES];
 		int cnt = 0;
 		while (cnt < buffer.length) {
 			final int n = raw.read(buffer, cnt, buffer.length - cnt);
 			if (n == -1)
 				break;
 			cnt += n;
 		}
 		return isBinary(buffer, cnt);
 	}
 
 	/**
 	 * Determine heuristically whether a byte array represents binary (as
 	 * opposed to text) content.
 	 *
 	 * @param raw
 	 *            the raw file content.
 	 * @param length
 	 *            number of bytes in {@code raw} to evaluate. This should be
 	 *            {@code raw.length} unless {@code raw} was over-allocated by
 	 *            the caller.
 	 * @return true if raw is likely to be a binary file, false otherwise
 	 */
 	public static boolean isBinary(byte[] raw, int length) {
 		// Same heuristic as C Git
 		if (length > FIRST_FEW_BYTES)
 			length = FIRST_FEW_BYTES;
 		for (int ptr = 0; ptr < length; ptr++)
 			if (raw[ptr] == '\0')
 				return true;
 
 		return false;
 	}
 
 	/**
 	 * Get the line delimiter for the first line.
 	 *
 	 * @since 2.0
 	 * @return the line delimiter or <code>null</code>
 	 */
 	public String getLineDelimiter() {
 		if (size() == 0)
 			return null;
 		int e = getEnd(0);
 		if (content[e - 1] != '\n')
 			return null;
 		if (content.length > 1 && e > 1 && content[e - 2] == '\r')
 			return "\r\n"; //$NON-NLS-1$
 		else
 			return "\n"; //$NON-NLS-1$
 	}
 }