/*
    * Copyright (C) 2012, Google Inc.
    * 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
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   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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  package org.eclipse.jgit.http.server;
  
  import static org.eclipse.jgit.http.server.ServletUtils.isChunked;
  
  import javax.servlet.http.HttpServletRequest;
  
  /**
   * Parses Git client User-Agent strings.
   */
  public class ClientVersionUtil {
  	private static final int[] v1_7_5 = { 1, 7, 5 };
  	private static final int[] v1_7_8_6 = { 1, 7, 8, 6 };
  	private static final int[] v1_7_9 = { 1, 7, 9 };
  
  	/**
  	 * An invalid version of Git
  	 *
  	 * @return maximum version array, indicating an invalid version of Git.
  	 */
  	public static int[] invalidVersion() {
  		return new int[] { Integer.MAX_VALUE };
  	}
  
  	/**
  	 * Parse a Git client User-Agent header value.
  	 *
  	 * @param version
  	 *            git client version string, of the form "git/1.7.9".
  	 * @return components of the version string. {@link #invalidVersion()} if
  	 *         the version string cannot be parsed.
  	 */
  	public static int[] parseVersion(String version) {
  		if (version != null && version.startsWith("git/"))
  			return splitVersion(version.substring("git/".length()));
  		return invalidVersion();
  	}
  
  	private static int[] splitVersion(String versionString) {
  		char[] str = versionString.toCharArray();
  		int[] ver = new int[4];
  		int end = 0;
  		int acc = 0;
  		for (int i = 0; i < str.length; i++) {
  			char c = str[i];
  			if ('0' <= c && c <= '9') {
  				acc *= 10;
  				acc += c - '0';
  			} else if (c == '.') {
  				if (end == ver.length)
  					ver = grow(ver);
  				ver[end++] = acc;
  				acc = 0;
  			} else if (c == 'g' && 0 < i && str[i - 1] == '.' && 0 < end) {
  				// Non-tagged builds may contain a mangled git describe output.
  				// "1.7.6.1.45.gbe0cc". The 45 isn't a valid component. Drop it.
  				ver[end - 1] = 0;
 				acc = 0;
 				break;
 			} else if (c == '-' && (i + 2) < str.length
 					&& str[i + 1] == 'r' && str[i + 2] == 'c') {
 				// Release candidates aren't the same as a final release.
 				if (acc > 0)
 					acc--;
 				break;
 			} else
 				break;
 		}
 		if (acc != 0) {
 			if (end == ver.length)
 				ver = grow(ver);
 			ver[end++] = acc;
 		} else {
 			while (0 < end && ver[end - 1] == 0)
 				end--;
 		}
 		if (end < ver.length) {
 			int[] n = new int[end];
 			System.arraycopy(ver, 0, n, 0, end);
 			ver = n;
 		}
 		return ver;
 	}
 
 	private static int[] grow(int[] tmp) {
 		int[] n = new int[tmp.length + 1];
 		System.arraycopy(tmp, 0, n, 0, tmp.length);
 		return n;
 	}
 
 	/**
 	 * Compare two version strings for natural ordering.
 	 *
 	 * @param a
 	 *            first parsed version string.
 	 * @param b
 	 *            second parsed version string.
 	 * @return &lt; 0 if a is before b; 0 if a equals b; &gt;0 if a is after b.
 	 */
 	public static int compare(int[] a, int[] b) {
 		for (int i = 0; i < a.length && i < b.length; i++) {
 			int cmp = a[i] - b[i];
 			if (cmp != 0)
 				return cmp;
 		}
 		return a.length - b.length;
 	}
 
 	/**
 	 * Convert a parsed version back to a string.
 	 *
 	 * @param ver
 	 *            the parsed version array.
 	 * @return a string, e.g. "1.6.6.0".
 	 */
 	public static String toString(int[] ver) {
 		StringBuilder b = new StringBuilder();
 		for (int v : ver) {
 			if (b.length() > 0)
 				b.append('.');
 			b.append(v);
 		}
 		return b.toString();
 	}
 
 	/**
 	 * Check if a Git client has the known push status bug.
 	 * <p>
 	 * These buggy clients do not display the status report from a failed push
 	 * over HTTP.
 	 *
 	 * @param version
 	 *            parsed version of the Git client software.
 	 * @return true if the bug is present.
 	 */
 	public static boolean hasPushStatusBug(int[] version) {
 		int cmp = compare(version, v1_7_8_6);
 		if (cmp < 0)
 			return true; // Everything before 1.7.8.6 is known broken.
 		else if (cmp == 0)
 			return false; // 1.7.8.6 contained the bug fix.
 
 		if (compare(version, v1_7_9) <= 0)
 			return true; // 1.7.9 shipped before 1.7.8.6 and has the bug.
 		return false; // 1.7.9.1 and later are fixed.
 	}
 
 	/**
 	 * Check if a Git client has the known chunked request body encoding bug.
 	 * <p>
 	 * Git 1.7.5 contains a unique bug where chunked requests are malformed.
 	 * This applies to both fetch and push.
 	 *
 	 * @param version
 	 *            parsed version of the Git client software.
 	 * @param request
 	 *            incoming HTTP request.
 	 * @return true if the client has the chunked encoding bug.
 	 */
 	public static boolean hasChunkedEncodingRequestBug(
 			int[] version, HttpServletRequest request) {
 		return compare(version, v1_7_5) == 0 && isChunked(request);
 	}
 
 	private ClientVersionUtil() {
 	}
 }