## Copyright (C) 2006 Soren Hauberg
## 
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
## 
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
## 
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

## -*- texinfo -*-
## @deftypefn {Function File} {} compare_version (@var{v1}, @var{v2})
## Compares two version strings, returning 0 if they are equal, 1 if
## @var{v1} is larger (i.e. more recent) than @var{v2}, and -1 otherwise.
##
## A version string is a string that describes the version of a piece of
## software. This function supports the most common type of version strings 
## found in Free Software, i.e. "Major.Minor.Revision-Text". In this format
## Minor, Revision and Text are optional, but for clarity it is recommended
## to at least provide Minor and Revision. If Minor or Revision is not 
## given, they default to 0, while Text defaults to the empty string. Hence
## the following is true,
## @example
## 2.6 == 2.6.0 < 2.6.0-SVN < 2.6.1
## @end example
## @end deftypefn

function [ ret ] = compare_version (v1, v2)
  ## Both arguments must be strings
  if (!ischar(v1) || !ischar(v2))
      error("compare_version: Both input arguments must be strings.");
  endif
  
  ## Split the strings into parts X.Y.Z-TEXT
  [major1, minor1, rev1, text1] = get_parts(v1);
  [major2, minor2, rev2, text2] = get_parts(v2);
  
  ## Gentleman, start your comparing...
  major = sign(major1 - major2);
  minor = sign(minor1 - minor2);
  rev = sign(rev1 - rev2);
  text = !strcmp(text1, text2); % XXX: This is just plain wrong! (But it'll have to do for now!)
  
  if (major != 0)
      ret = major;
  elseif (minor != 0)
      ret = minor;
  elseif (rev != 0)
      ret = rev;
  else
      ret = text;
  endif
endfunction

## Splits a version string into Major.Minor.Revision-Text.
## Minor and Revision defaults to 0 ,while Text defaults to the empty string.
function [major, minor, revision, text] = get_parts(v)
  ## Default values
  minor = revision = 0;
  text = "";

  ## Get text
  dash = find(v == "-");
  if (length(dash) > 0)
      text = v(dash(1)+1:end);
      v = v(1:dash(1)-1);
  endif
  
  ## Get major, minor, and revision
  dots = [find(v == "."), length(v)+1];
  major = str2num( v(1:dots(1)-1) );
  if (length(dots) >= 2)
      minor = str2num( v( dots(1)+1:dots(2)-1 ) );
  endif
  if (length(dots) >= 3)
      revision = str2num( v( dots(2)+1:dots(3)-1 ) );
  endif
  
  ## Is everything okay?
  if ( isempty(major) || isempty(minor) || isempty(revision) )
      error("Input argument is not a valid version string.");
  endif
endfunction

%!test 
%! if (compare_version("2.6.1", "2.6.0") != 1) 
%!     error("Test 1");
%! endif

%!test 
%! if (compare_version("2.6", "2.6.0") != 0) 
%!     error("Test 2");
%! endif

%!test
%! if (compare_version("2.6-SVN", "2.6.0") != 1)
%!     error("Test 3");
%! endif

## XXX: Is there a more easy way to test that a function returns an error?
%!test
%! test_failed = true;
%! try
%!     compare_version("2.6.0", "Monkey");
%! catch
%!     test_failed = false;
%! end_try_catch
%! if (test_failed)
%!     error("Test 4");
%! endif

%!test
%! if (compare_version("2.6.0-SVN2", "2.6.0-SVN1"))
%!     error("Test 5");
%! endif