## Copyright (C) 2005, 2006, 2007 William Poetra Yoga Hadisoeseno
##
## This file is part of Octave.
##
## Octave 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 3 of the License, or (at
## your option) any later version.
##
## Octave 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 Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} license
## Display the license of Octave.
##
## @deftypefnx {Function File} {} license ("inuse")
## Display a list of packages currently being used.
##
## @deftypefnx {Function File} {@var{retval} =} license ("inuse")
## Return a structure containing the fields @code{feature} and @code{user}.
##
## @deftypefnx {Function File} {@var{retval} =} license ("test", @var{feature})
## Return 1 if a license exists for the product identified by the string
## @var{feature} and 0 otherwise.  The argument @var{feature} is case
## insensitive and only the first 27 characters are checked.
##
## @deftypefnx {Function File} {} license ("test", @var{feature}, @var{toggle})
## Enable or disable license testing for @var{feature}, depending on
## @var{toggle}, which may be one of:
##
## @table @samp
## @item "enable"
## Future tests for the specified license of @var{feature} are conducted
## as usual.
## @item "disable"
## Future tests for the specified license of @var{feature} return 0.
## @end table
##
## @deftypefnx {Function File} {@var{retval} =} license ("checkout", @var{feature})
## Check out a license for @var{feature}, returning 1 on success and 0
## on failure.
##
## This function is provided for compatibility with @sc{matlab}.
## @seealso{ver, version}
## @end deftypefn

## Author: William Poetra Yoga Hadisoeseno <williampoetra@gmail.com>

function retval = license (varargin)

  persistent __octave_licenses__;

  if (isempty (__octave_licenses__))
    __octave_licenses__ = cell ();
    __octave_licenses__{1,1} = "Octave";
    __octave_licenses__{1,2} = "GNU General Public License";
    __octave_licenses__{1,3} = true;
    if (exist ("OCTAVE_FORGE_VERSION"))
      __octave_licenses__{2,1} = "octave-forge";
      __octave_licenses__{2,2} = "<various licenses>";
      __octave_licenses__{2,3} = true;
    endif
  endif

  nout = nargout;
  nin = nargin;
  nr_licenses = rows (__octave_licenses__);

  if (nout > 1 || nin > 3)
    error ("type `help license' for usage info");
  endif

  if (nin == 0)

    found = false;
    for p = 1:nr_licenses
      if (strcmp (__octave_licenses__{p,1}, "Octave"))
        found = true;
        break;
      endif
    endfor

    if (found)
      result = __octave_licenses__{p,2};
    else
      result = "unknown";
    endif

    if (nout == 0)
      printf ("%s\n", result);
    else
      retval = result;
    endif

  elseif (nin == 1)

    if (nout == 0)

      if (! strcmp (varargin{1}, "inuse"))
        usage ("license (\"inuse\")");
      endif

      for p = 1:nr_licenses
        printf ("%s\n", __octave_licenses__{p,1});
      endfor

    else

      if (! strcmp (varargin{1}, "inuse"))
        usage ("retval = license (\"inuse\")");
      endif

      pw = getpwuid (getuid ());
      if (isstruct (pw))
	username = pw.name;
      else
	username = "octave_user";
      endif

      retval(1:nr_licenses) = struct ("feature", "", "user", "");
      for p = 1:nr_licenses
        retval(p).feature = __octave_licenses__{p,1};
        retval(p).user = username;
      endfor

    endif

  else

    feature = varargin{2}(1:(min ([(length (varargin{2})), 27])));

    if (strcmp (varargin{1}, "test"))

      found = false;
      for p = 1:nr_licenses
        if (strcmpi (feature, __octave_licenses__{p,1}))
          found = true;
          break;
        endif
      endfor

      if (nin == 2)
        retval = found && __octave_licenses__{p,3};
      else
        if (found)
          if (strcmp (varargin{3}, "enable"))
            __octave_licenses__{p,3} = true;
          elseif (strcmp (varargin{3}, "disable"))
            __octave_licenses__{p,3} = false;
          else
            error ("toggle must be either `enable' of `disable'");
          endif
        else
          error ("feature `%s' not found", feature);
        endif
      endif

    elseif (strcmp (varargin{1}, "checkout"))

      if (nin != 2)
        usage ("retval = license (\"checkout\", feature)");
      endif

      found = false;
      for p = 1:nr_licenses
        if (strcmpi (feature, __octave_licenses__{p,1}))
          found = true;
          break;
        endif
      endfor

      retval = found && __octave_licenses__{p,3};

    else

      error ("type `help license' for usage info");

    endif

  endif

endfunction