## Copyright (C) 2013 Júlio Hoffimann
## Copyright (C) 2013 Carnë Draug
##
## 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  {Command} {} citation
## @deftypefnx {Command} {} citation @var{pkgname}
## @deftypefnx {Function File} {} citation (@var{pkgname}, @var{reference})
## Display citation to use for GNU Octave or installed package.
##
##
##
## The 2 arguments function is meant for developers.  It allows for a package
## to register the displayed @var{reference} for a specific @var{pkgname}.  To
## unregister, an empty reference can be used.  These should be used in
## conjunction with the @code{PKG_ADD} and @code{PKG_DEL}
##
## @seealso{info, version}
## @end deftypefn

function citation (pkgname = "octave", reference)

  persistent ref_list = struct ("octave", core_reference ());

  if (nargin > 2)
    print_usage();
  elseif (! ischar (pkgname))
    error ("citation: PKGNAME must be a string");
  endif

  pkgname = tolower (pkgname);
  if (nargin == 0 || nargin == 1)
    if (isfield (ref_list, pkgname))
      disp (ref_list.(pkgname));
    else
      printf ("No citation found for %s\n", pkgname);
    endif

  elseif (nargin == 2)
    if (! ischar (reference))
      error ("citation: REFERENCE to use for package %s must be a string", pkgname);
    elseif (strcmpi (pkgname, "octave"))
      error ("citation: not allowed to overwrite citation for GNU Octave");
    elseif (isempty (reference))
      ref_list = rmfield (ref_list, pkgname);
    else
      ref_list.(pkgname) = reference;
    endif
  endif

endfunction

function ref = core_reference
  ref = "\n...
To cite GNU Octave in publications use:\n...
\n...
  John W. Eaton, David Bateman, and Soren Hauberg.\n...
  Gnu Octave Version 3.0.1 Manual: A High-Level Interactive Language For\n...
  Numerical Computations. CreateSpace Independent Publishing Platform, 2009.\n...
  ISBN 1441413006. URL http://www.gnu.org/software/octave/doc/interpreter/.\n...
\n...
A BibTeX entry for LaTeX users is\n...
\n...
@book{\n...
  Author    = {John W. Eaton and David Bateman and S\\o ren Hauberg},\n...
  Title     = {Gnu Octave Version 3.0.1 Manual: A High-Level Interactive Language For Numerical Computations},\n...
  Publisher = {CreateSpace Independent Publishing Platform},\n...
  Year      = {2009},\n...
  ISBN      = {1441413006},\n...
  URL       = {http://www.gnu.org/software/octave/doc/interpreter},\n...
}\n...
\n...
See also `citation pkgname' for citing GNU Octave packages.";
endfunction

%!assert (~isempty (citation ()))
