## Copyright (C) 2005-2012 Søren Hauberg
##
## 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} {} doc @var{function_name}
## Display documentation for the function @var{function_name}
## directly from an online version of
## the printed manual, using the GNU Info browser.  If invoked without
## any arguments, the manual is shown from the beginning.
##
## For example, the command @kbd{doc rand} starts the GNU Info browser
## at the @code{rand} node in the online version of the manual.
##
## Once the GNU Info browser is running, help for using it is available
## using the command @kbd{C-h}.
## @seealso{help}
## @end deftypefn

## Author: Soren Hauberg <soren@hauberg.org>
## Adapted-by: jwe

function retval = doc (fname)

  if (nargin == 0 || nargin == 1)

    ftype = 0;

    if (nargin == 1)
      ## Get the directory where the function lives.
      ## FIXME -- maybe we should have a better way of doing this.

      if (ischar (fname))
        ftype = exist (fname);
      else
        error ("doc: expecting argument to be a character string");
      endif
    else
      fname = "";
    endif

    if (ftype == 2 || ftype == 3)
      ffile = which (fname);
    else
      ffile = "";
    endif

    if (isempty (ffile))
      info_dir = octave_config_info ("infodir");
    else
      info_dir = fileparts (ffile);
    endif

    ## Determine if a file called doc.info exist in the same
    ## directory as the function.

    info_file_name = fullfile (info_dir, "doc.info");

    [stat_info, err] = stat (info_file_name);

    if (err < 0)
      info_file_name = info_file ();
    endif

    ## FIXME -- don't change the order of the arguments below because
    ## the info-emacs-info script currently expects --directory DIR as
    ## the third and fourth arguments.  Someone should fix that.

    cmd = sprintf ("\"%s\" --file \"%s\" --directory \"%s\"",
                   info_program (), info_file_name, info_dir);

    have_fname = ! isempty (fname);

    if (have_fname)
      status = system (sprintf ("%s --index-search %s", cmd, fname));
    endif

    if (! (have_fname && status == 0))
      status = system (cmd);
      if (status == 127)
        warning ("unable to find info program '%s'", info_program ());
      endif
    endif

    if (nargout > 0)
      retval = status;
    endif

  else
    print_usage ();
  endif

endfunction

%!test if exist( info_file ()) != 2 && exist (sprintf ("%s.gz", info_file ())) != 2
%!       error ("Info file %s or %s.gz does not exist!", info_file (), info_file ());
%!     endif
