## Copyright (C) 2012 Rik Wehbring
## Parts Copyright (C) 2012 Philip Nienhuis <prnienhuis@users.sf.net>
##
## 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} {} usejava (@var{feature})
## Return true if the Java element @var{feature} is available.
##
## Possible features are:
##
## @table @asis
## @item "awt"
## Abstract Window Toolkit for GUIs.
##
## @item "desktop"
## Interactive desktop is running.
##
## @item "jvm"
## Java Virtual Machine.
##
## @item "swing"
## Swing components for lightweight GUIs.
## @end table
##
## @code{usejava} determines if specific Java features are available in an
## Octave session.  This function is provided for compatibility with scripts
## which may alter their behavior based on the availability of Java.  The
## feature "desktop" always returns @code{false} as Octave has no Java-based
## desktop.  Other features may be available if the Octave-Forge Java package
## has been installed.
## @end deftypefn

function retval = usejava (feature)

  if (nargin != 1 || ! ischar (feature))
    print_usage ();
  endif

  retval = false;

  switch feature
    ## For each feature, try javamethods() on a Java class of a feature
    case "awt"
      try
        dum = javamethods ("java.awt.Frame");
        retval = true;
      end_try_catch
    case "desktop"
      ## Octave has no Java based GUI/desktop, leave retval = false
    case "jvm"
      try
        dum = javamethods ("java.lang.Runtime");
        retval = true;
      end_try_catch
    case "swing"
      try
        dum = javamethods ("javax.swing.Popup");
        retval = true;
      end_try_catch
    otherwise
      error ("usejava: unrecognized feature '%s'", feature);
  endswitch

endfunction


%!assert (usejava ("desktop"), false)

%% Test input validation
%!error usejava ()
%!error usejava (1, 2)
%!error usejava (1)
%!error <unrecognized feature> usejava ("abc")