## Copyright (C) 2005 Bill Denney
##
## 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
##
## Based on code Copyright (C) 2000 Etienne Grossmann 

## -*- texinfo -*-
## @deftypefn {Function File} {} addpath(dir1, ...)
## Prepends @code{dir1}, @code{...} to the current @code{LOADPATH}.
## If the directory is already in the path, it will place it where you
## specify in the path (defaulting to prepending it).
## 
## @example
## addpath(dir1,'-end',dir2,'-begin',dir3,'-END',dir4,'-BEGIN',dir5)
## @result{} Prepends dir1, dir3 and dir5 and appends dir2 and dir4. 
## @end example
##
## An error will be returned if the string is not a directory, the
## directory doesn't exist or you don't have read access to it.
##
## BUG: This function can't add directories called @code{-end} or
## @code{-begin} (case insensitively).
## @end deftypefn

## Author:        Etienne Grossmann <etienne@cs.uky.edu>
## Modified-By:   Bill Denney <bill@givebillmoney.com>
## Last modified: June 2005

##PKGADD: mark_as_command('addpath')

function ret = addpath(varargin)

  if nargout > 0
    path = varargin{1};
    varargin = varargin(2:end);
  else
    path = LOADPATH;
  end

  dir = '';
  if length(varargin) > 0
    append = 0;
    switch varargin{end}
    case { 0, '0', '-begin', '-BEGIN' }
      varargin = varargin(1:end-1);
    case { 1, '1', '-end', '-END' }
      varargin = varargin(1:end-1);
      append = 1;
    end

    ## Avoid duplicates by stripping pre-existing entries
    path = rmpath(path, varargin{:});

    ## Check if the directories are valid
    for arg = 1:length(varargin)
      p = varargin{arg};
      if nargout == 0 && !isempty(p)
        [s,err,m] = stat(p);
        if (err ~= 0)
	  warning("addpath %s : %s\n",p,m);
	  continue;
        elseif (index(s.modestr,"d") != 1)
	  warning("addpath %s : not a directory (mode=%s)\n",p, s.modestr);
	  continue;
        elseif !((s.modestr(8) == 'r') || ...
	       ((getgid == s.gid) && (s.modestr(5) == 'r')) || ...
	       ((getuid == s.uid) && (s.modestr(2) == 'r')))
	  warning("addpath %s : not readable (mode=%s)\n", p,s.modestr);
	  continue;
        end
      end
      dir = sprintf("%s:%s",dir,p);
    end
      
    ## Add the directories to the current path
    if !isempty(dir)
      dir = dir(2:end);
      if isempty(path) && !isempty(dir)
        path = dir;
      else
        if strcmp(path,':'), path = ''; end
        if append
          path = sprintf("%s:%s", path, dir);
        else
          path = sprintf("%s:%s", dir, path);
        end
      end
    end
  end

  if nargout 
    ret = path; 
  else
    LOADPATH = path; 
  end

%!assert(addpath('','hello'),'hello');
%!assert(addpath('','hello','world'),'hello:world')
%!assert(addpath(':','hello'),'hello:');
%!assert(addpath(':','hello','-end'),':hello');
%!assert(addpath('hello','hello'),'hello');
%!assert(addpath('hello','world'),'world:hello')
%!assert(addpath('hello','world','-end'),'hello:world')
%!assert(addpath('hello:','world','-end'),'hello::world')
%!assert(addpath('hello:','hello','world','-end'),':hello:world')

%!assert(addpath('',''),':')
%!assert(addpath(':',''),':')
%!assert(addpath('hello',''),':hello')
%!assert(addpath('hello:world',''),':hello:world')
%!assert(addpath('hello:world:',''),':hello:world')
%!assert(addpath('hello::world',''),':hello:world')