--******************************************************************************
--*                                                                            *
--*  File:        LibrarySupport.lua                    Revision:  1.0         *
--*                                                                            *
--*  Purpose:     provides a simple "library search and import" mechanism      *
--*                                                                            *
--*  Creation:    13.03.2002                   Last Modification:  13.03.2002  *
--*                                                                            *
--*  Platform:    IBM-compatible PC running Windows 98SE                       *
--*                                                                            *
--*  Environment: Lua 4.0, TkLua 4.0                                           *
--*                                                                            *
--*  Author:      Andreas Rozek           Phone:  ++49 (711) 6770682           *
--*               Kirschblütenweg 15      Fax:    -                            *
--*             D-70569 Stuttgart         EMail:  Andreas.Rozek@T-Online.De    *
--*               Germany                                                      *
--*                                                                            *
--*  URL:         http://www.Andreas-Rozek.de/                                 *
--*                                                                            *
--*  Copyright:   the software is published under the "GNU Lesser General Pub- *
--*               lic  License" (see "http://www.fsf.org/copyleft/lesser.html" *
--*               for additional information)                                  *
--*                                                                            *
--*  Comments:    this file should be copied into a directory  where it can be *
--*               found (by 'dofile') without the search mechanism implemented *
--*               below                                                        *
--*                                                                            *
--*  Known Bugs:  absolute path names (of library files) are not yet handled   *
--*                                                                            *
--******************************************************************************

--**** do not execute this script more often than once ****

  if (type(import) == "function") then return nil; end;

--**** retrieve some platform-specific settings for library imports ****

  LuaHome    = getenv("LuaHome") or ".";          -- retrieve Lua home directory
  LuaLibList = getenv("LuaLibList") or ".";      -- retrieve library folder list

  if (tkeval ~= nil) then             -- use Tk to determine the actual platform
    local Platform = tkeval("set tcl_platform(platform)")[1];
    if     (Platform == "windows") then
      LuaPathSeparator,LuaListSeparator = "\\",";";
    elseif (Platform == "macintosh") then
      LuaPathSeparator,LuaListSeparator = ":",";";
    else --(Platform == "unix") then
      LuaPathSeparator,LuaListSeparator = "/",";";
    end;
  else                             -- read or "guess" platform-specific settings
    LuaPathSeparator = getenv("LuaPathSeparator");
      if (LuaPathSeparator == nil) and (strfind(LuaHome..LuaLibList,"\\",1,1) ~= nil) then
        LuaPathSeparator = "\\";
      end;

      LuaHome = gsub(gsub(LuaHome, "^ *",""), " *$","");    -- "trims" 'LuaHome'
      if (LuaPathSeparator == nil) and (strfind(LuaHome,":",3,1) ~= nil) then
        LuaPathSeparator = ":";
      end;

      if (LuaPathSeparator == nil) and (strfind(LuaHome..LuaLibList,"/",1,1) ~= nil) then
        LuaPathSeparator = "/";
      end;
    assert(strfind("\\:/",LuaPathSeparator,1,1),"invalid path separator \""..LuaPathSeparator.."\"");

    LuaListSeparator = getenv("LuaListSeparator") or ";";
    assert(LuaListSeparator == ";", "invalid search list separator \""..LuaListSeparator.."\"");
  end;

  local LibList = {};
  gsub(LuaLibList..LuaListSeparator, "([^"..LuaListSeparator.."]*)"..LuaListSeparator, -- tricky!
    function (Capture)
      Capture = gsub(gsub(Capture, "^ *",""), " *$","");    -- "trims" 'Capture'
      if (Capture == "") then return ""; end;        -- "" is required by parser

      if (strsub(Capture,-1) ~= LuaPathSeparator) then
        Capture = Capture..LuaPathSeparator;
      end;

      tinsert(%LibList,Capture);
    end
  );

--******************************************************************************
--*                                                                            *
--* import     looks for the given files in a directory list and executes them *
--*                                                                            *
--******************************************************************************

  function import (FileName, ...)
    local ArgCount = getn(arg);
    if (ArgCount > 0) then
      import(FileName);
      for i = 1,getn(arg) do
        import(arg[i]);
      end;
    end;

    FileName = gsub(gsub(FileName, "^ *",""), " *$","");   -- "trims" 'FileName'
    assert(FileName ~= "", "empty \"FileName\" given");

    if (LuaPathSeparator ~= "/") then   -- '/' is the "cross-platform" path sep.
      FileName = gsub(FileName, "/", LuaPathSeparator);
    end;

    for i = 1,getn(%LibList) do
      local FileHandle,ErrMsg = openfile(%LibList[i]..FileName,"r");
      if (FileHandle == nil) and (strlower(strsub(FileName,-4)) ~= ".lua") then
        FileHandle,ErrMsg = openfile(%LibList[i]..FileName..".lua","r");
        if (FileHandle ~= nil) then
          FileName = FileName..".lua";
        end;
      end;

      if (FileHandle ~= nil) then
        closefile(FileHandle);
        dofile(%LibList[i]..FileName);
        return nil;                  -- 'nil' seems to be required by the parser
      end;
    end;

    error("Library file \""..FileName.."\" could not be found");
  end;