username = os.getenv("USER") or "<user>"


luaVersion = function(name)
  s = string.format("This is %s.\n", _VERSION)
  s = s .. string.format("It was invoked by %s.\n\n", name)
  io.write(s)
end


haskellVersion = function()
  io.write( "Invoking the Haskell function from Lua...\n" )
  io.write( hsVersion(_VERSION) )
  io.write( "\n\n" )
end

return "Lua: finished loading"

import qualified Scripting.Lua as Lua
import System.Info
import Data.Version

luaScript = "test.lua"

version :: String -> IO String
version name =
  return $
  "This is " ++
  compilerName ++
  " " ++
  (showVersion compilerVersion) ++
  "\nIt was invoked by " ++
  name


main =
  -- Create a new Lua state and open the standard libraries.
  Lua.newstate >>= \ l ->
  Lua.openlibs l >>

  -- Load the test script.
  Lua.loadfile l luaScript >>

  -- Register the 'version' function as 'hsVersion' so that it can be called
  -- from within Lua.
  Lua.registerhsfunction l "hsVersion" version >>

  -- Run the script and get error code.
  Lua.pcall l 0 Lua.multret 0 >>= \ errorCode ->
  if errorCode > 0
    -- A non-zero error code indicates an error. There should be an error
    -- message on the stack. Check if there is and print it if so.
    then
      Lua.isstring l (-1) >>= \ isStr ->
      if isStr
        -- If it is a string, print it along with the error code.
        then
          Lua.tostring l (-1) >>= \ msg ->
          Lua.close l >>
          putStrLn ("error: " ++ msg ++ "(" ++ (show errorCode) ++ ")")
        -- Otherwise print "unknown" along with the error code.
        else
          Lua.close l >>
          putStrLn ("error: unknown (" ++ (show errorCode) ++ ")")

    -- If the pcall was successful, the stack should contain the return value.
    else
      Lua.tostring l (-1) >>= \ rval ->
      putStrLn (luaScript ++ " returned \"" ++ rval ++ "\"\n") >>

      -- Now let's invoke the "luaVersion" function in the script.
      -- We need to invoke it with an argument, so we push it onto the stack.
      Lua.getglobal l "luaVersion" >>
      Lua.pushstring l compilerName >>
      Lua.pcall l 1 0 0 >>
      Lua.pop l 1 >>


      -- Now the "haskellVersion" function in the script, which wraps the
      -- "version" function above.
      Lua.getglobal l "haskellVersion" >>
      Lua.pcall l 0 0 0 >>


      Lua.close l >>

      -- Print something at the very end to make sure that the script hasn't
      -- aborted.
      putStrLn "done"