--------------------------------------------------------------------------------
--  $Id: RepMonad.hs,v 1.1 2004/03/26 12:18:05 graham Exp $
--
--  Copyright (c) 2004, G. KLYNE.  All rights reserved.
--  See end of this file for licence information.
--------------------------------------------------------------------------------
-- |
--  Module      :  RepMonad
--  Copyright   :  (c) 2004, Graham Klyne
--  License     :  GPL V2
--
--  Maintainer  :  Graham Klyne
--  Stability   :  provisional
--  Portability :  H98
--
--  RepMonad:  Composed state and IO monad for RepToRDF
--
--------------------------------------------------------------------------------

module RepMonad
    ( RepStateIO, RepState(..)
    , setFormat, setGraph
    , setInfo, resetInfo, setError, resetError, setExitcode
    , emptyState
    , RepFormat(..)
    , repError
    , reportLines, reportLine
    )
where

import RDFGraph
    ( RDFGraph, emptyRDFGraph )

import Control.Monad.Trans
    ( MonadTrans(..) )

import Control.Monad.State
    ( MonadState(..), modify, StateT(..), execStateT )

import System
    ( ExitCode(ExitSuccess,ExitFailure) )

import IO
    ( hPutStrLn, stderr )

------------------------------------------------------------
--  State and state monad for RepToRDF program
------------------------------------------------------------
--
--  Uses StateT Monad transformer:
--  See example by Mark Carroll at http://www.haskell.org/hawiki/MonadState

data RepFormat = N3 | NT | RDF
    deriving (Eq, Show)

data RepState = RepState
    { format    :: RepFormat
    , graph     :: RDFGraph         -- current graph
    , infomsg   :: Maybe String     -- information message, or Nothing
    , errormsg  :: Maybe String     -- error message, or Nothing
    , exitcode  :: ExitCode
    }

type RepStateIO a = StateT RepState IO a

emptyState = RepState
    { format    = N3
    , graph     = emptyRDFGraph
    , infomsg   = Nothing
    , errormsg  = Nothing
    , exitcode  = ExitSuccess
    }

setFormat :: RepFormat -> RepState -> RepState
setFormat   fm state = state { format = fm }

setGraph :: RDFGraph -> RepState -> RepState
setGraph    gr state = state { graph = gr }

setInfo :: String -> RepState -> RepState
setInfo msg state = state { infomsg = Just msg }

resetInfo :: RepState -> RepState
resetInfo state = state { infomsg = Nothing }

setError :: String -> RepState -> RepState
setError msg state = state { errormsg = Just msg }

resetError :: RepState -> RepState
resetError state = state { errormsg = Nothing }

setExitcode :: ExitCode -> RepState -> RepState
setExitcode ec state = state { exitcode = ec }

------------------------------------------------------------
--  Report error and set exit status code
------------------------------------------------------------

repError :: String -> Int -> RepStateIO ()
repError msg sts =
    do  { reportLine $ msg
        ; if sts == 4 then
            reportLine $ "Use 'RepToRDF -?' for help"
          else
            return ()
        ; modify $ setExitcode (ExitFailure sts)
        }

------------------------------------------------------------
--  Output text to the standard error stream
------------------------------------------------------------
--
--  Each string in the supplied list is a line of text to
--  be displayed.

reportLines  :: [String] -> RepStateIO ()
reportLines text =
    sequence_ (map reportLine text)

reportLine  :: String -> RepStateIO ()
reportLine line =
    -- lift putStrLn line
    lift $ hPutStrLn stderr line

--------------------------------------------------------------------------------
--
--  Copyright (c) 2004, G. KLYNE.  All rights reserved.
--
--  This 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 software 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 RepToRDF; if not, write to:
--    The Free Software Foundation, Inc.,
--    59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
--  or view the web page at:
--    http://www.gnu.org/copyleft/gpl.html
--
--------------------------------------------------------------------------------
-- $Source: /file/cvsdev/CompileRDF/RepMonad.hs,v $
-- $Author: graham $
-- $Revision: 1.1 $
-- $Log: RepMonad.hs,v $
-- Revision 1.1  2004/03/26 12:18:05  graham
-- Created report description compiler
--