{-# LANGUAGE CPP #-}
{-------------------------------------------------------------------------------

        Copyright:              Bernie Pope 2004

        Module:                 CmdLine

        Description:            The Baskell interpreter command line.

        Primary Authors:        Bernie Pope

        Notes:

        Will use GNU readline if it is available.

-------------------------------------------------------------------------------}

{-
    This file is part of baskell.

    baskell 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.

    baskell 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 baskell; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

module CmdLine
   (Command (..)
   , getCommand
   , initializeCmdLine
  )
   where

import Parser  (expParser)

import AST  (Exp)

import Data.Char(isSpace)

import Text.ParserCombinators.Parsec
   (ParseError
   , runParser
   , (<|>)
   , eof
  )

import ParserUtils
   (Parser
   , word
   , singleQuoted
   , colon
  )

#ifdef READLINE
import qualified System.Console.Readline as Readline
   (readline
   , addHistory
   , initialize
  )
#endif

import Lexer
   (lexer)

--------------------------------------------------------------------------------

data Command
   = Load FilePath
   | Quit
   | Browse
   | Eval Exp
   | Type Exp
   | Help
#ifdef DEBUG
   | ShowAST
   | ShowDepend
#endif

-- read some input from the user
-- parse the input and return the corresponding command
getCommand :: IO Command
getCommand
   = do input <- readline "baskell> "
        case input of
           Nothing -> return Quit
           Just line
              -> if all isSpace line
                    then getCommand
                    else do addHistory line
                            case parseCommandLine line of
                               Left e -> do putStrLn $ "Parse error: " ++ show e
                                            putStrLn $ ":h for help, :q to quit"
                                            getCommand
                               Right cmd -> return cmd

parseCommandLine :: String -> Either ParseError Command
parseCommandLine input
   = runParser commandLineParser () src (lexer src input)
   where
   src = "baskell command line"

-- a command line is either a colon-prefixed command
-- or an expression to evaluate
commandLineParser :: Parser Command
commandLineParser
   = do cmd <- colonCommand <|> evalCommand
        eof
        return cmd

colonCommand :: Parser Command
colonCommand
   = do colon
        cmd <- word
        case cmd of
           "q" -> return Quit
           "h" -> return Help
           "b" -> return Browse
           "l" -> do fileName <- singleQuoted
                     return $ Load fileName
           "t" -> do exp <- expParser
                     return $ Type exp
#ifdef DEBUG
           "ast"    -> return ShowAST
           "depend" -> return ShowDepend
#endif
           other -> fail $ "unknown command: " ++ show cmd

evalCommand :: Parser Command
evalCommand
   = do exp <- expParser
        return $ Eval exp

--------------------------------------------------------------------------------

-- optional support for GNU Readline

initializeCmdLine :: IO ()
initializeCmdLine
#ifdef READLINE
   = Readline.initialize
#else
   = return ()
#endif

readline :: String -> IO (Maybe String)
readline prompt
#ifdef READLINE
   = Readline.readline prompt
#else
   = do putStr prompt
        input <- getLine
        return $ Just input
#endif

addHistory :: String -> IO ()
addHistory str
#ifdef READLINE
   = Readline.addHistory str
#else
   = return ()
#endif