husky-0.3: src/husky.hs

{-----------------------------------------------------------------
 
  (c) 2008-2009 Markus Dittrich 
 
  This program is free software; you can redistribute it 
  and/or modify it under the terms of the GNU General Public 
  License Version 3 as published by the Free Software Foundation. 
 
  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 Version 3 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.

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

-- | main archy driver
module Main where


-- imports
import System.Console.Readline

-- local imports
import Parser
import CalculatorState
import HelpParser
import InfoRoutines
import Messages
import Prelude
import PrettyPrint
import TokenParser


-- | main
main :: IO ()
main = do
  show_greeting
  parse_it defaultCalcState


-- | main parse function
parse_it :: CalcState -> IO ()
parse_it state = do

  -- prompt and get a line from stdin
  input <- readline $ color_string Red "husky> "
  case input of 
    Nothing   -> parse_it state
    Just ""    -> parse_it state        -- continue without parsing
    Just "\\q" -> return ()             -- quit
    Just "\\v" -> list_variables state  -- list all defined variables
                  >> parse_it state
    Just "\\t" -> show_time             -- show current time
                  >> parse_it state
    Just line -> do                     -- otherwise calculate 

      addHistory line

      -- parse it as a potential help request
      -- if it succeeds we parse the next command line, otherwise
      -- we channel it into the calculator parser
      case runParser help state "" line of
        Right helpMsg  -> putStr helpMsg 
                          >> parse_it state   
        Left _         ->

          -- parse it as a calculation or unit conversion
          case runParser main_parser state "" line of

            Left er  -> print_error_message (show er) 
                        >> parse_it state

            -- if the parser succeeds we still check for special
            -- error conditions in our parse state that may have
            -- been triggered by errors outside the parser (e.g.,
            -- unit conversion may have failed for lack of proper
            -- conversion function etc.)
            Right ((result,unit), newState) -> 
              case have_special_error newState of
                Just err -> (putStr $ "Error: " ++ err)
                Nothing  -> husky_result $ (show result):[unit]

              >> let cleanState = reset_state newState in
                 parse_it cleanState