--
-- a simple shell for loading plugins and evaluating their functions
-- 

import Plugins
import API

import Data.Either
import Data.Char
import Control.Monad            ( when )
import System.Console.Readline  ( readline )
import System.Exit              ( ExitCode(..), exitWith )


source = "Plugin.hs"
stub   = "Plugin.stub"
object = "Plugin.o"

sym = "resource"

main = do
        makeWith source stub []
        p <- load object ["."] Nothing sym
        shell p

    where
        shell p@(m,v) = do 

                s <- readline "> "
                cmd <- case s of 
                        Nothing     -> exitWith ExitSuccess
                        Just ":quit" -> exitWith ExitSuccess
                        Just s      -> return (chomp s)

                -- possibly recompile if the source changed
                (_,rebuilt,_) <- makeWith source stub []   
                p' <- if rebuilt
                        then return p -- not remade, don't reload
                        else reload m sym >>= \v' -> return (m,v')

                p'' <- eval cmd p'
                shell p''

--
-- shell commands
--
eval "" p = return p

eval ":clear" p = do
        let loop i = when (i < 40) (do putStr "\n" ; loop $! i+1)
        loop 0
        return p

-- apply the user's code
eval cmd@(':':'f':'i':'l':'t':'e':'r':' ':s) (m,v) = 
        putStrLn ((function v) s) >> return (m,v)

eval ":?"  p     = do
        putStrLn$"\":?\"\n"       ++
                 "\":quit\"\n"    ++
                 "\":clear\"\n"   ++
                 "\":filter foo\""
        return p

eval _ p = putStrLn "command not found"  >> return p
--
-- strip trailing whitespace
--
chomp :: String -> String
chomp [] = []
chomp s | isSpace (last s) = chomp $! init s
        | otherwise        = s