module Language.Melody.API (runExpr, runTopLevel, runFile) where
import Text.Parsec
import Language.Melody.Interpret.Types
import Language.Melody.Interpret
import Language.Melody.Parser
import Language.Melody.Syntax
import Control.Monad.Trans.Either

data Error = Parser ParseError | Eval EvalError
           deriving (Show)

type Stack = [Expr Compiled]

type MelodyResult = IO (Either Error Stack)

liftError :: (e -> Error) -> Either e a -> Either Error a
liftError f = either (Left . f) Right

run :: [TopLevel] -> MelodyResult
run = fmap (liftError Eval) . runMelody . mapM_ eval

liftParser :: (String -> Either ParseError a) -> String -> EitherT Error IO a
liftParser p = hoistEither . liftError Parser . p

liftIOParser :: (String -> IO (Either ParseError a)) -> String -> EitherT Error IO a
liftIOParser p = EitherT . fmap (liftError Parser) . p

runExpr, runTopLevel, runFile :: String -> MelodyResult
runExpr s     = runEitherT $ liftParser   parseMelodyExpr s >>= EitherT . run . (:[]) . Exec
runTopLevel t = runEitherT $ liftParser   parseMelody t     >>= EitherT . run . (:[])
runFile f     = runEitherT $ liftIOParser parseSrcFile f    >>= EitherT . run