Definitions.hs

module Language.Haskell.Format.Definitions (HaskellSource(..), Reformatted(..), Formatter(..), Suggestion(..)) where

import Control.Applicative
import Control.Monad
import Data.Monoid

type ErrorString = String

newtype HaskellSource = HaskellSource String
  deriving Eq

newtype Suggestion = Suggestion String

instance Show Suggestion where
  show (Suggestion text) = text

data Reformatted = Reformatted { reformattedSource :: HaskellSource, suggestions :: [Suggestion] }

instance Monoid Reformatted where
  mempty = Reformatted undefined []
  (Reformatted _ suggestionsA) `mappend` (Reformatted sourceB suggestionsB) = Reformatted sourceB
                                                                                (suggestionsA <> suggestionsB)

data Formatter = Formatter { unFormatter :: HaskellSource -> Either ErrorString Reformatted }

instance Monoid Formatter where
  mempty = Formatter (\source -> Right (Reformatted source []))
  (Formatter f) `mappend` (Formatter g) = Formatter (asReformatter g <=< f)

asReformatter :: (HaskellSource -> Either ErrorString Reformatted) -> Reformatted -> Either ErrorString Reformatted
asReformatter formatter r = (r <>) <$> formatter (reformattedSource r)