{-# LANGUAGE FunctionalDependencies #-}
module DependencyGenerator
  ( DepGenM
  , DepGenM'
  , evalDepGenM
  , inject
  , runFunction
  , runFunctionIO
  , mapDepGenM
  , mapDepGenM_
  , filterDepGenM
  , unzipFstDepGenM
  , unzipSndDepGenM
  , unzipDepGenM

  , joinPaths
  , fileComponents
  , isImageExtension
  , convertedImageFilename
  , applyTemplate
  , listDirectory
  , readTemplate
  , convertImage
  , saveFile
  , makeDir
  , runPandoc
  ) where

import Types.Token (Token(..))
import Types.Values
import Types.Value (Valuable(..))
import Types.Function (Function(..))
import Types.FunctionIO (FunctionIO(..))
import Types.Dependency (Action(..), Dependency, makeDependency)

import Control.Monad.State (MonadState, State, runState, put, get)
import Control.Monad.Writer (MonadWriter, WriterT, execWriterT, tell)

newtype DepGenM a = DepGenM { unDepGenM :: WriterT [Dependency] (State Int) a }
  deriving (Functor, Applicative, Monad, MonadState Int, MonadWriter [Dependency])

type DepGenM' a = DepGenM (Token a)

evalDepGenM' :: Int -> DepGenM () -> ([Dependency], Int)
evalDepGenM' top m = runState (execWriterT (unDepGenM m)) top

evalDepGenM :: DepGenM () -> [Dependency]
evalDepGenM m = fst (evalDepGenM' 0 m)

tellDep :: Dependency -> DepGenM ()
tellDep dep = tell [dep]

genDependencyM :: (Token a -> DepGenM Dependency) -> DepGenM' a
genDependencyM f = do
  top <- get
  let top' = top + 1
      target = Token top'
  put top'
  result <- f target
  tellDep result
  pure target

genDependency :: (Token a -> Dependency) -> DepGenM' a
genDependency f = genDependencyM (pure . f)

inject :: Valuable a => a -> DepGenM' a
inject x = genDependency (makeDependency NoToken (Inject (toValue x)))

getListElem :: Token [a] -> DepGenM' a
getListElem outer = genDependency (makeDependency outer GetListElem)

setListElem :: Token a -> Token [a] -> DepGenM ()
setListElem a outer = do
  tellDep (makeDependency a SetListElem outer)

runFunction :: Function -> Token a -> DepGenM' b
runFunction f input = genDependency (makeDependency input (Function f))

runFunctionIO :: FunctionIO -> Token a -> DepGenM' b
runFunctionIO f input = genDependency (makeDependency input (FunctionIO f))

runFunctionIO' :: FunctionIO -> Token a -> DepGenM ()
runFunctionIO' f input = tellDep $ makeDependency input (FunctionIO f) NoToken

mapDepGenM :: (Token a -> DepGenM' b) -> Token [a] -> DepGenM' [b]
mapDepGenM f input = genDependencyM $ \target -> do
  top <- get
  let (res, top') = evalDepGenM' top $ do
        inp <- getListElem input
        outp <- f inp
        setListElem outp target
  put top'
  pure (makeDependency input (MapComp res) target)

mapDepGenM_ :: (Token a -> DepGenM ()) -> Token [a] -> DepGenM ()
mapDepGenM_ f input = do
  _ <- mapDepGenM (\x -> f x >> pure NoToken) input
  pure ()

filterDepGenM :: Token [Bool] -> Token [a] -> DepGenM' [a]
filterDepGenM mask input = do
  genDependency (makeDependency (TupleToken (input, mask)) FilterComp)

unzipFstDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [a])
unzipFstDepGenM t = do
  t' <- toToken t
  case t' of
    ZipToken (a, _) -> pure a
    Token _ -> genDependency (makeDependency t' UnzipFst)

unzipSndDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [b])
unzipSndDepGenM t = do
  t' <- toToken t
  case t' of
    ZipToken (_, b) -> pure b
    Token _ -> genDependency (makeDependency t' UnzipSnd)

unzipDepGenM :: TokenableTo [(a, b)] t => t -> DepGenM (Token [a], Token [b])
unzipDepGenM t = do
  t' <- toToken t
  a <- unzipFstDepGenM t'
  b <- unzipSndDepGenM t'
  pure (a, b)

class TokenableTo t s | s -> t where
  toToken :: s -> DepGenM' t

instance TokenableTo a (Token a) where
  toToken = pure

instance TokenableTo a (DepGenM' a) where
  toToken = id

joinPaths :: (TokenableTo FilePath a, TokenableTo FilePath b) => (a, b) -> DepGenM' FilePath
joinPaths (a, b) = do
  a' <- toToken a
  b' <- toToken b
  runFunction JoinPaths $ TupleToken (a', b')

fileComponents :: TokenableTo FilePath a => a -> DepGenM' (String, String)
fileComponents a = runFunction FileComponents =<< toToken a

isImageExtension :: TokenableTo FilePath a => a -> DepGenM' Bool
isImageExtension a = runFunction IsImageExtension =<< toToken a

convertedImageFilename :: TokenableTo FilePath a => a -> DepGenM' FilePath
convertedImageFilename a = runFunction ConvertedImageFilename =<< toToken a

applyTemplate :: (TokenableTo Template a, TokenableTo String b) => (a, b) -> DepGenM' String
applyTemplate (a, b) = do
  a' <- toToken a
  b' <- toToken b
  runFunction ApplyTemplate $ TupleToken (a', b')

listDirectory :: TokenableTo FilePath a => a -> DepGenM' [FilePath]
listDirectory a = runFunctionIO ListDirectory =<< toToken a

readTemplate :: TokenableTo FilePath a => a -> DepGenM' Template
readTemplate a = runFunctionIO ReadTemplate =<< toToken a

convertImage :: (TokenableTo (FilePath, FilePath) a, TokenableTo ImageConversionSettings b) => (a, b) -> DepGenM ()
convertImage (a, b) = do
  a' <- toToken a
  b' <- toToken b
  runFunctionIO' ConvertImage $ TupleToken (a', b')

saveFile :: (TokenableTo String a, TokenableTo FilePath b) => (a, b) -> DepGenM ()
saveFile (a, b) = do
  a' <- toToken a
  b' <- toToken b
  runFunctionIO' SaveFile $ TupleToken (a', b')

makeDir :: TokenableTo FilePath a => a -> DepGenM ()
makeDir a = runFunctionIO' MakeDir =<< toToken a

runPandoc :: TokenableTo FilePath a => a -> DepGenM' String
runPandoc a = runFunctionIO RunPandoc =<< toToken a