> module Imports where

> import Control.Applicative
> import System.IO.Error
> import System.FilePath
> import Data.Foldable
> import Data.Monoid

> import HaLay
> import Parsley

> tryReadFile :: FilePath -> IO String
> tryReadFile s = catch (readFile s) $ \ e ->
>  if isDoesNotExistError e then return "" else ioError e

> pImport :: P Tok [String]
> pImport = teq (KW "import") *> spc *> pSep (teq (Sym ".")) uid <* pRest

> grokImports :: [Tok] -> [[FilePath]]
> grokImports cs = foldMap pure $ parse pImport cs

> getHers :: [String] -> IO [[Tok]]
> getHers p = ready <$>  tryReadFile (joinPath p <.> "hers")

> storySoFar :: [[Tok]] -> IO [[Tok]]
> storySoFar hs = foldMap getHers (hs >>= grokImports)

> instance Monoid x => Monoid (IO x) where
>   mempty = pure mempty
>   mappend x y = mappend <$> x <*> y