Filesystem.hs

{-# LANGUAGE MultiParamTypeClasses, FlexibleContexts, ExistentialQuantification, ScopedTypeVariables #-}
{-
  This module is part of Chatty.
  Copyleft (c) 2014 Marvin Cohrs

  All wrongs reversed. Sharing is an act of love, not crime.
  Please share Antisplice with everyone you like.

  Chatty is free software: you can redistribute it and/or modify
  it under the terms of the GNU Affero General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Chatty is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  GNU Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License
  along with Chatty. If not, see <http://www.gnu.org/licenses/>.
-}

module System.Chatty.Filesystem where

import Control.Arrow
import Control.Monad
import Control.Monad.State
import Control.Monad.Identity
import Data.Chatty.Atoms
import Data.List
import Data.Monoid
import qualified Data.Text.IO as T
import Text.Chatty.Printer
import Text.Chatty.Scanner

data FSExec a = FSSucc a
              | NoPermission
              | NotFound

data File m = File {
    loadFun :: m (FSExec ()),
    saveFun :: m (FSExec ()),
    leftBehind :: String,
    rightPending :: String
  }
newtype Path = MultiPath [PathSpec] deriving (Eq,Ord,Show)
data PathSpec = Path PathRoot [PathSeg] deriving (Eq,Ord,Show)
data PathRoot = Absolute | Relative deriving (Eq,Ord,Show)
data PathSeg = SelParent | SelChild String deriving (Eq,Ord,Show)
type FileA m = Atom (File m)

data Mountpoint m = forall a. Mount {
  subMounts :: [Mountpoint m],
  mstate :: Atom a,
  mpath :: Path,
  mopen :: Path -> (Atom a, Path) -> m (FSExec (FileA m))
  }

class Monad m => ChFilesystem m where
  fopen :: Path -> m (FSExec (FileA m))
  fpwd :: m Path
  fcd :: Path -> m ()

class Monad m => CanLoad m n where
  fload :: FileA n -> m (FSExec ())

class Monad m => CanSave m n where
  fsave :: FileA n -> m (FSExec ())

class Monad m => CanMount m n where
  fmount :: Mountpoint n -> m ()

data FilePrinterT m a = FilePrinter { runFilePrinterT :: FileA m -> m a }
data FileScannerT m a = FileScanner { runFileScannerT :: FileA m -> m a }

instance Monad m => Monad (FilePrinterT m) where
  return a = FilePrinter $ \_ -> return a
  m >>= f = FilePrinter $ \d -> do a <- runFilePrinterT m d; runFilePrinterT (f a) d

instance Monad m => Monad (FileScannerT m) where
  return a = FileScanner $ \_ -> return a
  m >>= f = FileScanner $ \d -> do a <- runFileScannerT m d; runFileScannerT (f a) d

instance Functor f => Functor (FilePrinterT f) where
  fmap f a = FilePrinter $ fmap f . runFilePrinterT a

instance Functor f => Functor (FileScannerT f) where
  fmap f a = FileScanner $ fmap f . runFileScannerT a

instance MonadTrans FilePrinterT where
  lift m = FilePrinter $ \_ -> m

instance MonadTrans FileScannerT where
  lift m = FileScanner $ \_ -> m

instance MonadIO m => MonadIO (FilePrinterT m) where
  liftIO = lift . liftIO

instance MonadIO m => MonadIO (FileScannerT m) where
  liftIO = lift . liftIO

instance ChAtoms m => ChPrinter (FilePrinterT m) where
  mprint s = FilePrinter $ \d -> do
    f <- getAtom d
    putAtom d f{leftBehind=reverse (take (length s) $ rightPending f) ++ leftBehind f, rightPending=drop (length s) $ rightPending f}

instance ChAtoms m => ChScanner (FileScannerT m) where
  mscan1 = FileScanner $ \d -> do
    f <- getAtom d
    putAtom d f{leftBehind=head (rightPending f) : leftBehind f, rightPending=tail $ rightPending f}
    return $ head $ rightPending f
  mscanL = FileScanner $ liftM rightPending . getAtom
  mscannable = FileScanner $ liftM (not . null . rightPending) . getAtom
  mready = mscannable

newtype NullFsT m a = NullFs { runNullFsT :: Path -> [Mountpoint (NullFsT m)] -> m (a, Path, [Mountpoint (NullFsT m)]) }

instance Monad m => Monad (NullFsT m) where
  return a = NullFs $ \p ms -> return (a,p,ms)
  m >>= f = NullFs $ \p ms -> do (a,p',ms') <- runNullFsT m p ms; runNullFsT (f a) p' ms'

instance Functor f => Functor (NullFsT f) where
  fmap f a = NullFs $ \p ms -> fmap (\(a,p,ms) -> (f a,p,ms)) $ runNullFsT a p ms
  
instance MonadTrans NullFsT where
  lift m = NullFs $ \p ms -> do a <- m; return (a,p,ms)

instance MonadIO m => MonadIO (NullFsT m) where
  liftIO = lift . liftIO

instance Monad m => ChFilesystem (NullFsT m) where
  fpwd = NullFs $ \p ms -> return (p,p,ms)
  fopen p = do
    ap <- absPath p
    p' <- NullFs $ \wd ms -> do
      case filter (isPath . snd) $ map (\m -> (m,ap `cmpPath` mpath m)) ms of
        [] -> return (NotFound, wd, ms)
        (p:_) -> return (FSSucc p, wd, ms)
    case p' of
      FSSucc (Mount subs st pa op, p') -> op p' (st,pa)
      NotFound -> return NotFound
  fcd p = NullFs $ \_ ms -> return ((),p,ms)

instance Monad m => CanMount (NullFsT m) (NullFsT m) where
  fmount m = NullFs $ \p ms -> return ((),p,m:ms)

absPath :: ChFilesystem m => Path -> m Path
absPath (MultiPath ps) =
  liftM (MultiPath . concat) $
  forM ps $ \(Path r ps) -> case r of
    Absolute -> return [Path Absolute $ rempar ps]
    Relative -> do
      MultiPath wds <- fpwd
      return $ do
        Path Absolute wd <- wds
        return $ Path Absolute $ rempar (wd++ps)
  where
    rempar (SelChild _:SelParent:rem) = rempar rem
    rempar (a:rem) = a : rempar rem
    rempar [] = []

cmpPath' :: [PathSeg] -> [PathSeg] -> Maybe [PathSeg]
cmpPath' ps [] = Just ps
cmpPath' (SelChild a:as) (SelChild b:bs) | a == b = cmpPath' as bs
cmpPath' (SelParent:as) (SelParent:bs) = cmpPath' as bs
cmpPath' _ _ = Nothing

cmpPath :: Path -> Path -> Path
cmpPath (MultiPath as) (MultiPath bs) = MultiPath $ do
  Path Absolute a <- as
  Path Absolute b <- bs
  case a `cmpPath'` b of
    Nothing -> []
    Just p -> [Path Absolute p]

isPath :: Path -> Bool
isPath (MultiPath p) = not $ null p

path :: String -> Path
path [] = MultiPath []
path ps =
  let took s = takeWhile (/='/') s
      left s = case drop (length $ took s) s of
        [] -> []
        (_:cs) -> cs
      subparse [] = []
      subparse s = case (took s, left s) of
        ([], []) -> []
        ([], l) -> subparse l
        ("..", l) -> SelParent : subparse l
        (".", l) -> subparse l
        (t, l) -> SelChild t : subparse l
  in case head ps of
    '/' -> MultiPath [Path Absolute $ subparse $ tail ps]
    _ -> MultiPath [Path Relative $ subparse ps]

expandofs :: (ChAtoms m,ChFilesystem m) => m (Mountpoint m)
expandofs = do
  a <- newAtom
  putAtom a []
  return $ Mount [] a (MultiPath []) $ \(MultiPath p) (sta,pa) -> do
    fa <- newAtom
    let ld = do
               st <- getAtom sta
               case filter (\(MultiPath x,_) -> not $ null $ intersect x p) st of
                 [] -> putAtom fa (File ld sv "" "") >> return (FSSucc ())
                 (_,tx):_ -> putAtom fa (File ld sv "" tx) >> return (FSSucc ())
        sv = do
               st <- getAtom sta
               fi <- getAtom fa
               case filter (\(_,(MultiPath x,_)) -> not $ null $ intersect x p) $ zip [1..] st of
                 [] -> do
                   putAtom sta ((MultiPath p,reverse (leftBehind fi)++rightPending fi) : st)
                   return (FSSucc ())
                 (i,_):_ -> do
                   putAtom sta (take i st ++ [(MultiPath p,reverse (leftBehind fi)++rightPending fi)] ++ drop (i+1) st)
                   return (FSSucc ())
    putAtom fa $ File ld sv "" ""
    return $ FSSucc fa

printerfs :: (ChPrinter m,ChAtoms m,ChFilesystem m) => m (Mountpoint m)
printerfs = do
  a <- newAtom
  putAtom a ()
  return $ Mount [] a (MultiPath []) $ \p _ -> do
    fa <- newAtom
    let ld = return $ FSSucc ()
        sv = do
          fi <- getAtom fa
          mprint (reverse (leftBehind fi) ++ rightPending fi)
          return $ FSSucc ()
    putAtom fa $ File ld sv "" ""
    return $ FSSucc fa

mount :: (CanMount m m, ChAtoms m, ChFilesystem m) => m (Mountpoint m) -> Path -> m ()
mount mpf p = do
  mp <- mpf
  fmount mp{mpath=p}

withNullFs :: ChAtoms m => NullFsT m a -> m a
withNullFs m = do
  (a,_,_) <- runNullFsT m (path "/") []
  return a

withExpandoFs :: (ChAtoms m, ChAtoms (NullFsT m)) => NullFsT m a -> m a
withExpandoFs m = withNullFs $ do
  mount expandofs (path "/")
  m