{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TemplateHaskell #-}
module Main where

import Control.Lens hiding (imap)
import Control.Applicative
import Control.Concurrent
import Control.Monad
import Data.Char
import Data.IORef
import Data.List
import Numeric (showIntAtBase)
import System.IO
--import System.Posix.Signals

import GHC.Stats (getGCStats)

import Control.Monad.Error
import Control.Monad.Reader
import Control.Monad.State
import Control.Monad.Writer

import Data.Map (Map)
import qualified Data.Map as Map

import Buffer
import Process
import Scanner (scan, runScanner, toChar)
import Trammel


data Mode
    = InsertMode
    | NormalMode
    | VerbatimMode
    | SelectRegisterMode
    | DeleteMode
  deriving (Eq)


data VTConfig = VTConfig
    { withOutput :: IO () -> IO ()
    }

data VTState = VTState
    { _buffer :: Buffer
    , _mode :: Mode
    , _processCount :: Int
    , _count :: Maybe Int
    , _register :: Char
    , _registers :: Map Char String
    }

makeLenses ''VTState


defaultRegister :: Char
defaultRegister = '"'

main :: IO ()
main = do
  hSetEcho stdin False
  hSetBuffering stdin NoBuffering

  -- WINCH
  -- TODO installHandler 28 (Catch $ ioctl 0 ...) Nothing

  let st = VTState
          { _mode = InsertMode
          , _buffer = ("!while date; do sleep 1; done", "")
          , _processCount = 0
          , _count = Nothing
          , _register = defaultRegister
          , _registers = Map.empty
          }

  lockRef <- newMVar ()
  qRef <- newIORef st
  let _putState = writeIORef qRef -- TODO atomicModifyIORef (?)
      _getState = readIORef qRef
      _withOutput a = do
          q <- _getState
          withMVar lockRef $ \ _ -> do
              clearLine
              a
              renderInputLine (_count q) (_mode q) (_buffer q)
              hFlush stdout

  let cf = VTConfig
            { withOutput = _withOutput
            }

  -- render initial input line
  _withOutput $ return ()

  uiThread cf _putState _getState


uiThread :: VTConfig -> (VTState -> IO ()) -> IO VTState -> IO ()
uiThread cf putState getState = forever $ do
    q0 <- getState


    _ <- hLookAhead stdin -- wait for input
    --t0 <- getCurrentTime
    -- ((res, s), _) <- runScanner scan
    ((_, s), _) <- runScanner scan
    --t1 <- getCurrentTime
    --putStrLn $ "====> \ESC[32;1m" ++ show s ++ "\ESC[m in " ++
    --            (show $ diffUTCTime t1 t0)
    --            ++ ": \"\ESC[35m" ++ (s >>= colorize . toChar)
    --            ++ "\ESC[m\""
    --case res of
    --    Left msg -> putStrLn $ "  error: " ++ msg
    --    Right _ -> return ()

    -- TODO don't leak C
    let cmd = getCommand (_mode q0) (map toChar s)

    --withOutput cf $ do
    --    putStrLn $ show cmd

    ((eitCmd, lns), q1) <- runVT cf q0 (execCommand cmd)

    -- TODO only putState if it has changed (?)
    putState q1

    withOutput cf $ do
        forM_ lns putStrLn

        whenLeft eitCmd $ \err ->
            ringBell >> putStrLn (prettyError err)

        --when (mode st /= mode st') $ do
        --    putStrLn $ "change mode: " ++ (show $ mode st')



data Command
  = AlertBadInput String
  | InsertString String
  | KillLastWord
  | KillLastChar
  | KillNextChar
  | ExecuteInputBuffer
  | MotionCommand LeftRightMotion
  | MotionCommandWarn LeftRightMotion
  | ChangeMode Mode
  -- TODO Move Count Motion
  --      Delete Count Register Motion
  --      etc.
  | Combine Command Command
  | Nop
  | RingBell
  | AppendCount Int
  | SetCount (Maybe Int)
  | SetRegister Char
  | DeleteEntireLine

instance Monoid Command where
    mempty = Nop
    mappend = Combine



data ExecError
  = UnhandledInputError String
  | OtherError String

instance Error ExecError where
  noMsg = OtherError "something went wrong"


prettyError :: ExecError -> String

prettyError (UnhandledInputError s) =
    pp $ SGR [31] $
        "unhandled input: <" <> SGR [1] (gaudySpecial [35,1] s) <> ">"

prettyError (OtherError s) =
    pp $ SGR [31] $ gaudySpecial [35] s



newtype VT a = VT
    (ReaderT VTConfig
        (ErrorT ExecError
            (WriterT [String]
                (StateT VTState IO
        )))
        a)
  deriving
    ( Applicative
    , Functor
    , Monad
    , MonadError ExecError
    , MonadIO
    , MonadReader VTConfig
    , MonadState VTState
    , MonadWriter [String]
    )

runVT ::
    VTConfig -> VTState -> VT a -> IO ((Either ExecError a, [String]), VTState)

runVT cf st (VT a) =
    runStateT (runWriterT (runErrorT (runReaderT a cf))) st



insertString :: String -> Buffer -> Buffer
insertString s (ls, rs) = (ls ++ s, rs)


execCommand :: Command -> VT ()

execCommand (MotionCommand x) = do
    c <- uses count (maybe 1 id)
    buffer %= move x c

    -- TODO apply mode constraints somewhere else
    whenM (uses mode (==NormalMode) >>&& uses (buffer . _2) null) $
        buffer %= gotoLeft 1

-- TODO Make this "real" warnings, i.e. don't throwError but tell.  This
-- is required in order to perform any Combine-d commands regardless of
-- failed moves.  Currently this is only used to SetCount Nothing (which
-- is defunct atm) Alternatively we could simply reset the state when an
-- error happens Discus!
execCommand (MotionCommandWarn x) = do
    b0 <- use buffer
    execCommand (MotionCommand x)
    b1 <- use buffer

    -- TODO make this a warning or else ...
    when (b0 == b1) $
      throwError (OtherError $ "your motion has no effect: " ++ show x)

execCommand (ChangeMode m) =
    mode .= m

execCommand (InsertString s) =
    buffer %= insertString s

execCommand ExecuteInputBuffer = do

    ---- XXX hack to replace empty command line
    --gets (null . showBuffer . buffer) >>= flip when
    --    (modify $ \q -> q { buffer = ("!","") })

    st <- get

    case showBuffer (_buffer st) of
      ":c" -> do
          let f i = pp $ SGR [38,5,i] $ Plain $ padl 3 '0' $ show i
          tell [ intercalate " " $ map f [0..255]
               ]
      ":r" -> do
          tell [ "--- Registers ---" ]
          tell $ map (\(r, s) -> ['"', r] ++ "  " ++ s) -- TODO pp
               $ Map.toList (_registers st)
      ":s" -> do
          s <- liftIO getGCStats
          tell [ show s ]
      '!' : cmdline -> do
          --tell [ "spawn: " ++ cmdline ]
          -- "input: <" ++ (showBuffer b >>= reform 32) ++ ">" ]
          -- TODO register process
          i <- processCount <<+= 1
          cf <- ask
          liftIO $ forkIO $ spawn i (withOutput cf) cmdline
          return ()
      "" -> do
          liftIO ringBell
      s -> do
          let s' = SGR [32] $ gaudySpecial [1] s
          tell [ pp $ "input: " <> s'
               , pp $ SGR [35] $ gaudySpecial [1] $ pp s'
               ]

    buffer .= emptyBuffer

execCommand KillNextChar = do
    whenM (uses (buffer . _2) null) $
          throwError (OtherError "nothing to kill right")

    buffer . _2 %= tail

execCommand KillLastChar = do
    whenM (uses (buffer . _1) null) $
          throwError (OtherError "nothing to kill left")

    buffer . _1 %= init

execCommand KillLastWord = do
    whenM (uses (buffer . _1) null) $
          throwError (OtherError "nothing to kill left")

    buffer . _1 %= foldr dropWhileEnd `flip` [not . isSpace, isSpace]

execCommand (AlertBadInput s) =
    throwError (UnhandledInputError s)

execCommand (Combine c1 c2) = do
    cf <- ask
    q0 <- get

    ((eSt1, lines1), q1) <- liftIO $ runVT cf q0 (execCommand c1)

    -- TODO "stack trace"
    whenLeft eSt1 throwError

    ((eSt2, lines2), q2) <- liftIO $ runVT cf q1 (execCommand c2)

    -- TODO "stack trace"
    whenLeft eSt2 throwError

    tell lines1
    tell lines2

    put q2

execCommand Nop = return ()

execCommand RingBell = liftIO ringBell

execCommand (AppendCount i) =
    count %= Just . (i+) . maybe 0 (10*)

execCommand (SetCount i) =
    count .= i

execCommand (SetRegister c) =
    register .= c

execCommand DeleteEntireLine =
    -- TODO Numbered registers "0 to "9
    --      Small delete _register "-
    modify $ \q -> do

        let v = Just $ showBuffer $ _buffer q
            r = _register q

        q & buffer .~ emptyBuffer
          & register .~ defaultRegister
          & registers %~ (at r .~ v) .
                         (at defaultRegister .~ v)


-- XXX assumes that the cursor is already at the (cleared) input line
-- TODO renderInputLine looks like it wants to be -> VT ()
renderInputLine :: Maybe Int -> Mode -> Buffer -> IO ()
renderInputLine mb_cnt m (lhs, rhs) = do
    renderRight $
        SGR [30,1] $
        Plain (show m) <>
            maybe Empty
                  (("["<>) . (<>"]") . SGR [33,1] . Plain . show)
                  mb_cnt
    renderLeft $ promptString m <> gaudySpecial [35] (lhs ++ rhs)
    moveCursorLeft $ length $ lit rhs


renderLeft :: Trammel String -> IO ()
renderLeft = putStr . pp


renderRight :: Trammel String -> IO ()
renderRight a = do
    saveCursor
    moveCursorRight 1024 -- XXX obviously, this is a hack..^_^
    moveCursorLeft $ len a - 1
    renderLeft a
    unsaveCursor



promptString :: Mode -> Trammel String
promptString NormalMode = SGR [33,1] "@ "
promptString InsertMode = "> "
promptString SelectRegisterMode = "\" "
promptString DeleteMode = SGR [31,1] "> "
promptString VerbatimMode = SGR [34,1] "^ "


spans :: (a -> Bool) -> [a] -> [Either [a] [a]]
spans p xs = f_r (span p_r xs)
  where
    p_r = not . p
    p_l = p
    f_r (as, bs) = Right as : if null bs then [] else f_l (span p_l bs)
    f_l (as, bs) = Left  as : if null bs then [] else f_r (span p_r bs)


gaudySpans :: [Int] -> (Char -> Bool) -> String -> Trammel String
gaudySpans c p =
    mconcat . map (either (SGR c . Plain . lit) Plain) . spans p


gaudySpecial :: [Int] -> String -> Trammel String
gaudySpecial c = gaudySpans c (not . isPrint)


lit :: String -> String
lit = (>>= f)
  where f '\ESC' = "^["
        f c = showLitChar c ""


clearLine :: IO ()
clearLine =
    putStr "\x1b[2K" >>
    moveCursorLeft 1024


ringBell :: IO ()
ringBell = putStr "\x07" -- BEL '\a'


saveCursor :: IO ()
saveCursor = putStr "\x1b[s"

unsaveCursor :: IO ()
unsaveCursor = putStr "\x1b[u"


moveCursorLeft :: Int -> IO ()
moveCursorLeft 0 = return ()
moveCursorLeft i = putStr $ "\x1b[" ++ show i ++ "D"


moveCursorRight :: Int -> IO ()
moveCursorRight 0 = return ()
moveCursorRight i = putStr $ "\x1b[" ++ show i ++ "C"


-- TODO? charToCode c = "\\x" ++ showHex (ord c)
charToCode :: Char -> String
charToCode c = "\\x" ++ showIntAtBase 16 intToDigit (ord c) ""


dmap :: Keymap
dmap =
  [ ("\x1b", ChangeMode NormalMode)
  , ("d", DeleteEntireLine <> ChangeMode NormalMode)
  ]


selectRegisterMap :: Keymap
selectRegisterMap =
  [ ("\x1b", ChangeMode NormalMode)
  ]
  ++ (map (\c -> ([c], SetRegister c <> ChangeMode NormalMode))
          (['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9'] ++ ".%#:-\""))


nmap :: Keymap
nmap =
  [ ("\x1b", SetCount Nothing)
            -- ^TODO RingBell if count is already Nothing
            --  TODO cancel any unfinished commands
  , ("i", ChangeMode InsertMode <> SetCount Nothing)
  , ("a", ChangeMode InsertMode <> SetCount Nothing <> MotionCommand GotoRight)
  , ("I", ChangeMode InsertMode <> MotionCommand GotoFirstChar)
  , ("A", ChangeMode InsertMode <> MotionCommand GotoEndOfLine)
  , ("|", MotionCommandWarn GotoColumn <> SetCount Nothing)
  , ("$", MotionCommandWarn GotoEndOfLine <> SetCount Nothing)
  , ("h", MotionCommandWarn GotoLeft <> SetCount Nothing)
  , ("l", MotionCommandWarn GotoRight <> SetCount Nothing)
  , ("b", MotionCommandWarn WordsBackward <> SetCount Nothing)
  , ("w", MotionCommandWarn WordsForward <> SetCount Nothing)
  , ("d", ChangeMode DeleteMode)
  , ("\"", ChangeMode SelectRegisterMode <> SetCount Nothing)
  , ("\x1b[C", MotionCommandWarn GotoRight <> SetCount Nothing)
  , ("\x1b[D", MotionCommandWarn GotoLeft <> SetCount Nothing)
  , ("\x0a", ExecuteInputBuffer <> ChangeMode InsertMode <> SetCount Nothing)
  ]
  ++ (map (\i -> (show i, AppendCount i)) [0..9])
  -- XXX
  --  if we would want 0 to move the cursor to the first character of the
  --  line, then we would need ("0", x)
  --    where
  --      x :: Command
  --      x = Embed f
  --      f :: VT Command
  --      f = gets (isJust . count) >>=
  --          return . bool (MotionCommand GotoFirstChar) (AppendCount 0)
  --      bool :: a -> a -> Bool -> a
  --      bool _ a True = a
  --      bool a _ False = a
  --  and also we would have to extend data Command by Embed (VT Command)
  --  execCommand (Embed a) = a >>= execCommand
  --
  --  This all looks quite strange, so just use | if you want that movement...
  --  ^_^


imap :: Keymap
imap =
  [ ("\x1b", ChangeMode NormalMode <> MotionCommand GotoLeft)
  , ("\x01", MotionCommandWarn GotoFirstChar)
  , ("\x05", MotionCommandWarn GotoEndOfLine)
  , ("\x1b[3~", KillNextChar)
  , ("\x1b[C", MotionCommandWarn GotoRight)
  , ("\x1b[D", MotionCommandWarn GotoLeft)
  , ("\x16", ChangeMode VerbatimMode) -- ^V
  , ("\x17", KillLastWord) -- ^W
  , ("\x0a", ExecuteInputBuffer)
  , ("\x7f", KillLastChar) -- Delete
  , ("\x08", KillLastChar) -- BackSpace
  , ("\x1bOc", MotionCommandWarn WordsForward)
  , ("\x1bOd", MotionCommandWarn WordsBackward)
  ]


type Keymap = [(String, Command)]

instance  Show Mode  where
  show NormalMode = "normal"
  show InsertMode = "insert"
  show VerbatimMode = "verbatim"
  show SelectRegisterMode = "select register"
  show DeleteMode = "delete"


getCommand :: Mode -> String -> Command

getCommand InsertMode s = maybe (InsertString s) id $ lookup s imap

getCommand NormalMode s =
    maybe (AlertBadInput s <> SetCount Nothing) id $ lookup s nmap

getCommand VerbatimMode s = InsertString s <> ChangeMode InsertMode

getCommand SelectRegisterMode s =
    maybe (AlertBadInput s) id $ lookup s selectRegisterMap
          -- ^ TODO clear bad input

getCommand DeleteMode s = maybe (AlertBadInput s) id $ lookup s dmap


-- TODO Control.Monad.whenLeft
whenLeft :: Monad m => Either a b -> (a -> m ()) -> m ()
whenLeft (Left x) f = f x
whenLeft _ _ = return ()

whenM :: Monad m => m Bool -> m () -> m ()
whenM a b = a >>= flip when b

infixl 1 >>&&

(>>&&) :: Monad m => m Bool -> m Bool -> m Bool
a >>&& b = do
    ra <- a
    rb <- b
    return $ ra && rb


padl :: Int -> a -> [a] -> [a]
padl n c s
  | length s < n = padl n c (c : s)
  | otherwise = s