{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Main where

import Control.Applicative
import Control.Concurrent
import Control.Concurrent.MVar
import Control.Monad
import Data.Char
import Data.IORef
import Data.List
import Data.Time.Clock (getCurrentTime)
import Data.Time.Format (formatTime)
import Numeric (showIntAtBase)
import System.IO
import System.Locale (defaultTimeLocale, rfc822DateFormat)
--import System.Posix.Signals

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

import Buffer

data VTConfig = VTConfig
    {
    }

data VTState = VTState
    { buffer :: Buffer
    , mode :: Mode
    }

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

  tid <- myThreadId

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

  let st = VTState
          { mode = InsertMode
          , buffer = ("Was geht ab, Junge?", " ^_^")
          }

  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 (mode q) (buffer q)
              hFlush stdout

  -- render initial input line
  withOutput $ return ()

  forkIO $ dateThread withOutput 1000000

  uiThread withOutput putState getState


dateThread :: (IO () -> IO ()) -> Int -> IO ()
dateThread withOutput delay = forever $ do
    t <- liftIO getCurrentTime
    withOutput $
      putStrLn $ formatTime defaultTimeLocale rfc822DateFormat t
    threadDelay delay


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

    ((eitCmd, lines), q1) <- runVT VTConfig q0 $ do
        c <- getCommand (mode q0)
        execCommand c
        return c

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

    let mbErr = case eitCmd of
                  Left err -> Just err
                  Right c ->
                      -- TODO move this to execCommand / throwError
                      case c of
                        MotionCommand motion | buffer q0 == buffer q1 ->
                            Just (OtherError $ "motion failed: " ++ show motion)
                        _ ->
                            Nothing

    withOutput $ do
        forM_ lines putStrLn

        case mbErr of
          Just err -> ringBell >> putStrLn (prettyError err)
          Nothing -> return ()

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



data Command
  = AlertBadInput String
  | InsertString String
  | KillLastWord
  | KillLastChar
  | KillNextChar
  | ExecuteInputBuffer
  | MotionCommand LeftRightMotion
  | ChangeMode Mode
  -- TODO Move Count Motion
  --      Delete Count Register Motion
  --      etc.
  | Combine Command Command
  | Nop
  | RingBell

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 e = rec e
  where
    color cc s = "\x1b[" ++ cc ++ "m" ++ s ++ "\x1b[m"

    rec (UnhandledInputError s) =
      color "31" $ "unhandled input: <" ++ (pp "31;1" s) ++ "\x1b[;31m>"

    rec (OtherError s) =
      color "31" $ "error: " ++ s

    -- TODO cc is ColorCode
    pp cc = concat . map (pp1 cc)
    pp1 cc c
      | isPrint c = [c]
      | otherwise = specialChar cc $
        case c of
          '\x1b' -> "^["
          _ -> charToCode c
    specialChar cc s = "\x1b[1;35m" ++ s ++ "\x1b[;" ++ cc ++ "m"




modifyBuffer :: (Buffer -> Buffer) -> VT ()
modifyBuffer f =
    modify $ \st -> st { buffer = f (buffer st) }



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 s (ls, rs) = (ls ++ s, rs)


execCommand :: Command -> VT ()

execCommand (MotionCommand x) = do
    modifyBuffer (move x)
    -- TODO apply mode constraints somewhere else
    q <- get
    when (mode q == NormalMode) $
      when (null $ snd $ buffer q) $
        modifyBuffer (gotoLeft 1)

execCommand (ChangeMode m) =
    modify $ \ q -> q { mode = m }

execCommand (InsertString s) =
    modifyBuffer (insertString s)

execCommand ExecuteInputBuffer = do
    b <- gets buffer
    tell [ "input: <" ++ (concat $ map (reform 32) $ showBuffer b) ++ ">" ]
    modifyBuffer (const emptyBuffer)

execCommand KillNextChar = do
    get >>= flip (when . null . snd . buffer)
                 (throwError $ OtherError "nothing to kill right")
    modifyBuffer $ \(lhs, _:rhs') -> (lhs, rhs')

execCommand KillLastChar = do
    get >>= flip (when . null . fst . buffer)
                 (throwError $ OtherError "nothing to kill left")
    modifyBuffer $ \(lhs, rhs) -> (init lhs, rhs)

execCommand KillLastWord = do
    get >>= flip (when . null . fst . buffer)
                 (throwError $ OtherError "nothing to kill left")
    modifyBuffer $
      \(lhs, rhs) -> (foldr dropWhileEnd lhs [not . isSpace, isSpace], rhs)

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


reform colorCode c =
    if isPrint c
      then normal colorCode [c]
      else
        special colorCode $
          case ord c of
            27 -> "^["
            _ -> charToCode c

normal colorCode s = "\x1b[" ++ show colorCode ++ "m" ++ s ++ "\x1b[m"
special colorCode s = "\x1b[1;" ++ show colorCode ++ "m" ++ s ++ "\x1b[m"



-- XXX assumes that the cursor is already at the (cleared) input line
renderInputLine :: Mode -> Buffer -> IO ()
renderInputLine m (lhs, rhs) = do
    clearLine -- TODO this is required for drawing the mode on the right side
    saveCursor
    moveCursorRight 1024
    moveCursorLeft (length (show m) - 1)
    putStr $ "\x1b[1;30m" ++ show m ++ "\x1b[m"
    unsaveCursor

    let promptString = case m of
                        NormalMode -> "\x1b[33;1m@\x1b[m "
                        InsertMode -> "> "

    putStr $ promptString ++ pp lhs ++ pp rhs
    moveCursorLeft (length $ ppVis rhs)
  where
    pp = concat . map reform
    reform c =
      if isPrint c
        then [c]
        else
          "\x1b[35m" ++ (
            case ord c of
              27 -> "^["
              _ -> charToCode c
          ) ++ "\x1b[m"

    ppVis = concat . map reformVis
    reformVis c =
      if isPrint c
        then [c]
        else
            case ord c of
              27 -> "^["
              _ -> charToCode c






clearLine =
    putStr "\x1b[2K" >>
    moveCursorLeft 1024


ringBell = putStr "\x07" -- BEL '\a'


saveCursor = putStr "\x1b[s"
unsaveCursor = putStr "\x1b[u"


moveCursorLeft 0 = return ()
moveCursorLeft i = putStr $ "\x1b[" ++ show i ++ "D"


moveCursorRight 0 = return ()
moveCursorRight i = putStr $ "\x1b[" ++ show i ++ "C"


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



nmap =
  [ ("i", ChangeMode InsertMode)
  , ("a", ChangeMode InsertMode <> MotionCommand (GotoRight 1))
  , ("I", ChangeMode InsertMode <> MotionCommand GotoFirstChar)
  , ("A", ChangeMode InsertMode <> MotionCommand GotoEndOfLine)
  , ("0", MotionCommand GotoFirstChar)
  , ("$", MotionCommand GotoEndOfLine)
  , ("h", MotionCommand $ GotoLeft 1)
  , ("l", MotionCommand $ GotoRight 1)
  , ("b", MotionCommand $ WordsBackward 1)
  , ("w", MotionCommand $ WordsForward 1)
  , ("\x1b[C", MotionCommand $ GotoRight 1)
  , ("\x1b[D", MotionCommand $ GotoLeft 1)
  , ("\x0a", ExecuteInputBuffer <> ChangeMode InsertMode)
  , ("\x1b", RingBell) -- TODO cancel any unfinished commands
  ]


imap =
  [ ("\x1b", ChangeMode NormalMode <> MotionCommand (GotoLeft 1))
  , ("\x01", MotionCommand GotoFirstChar)
  , ("\x05", MotionCommand GotoEndOfLine)
  , ("\x1b[3~", KillNextChar)
  , ("\x1b[C", MotionCommand $ GotoRight 1)
  , ("\x1b[D", MotionCommand $ GotoLeft 1)
  , ("\x16", ChangeMode VerbatimMode) -- ^V
  , ("\x17", KillLastWord) -- ^W
  , ("\x0a", ExecuteInputBuffer)
  , ("\x7f", KillLastChar) -- Delete
  , ("\x08", KillLastChar) -- BackSpace
  , ("\x1bOc", MotionCommand $ WordsForward 1)
  , ("\x1bOd", MotionCommand $ WordsBackward 1)
  ]


type Keymap = [(String, Command)]

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

instance  Show Mode  where
  show NormalMode = "normal"
  show InsertMode = "insert"
  show VerbatimMode = "verbatim"


getCommand :: Mode -> VT Command
getCommand InsertMode = getCommandXXX imap InsertString
getCommand NormalMode = getCommandXXX nmap AlertBadInput
getCommand VerbatimMode = verbatimKeymap


-- TODO refactor me please^_^
getCommandXXX :: Keymap -> (String -> Command) -> VT Command
getCommandXXX keymap defCmd = do

    -- wait for the first character
    c <- liftIO $ hLookAhead stdin

    bufRef <- liftIO $ newIORef ""
    candRef <- liftIO $ newIORef Nothing
    cmdRef <- liftIO $ newEmptyMVar -- :: MVar (Maybe (String -> Command))

    -- TODO ensure that this thread dies eventually
    --forkIO $ rec "" keymap cmdRef candRef
    getCharThreadId <-
        --forkFinally (rec keymap cmdRef candRef bufRef)
        --            (\_ -> putStrLn "input terminated")
        liftIO $ forkIO $ do
          rec keymap cmdRef candRef bufRef

    watchDogThreadId <-
        liftIO $ forkIO $ do
          --putStrLn "watchdog activated"
          threadDelay $ 1000 * 50 -- 50ms
          --putStrLn "watchdog timeout"
          killThread getCharThreadId
          --putStrLn "watchdog killed getCharThread"
          putMVar cmdRef Nothing -- continue main thread

    mbCmd <- liftIO $ takeMVar cmdRef

    liftIO $ killThread watchDogThreadId

    cmd <- case mbCmd of
        Just cmd -> return cmd
        Nothing -> do
            mbCmd2 <- liftIO $ readIORef candRef
            case mbCmd2 of
                Just cmd2 -> return cmd2
                Nothing -> return defCmd

    s <- liftIO $ readIORef bufRef

    --clearLine
    --putStrLn $ "\x1b[35;1m" ++ (show s) ++ " -> " ++ (show $ cmd s) ++ "\x1b[m"
    return $ cmd s

  where
    rec :: Keymap
        -> MVar (Maybe (String -> Command))
        -> IORef (Maybe (String -> Command))
        -> IORef String
        -> IO ()
    rec km cmdRef candRef bufRef = do
        c <- getChar
        -- TODO s <- atomicModifyIORef bufRef $ \s -> let s' = s++[c] in (s,s)
        olds <- readIORef bufRef
        let s = olds ++ [c]
        writeIORef bufRef s

        let km' = map (\(str,cmd) -> (tail str, cmd))
                $ filter ((==c) . head . fst) km

            -- direct and indirect candidates
            (dc, ic) = partition (null . fst) km'

        --clearLine
        --putStrLn $ " s: " ++ show s
        --putStrLn $ "ic: " ++ (show $ map snd ic)
        --putStrLn $ "dc: " ++ (show $ map snd dc)

        -- update candidate
        if length dc == 1
          then atomicWriteIORef candRef (Just $ const $ snd $ dc !! 0)
          else atomicWriteIORef candRef Nothing

        case length km' of
          0 -> do
            --return $ defCmd' (s ++ [c])
            cand <- readIORef candRef
            putMVar cmdRef cand
          1 ->
            let (rest, cmd) = km' !! 0
            in if null rest
                then do
                  --return $ cmd
                  -- TODO somehow give s?
                  putMVar cmdRef (Just $ const cmd)
                else do
                  --rec (s ++ [c]) ic defCmd'
                  rec ic cmdRef candRef bufRef
          _ -> do
            --rec (s ++ [c]) ic defCmd'
            rec ic cmdRef candRef bufRef



verbatimKeymap :: VT Command
verbatimKeymap = do
  c <- liftIO getChar
  return $ InsertString [c] <> ChangeMode InsertMode


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