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

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

import GHC.Stats (getRTSStats)

import Control.Monad.Except
import Control.Monad.Reader
import Control.Monad.State
import Control.Monad.Writer

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

import Hack.Buffer
import Process
import Scanner
import Blessings
import qualified Blessings.Internal as Blessings
import Blessings.String ()


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

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


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

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

instance Show VTState where
    show VTState{..} =
      "<VTState"
      ++ " buffer=" ++ show _buffer
      ++ " mode=" ++ show _mode
      ++ " processCount=" ++ show _processCount
      ++ " count=" ++ show (maybe 0 id _count)
      ++ " register=" ++ show _register
      ++ " registers=" ++ show _registers
      ++ ">"

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
    s <- scan stdin
    --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 ScanKey k = s
    let cmd = getCommand (_mode q0) k

    --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
  | DebugShowVTState
  | InsertString String
  | ExecuteInputBuffer
  | MoveCursor Motion
  | MoveCursorLeftIfAtEndOfLine
  | MoveCursorWarn Motion
  | ChangeMode Mode
  -- TODO Move Count Motion
  --      Delete Count Register Motion
  --      etc.
  | Combine Command Command
  | Nop
  | RingBell
  | AppendCount Int
  | SetCount (Maybe Int)
  | SetRegister Char
  | Delete Motion
  | DeleteEntireLine
  | Yank Motion


instance Semigroup Command where
    (<>) = Combine


instance Monoid Command where
    mempty = Nop



data ExecError
  = UnhandledInputError String
  | OtherError String


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
        (ExceptT 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 (runExceptT (runReaderT a cf))) st



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


execCommand :: Command -> VT ()

execCommand DebugShowVTState =
    get >>= tell . (:[]) . pp . SGR [35] . Plain . show

execCommand (MoveCursor 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 merge with mode constraints in MoveCursor
execCommand MoveCursorLeftIfAtEndOfLine = do
    whenM (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 (MoveCursorWarn x) = do
    b0 <- use buffer
    execCommand (MoveCursor 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 getRTSStats
          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 (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)

-- TODO yank into "- (smallDeleteRegister) when deleting less than one line
-- TODO reset register after this command (q & register .~ defaultRegister)
execCommand (Delete x) = do
    b0 <- use buffer
    c <- uses count (maybe 1 id)
    buffer %= delete x c
    b1 <- use buffer

    when (b0 == b1) $ throwError (OtherError "nothing to delete")


-- TODO Yank register motion (after motion has incorporated count)
execCommand (Yank x) =
    modify $ \q@VTState{..} -> do
        let c = maybe 1 id _count
            y = select x c _buffer

        q & registers %~ (at _register .~ Just y)


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


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



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


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 :: Pm -> (Char -> Bool) -> String -> Blessings String
gaudySpans c p =
    mconcat . map (either (SGR c . Plain . lit) Plain) . spans p


gaudySpecial :: Pm -> String -> Blessings String
gaudySpecial c = gaudySpans c (not . isPrint)


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


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


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


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

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


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


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


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


dmap :: Keymap
dmap =
  [ ("\ESC", ChangeMode NormalMode <> SetCount Nothing)
  , ("\ESC[24~", DebugShowVTState)
  , ("d", DeleteEntireLine <> ChangeMode NormalMode <> SetCount Nothing)
  , ("$", Yank ToEndOfLine <>
          Delete ToEndOfLine <>
          ChangeMode NormalMode <>
          SetCount Nothing <>
          MoveCursorLeftIfAtEndOfLine
          )
  , ("0", Yank ToStartOfLine <>
          Delete ToStartOfLine <>
          ChangeMode NormalMode <> SetCount Nothing)
  , ("h", Yank CharsBackward <>
          Delete CharsBackward <>
          ChangeMode NormalMode <> SetCount Nothing)
  , ("l", Yank CharsForward <>
          Delete CharsForward <>
          ChangeMode NormalMode <>
          SetCount Nothing <>
          MoveCursorLeftIfAtEndOfLine
          )
  ]


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


-- TODO maybe in normal mode reset count (SetCount Nothing) after each
-- command doesn't alter the count. How would this work together with
-- ChangeMode DeleteMode
-- TODO 2017-08-06
--  initialize count whenever nmap is entered
--  ditch SetCount Nothing
--  pass count to commands / modes
nmap :: Keymap
nmap =
  [ ("\ESC", SetCount Nothing)
            -- ^TODO RingBell if count is already Nothing
            --  TODO cancel any unfinished commands
  , ("i", ChangeMode InsertMode <> SetCount Nothing)
  , ("a", ChangeMode InsertMode <> SetCount Nothing <> MoveCursor CharsForward)
  , ("I", ChangeMode InsertMode <> MoveCursor ToStartOfLine)
  , ("A", ChangeMode InsertMode <> MoveCursor ToEndOfLine)
  , ("|", MoveCursorWarn ToColumn <> SetCount Nothing)
  , ("$", MoveCursorWarn ToEndOfLine <> SetCount Nothing)
  , ("h", MoveCursorWarn CharsBackward <> SetCount Nothing)
  , ("l", MoveCursorWarn CharsForward <> SetCount Nothing)
  , ("b", MoveCursorWarn WordsBackward <> SetCount Nothing)
  , ("w", MoveCursorWarn WordsForward <> SetCount Nothing)
  , ("d", ChangeMode DeleteMode)
  , ("y", ChangeMode YankMode)
  , ("\"", ChangeMode SelectRegisterMode <> SetCount Nothing)
  , ("\ESC[24~", DebugShowVTState)
  , ("\ESC[C", MoveCursorWarn CharsForward <> SetCount Nothing)
  , ("\ESC[D", MoveCursorWarn CharsBackward <> SetCount Nothing)
  , ("\n", 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 (MoveCursor ToStartOfLine) (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 =
  [ ("\ESC", ChangeMode NormalMode <> MoveCursor CharsBackward)
  , ("\x01", MoveCursorWarn ToStartOfLine)
  , ("\x05", MoveCursorWarn ToEndOfLine)
  , ("\ESC[24~", DebugShowVTState)
  , ("\ESC[3~", Delete CharsForward)
  , ("\ESC[C", MoveCursorWarn CharsForward)
  , ("\ESC[D", MoveCursorWarn CharsBackward)
  , ("\x16", ChangeMode VerbatimMode) -- ^V
  , ("\x17", Delete WordsBackward) -- ^W
  , ("\x0a", ExecuteInputBuffer)
  , ("\x7f", Delete CharsBackward) -- Delete
  , ("\x08", Delete CharsBackward) -- BackSpace
  , ("\ESCOc", MoveCursorWarn WordsForward)
  , ("\ESCOd", MoveCursorWarn WordsBackward)
  ]

ymap :: Keymap
ymap =
  [ ("\ESC", ChangeMode NormalMode <> SetCount Nothing)
  , ("\ESC[24~", DebugShowVTState)
  -- TODO , ("y", DeleteEntireLine <> ChangeMode NormalMode <> SetCount Nothing)
  , ("$", Yank ToEndOfLine <> ChangeMode NormalMode <> SetCount Nothing)
  , ("0", Yank ToStartOfLine <> ChangeMode NormalMode <> SetCount Nothing)
  , ("h", Yank CharsBackward <> ChangeMode NormalMode <> SetCount Nothing)
  , ("l", Yank CharsForward <> ChangeMode NormalMode <> SetCount Nothing)
  ]


type Keymap = [(String, Command)]


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

getCommand YankMode s = maybe (AlertBadInput s) id $ lookup s ymap


-- 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