{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Main where

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)


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

data VTState = VTState
    { buffer :: Buffer
    , mode :: Mode
    , processCount :: Int
    , count :: Maybe Int
    , register :: Char
    , registers :: Map Char String
    }

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

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

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

    -- TODO cc is ColorCode
    pp 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 :: String -> Buffer -> Buffer
insertString s (ls, rs) = (ls ++ s, rs)


execCommand :: Command -> VT ()

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

execCommand (MotionCommandWarn x) = do
    b0 <- gets buffer
    execCommand (MotionCommand x)
    b1 <- gets buffer

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

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

execCommand (InsertString s) =
    modifyBuffer (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
      ":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 <- state $ \ q ->
              let i = processCount q + 1
              in (i, q { processCount = i })
          cf <- ask
          liftIO $ forkIO $ spawn i (withOutput cf) cmdline
          return ()
      "" -> do
          liftIO ringBell
      s -> do
          tell [ "input: <" ++ (s >>= reform 32) ++ ">" ]

    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

execCommand (AppendCount i) =
    modify $ \q -> q { count = f (count q) }
  where
    f Nothing = Just i
    f (Just c) = Just (c * 10 + i)

execCommand (SetCount i) =
    modify $ \q -> q { count = i }

execCommand (SetRegister c) = modify $ \q -> q { register = c }

execCommand DeleteEntireLine = modify $ \q ->
    -- TODO Numbered registers "0 to "9
    --      Small delete register "-
    let s = showBuffer $ buffer q
        r = register q
    in q { registers = Map.insert r s
                     $ Map.insert defaultRegister s
                     $ registers q
         , buffer = emptyBuffer
         , register = defaultRegister
         }


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

normal :: Int -> String -> String
normal colorCode s = "\x1b[" ++ show colorCode ++ "m" ++ s ++ "\x1b[m"

special :: Int -> String -> String
special colorCode s = "\x1b[1;" ++ show colorCode ++ "m" ++ s ++ "\x1b[m"



-- 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
    clearLine -- TODO this is required for drawing the mode on the right side
    saveCursor
    moveCursorRight 1024
    let (infoLen, info) =
          case mb_cnt of
              Nothing ->
                  let gaudy = "\x1b[1;30m" ++ show m ++ "\x1b[m"
                      plain = show m
                  in (length plain, gaudy)
              Just cnt ->
                  let gaudy = "\x1b[1;30m" ++ show m ++
                              "[\x1b[33m" ++ show cnt ++ "\x1b[30m]\x1b[m"
                      plain = show m ++ "[" ++ show cnt ++ "]"
                  in (length plain, gaudy)
    moveCursorLeft $ infoLen - 1
    putStr info
    unsaveCursor

    let promptString = case m of
                        NormalMode -> "\x1b[33;1m@\x1b[m "
                        InsertMode -> "> "
                        VerbatimMode -> "\x1b[34;1m^\x1b[m "
                        SelectRegisterMode -> "\" "
                        DeleteMode -> "\x1b[31;1m>\x1b[m "

    putStr $ promptString ++ (lhs >>= reform') ++ (rhs >>= reform')
    moveCursorLeft (length $ rhs >>= reformVis)
  where
    -- TODO unify reform and reform'
    reform' c =
      if isPrint c
        then [c]
        else
          "\x1b[35m" ++ (
            case ord c of
              27 -> "^["
              _ -> charToCode c
          ) ++ "\x1b[m"

    reformVis c =
      if isPrint c
        then [c]
        else
            case ord c of
              27 -> "^["
              _ -> charToCode 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)
  , ("|", MotionCommand GotoColumn <> SetCount Nothing)
  , ("$", MotionCommand GotoEndOfLine <> SetCount Nothing)
  , ("h", MotionCommand GotoLeft <> SetCount Nothing)
  , ("l", MotionCommand GotoRight <> SetCount Nothing)
  , ("b", MotionCommand WordsBackward <> SetCount Nothing)
  , ("w", MotionCommand WordsForward <> SetCount Nothing)
  , ("d", ChangeMode DeleteMode <> SetCount Nothing)
  , ("\"", ChangeMode SelectRegisterMode <> SetCount Nothing)
  , ("\x1b[C", MotionCommand GotoRight <> SetCount Nothing)
  , ("\x1b[D", MotionCommand 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", MotionCommand GotoFirstChar)
  , ("\x05", MotionCommand GotoEndOfLine)
  , ("\x1b[3~", KillNextChar)
  , ("\x1b[C", MotionCommand GotoRight)
  , ("\x1b[D", MotionCommand GotoLeft)
  , ("\x16", ChangeMode VerbatimMode) -- ^V
  , ("\x17", KillLastWord) -- ^W
  , ("\x0a", ExecuteInputBuffer)
  , ("\x7f", KillLastChar) -- Delete
  , ("\x08", KillLastChar) -- BackSpace
  , ("\x1bOc", MotionCommand WordsForward)
  , ("\x1bOd", MotionCommand WordsBackward)
  ]


type Keymap = [(String, Command)]

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

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 ()