{-# 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 :: 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 = 0
          , 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 (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

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

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

    -- XXX dummy for following legacy code
    let eitCmd = Right cmd

    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 cf $ do
        forM_ lns 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
  | AddCount Int
  | MulCount Int
  | SetCount Int
  | SetRegister Char

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
    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

    ---- 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 (AddCount i) = modify $ \q -> q { count = i + count q }
execCommand (MulCount i) = modify $ \q -> q { count = i * count q }
execCommand (SetCount i) = modify $ \q -> q { count = i }

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


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
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 -> "> "
                        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)
  ]


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


nmap :: Keymap
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)
  , ("d", ChangeMode DeleteMode)
  , ("\"", ChangeMode SelectRegisterMode)
  , ("\x1b[C", MotionCommand $ GotoRight 1)
  , ("\x1b[D", MotionCommand $ GotoLeft 1)
  , ("\x0a", ExecuteInputBuffer <> ChangeMode InsertMode)
  , ("\x1b", RingBell) -- TODO cancel any unfinished commands
  ]
  ++ (map (\i -> (show i, MulCount 10 <> AddCount i)) [0..9])


imap :: Keymap
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
  | 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) 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 ()