{-# 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.Writer
import Control.Monad.State

import Buffer


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

emptyState = VTState emptyBuffer InsertMode



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

  tid <- myThreadId

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

  modeRef <- newIORef InsertMode
  lock <- newMVar emptyBuffer

  renderInputLine InsertMode emptyBuffer
  hFlush stdout

  forkIO $ dateThread 1000000 modeRef lock
  uiThread modeRef lock


dateThread :: Int -> IORef Mode -> MVar Buffer -> IO ()
dateThread delay modeRef lock = forever $ do
    t <- getCurrentTime
    m <- readIORef modeRef
    withMVar lock $ \ buf -> do
      clearLine
      putStrLn $ formatTime defaultTimeLocale rfc822DateFormat t
      renderInputLine m buf
      hFlush stdout
    threadDelay delay


uiThread modeRef lock = do
    m <- readIORef modeRef
    c <- getCommand m
    m' <- modifyMVar lock $ \ buf -> do
        let st = VTState
                { mode = m
                , buffer = buf
                }

        ((eSt, lines), st') <- runExecCommand st (execCommand c)

        clearLine
        forM_ lines putStrLn

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

        -- TODO move this to execCommand / throwError
        case c of
          MotionCommand motion ->
            when (buffer st == buffer st') $
              ringBell >>
              putStrLn (prettyError $ OtherError $ "motion failed: " ++ show motion)
          _ -> return ()


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

        renderInputLine (mode st') (buffer st')
        hFlush stdout
        return (buffer st', mode st')

    writeIORef modeRef m'
    uiThread modeRef lock


data Command
  = AlertBadInput String
  | InsertString String
  | InsertNextCharVerbatim
  | InsertStringThenChangeMode String Mode
  | 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) -> ExecM ()
modifyBuffer f =
    modify $ \st -> st { buffer = f (buffer st) }



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

runExecCommand ::
    VTState -> ExecM a -> IO ((Either ExecError a, [String]), VTState)

runExecCommand st (ExecM ex) =
    runStateT (runWriterT (runErrorT ex)) st



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


execCommand :: Command -> ExecM ()

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 (InsertStringThenChangeMode s m) =
    modify $ \ q -> q
      { mode = m
      , buffer = insertString s (buffer q)
      }

execCommand InsertNextCharVerbatim =
    modify $ \ q -> q
      { mode = VerbatimMode
      }

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
    q0 <- get

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

    -- TODO "stack trace"
    whenLeft eSt1 throwError

    ((eSt2, lines2), q2) <- liftIO $ runExecCommand 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)
  , ("\x0a", ExecuteInputBuffer <> ChangeMode InsertMode)
  ]


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", InsertNextCharVerbatim) -- ^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 -> IO Command
getCommand InsertMode = getMappedCommand imap (InsertString . (:[]))
getCommand NormalMode = getMappedCommand nmap (AlertBadInput . (:[]))
getCommand VerbatimMode = verbatimKeymap


getMappedCommand :: Keymap -> (Char -> Command) -> IO Command
getMappedCommand xs defCmd = do
    c <- getChar
    if any (isPrefixOf [c] . fst) xs
      then rec [c]
      else
        if isPrint c
          then return $ defCmd c
          else return $ AlertBadInput [c]
  where
    rec :: String -> IO Command
    rec s =
      case lookup s xs of
        Just c -> return c
        _ ->
          if any (isPrefixOf s . fst) xs
            then do
              c <- getChar
              rec $ s ++ [c]
            else
              return $ AlertBadInput s


verbatimKeymap :: IO Command
verbatimKeymap = do
  c <- getChar
  return $ InsertStringThenChangeMode [c] NormalMode


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