{-# 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 (NormalMode nmap)



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

  tid <- myThreadId

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

  lock <- newMVar emptyBuffer

  renderInputLine emptyBuffer
  hFlush stdout

  forkIO $ (dateThread 1000000) lock
  uiThread (NormalMode nmap) lock


dateThread delay lock = forever $ do
    t <- getCurrentTime
    withMVar lock $ \ buf -> do
      clearLine
      putStrLn $ formatTime defaultTimeLocale rfc822DateFormat t
      renderInputLine buf
      hFlush stdout
    threadDelay delay


uiThread mod lock = do
    c <- getCommand mod
    mod' <- modifyMVar lock $ \ buf -> do
        let st = VTState
                { mode = mod
                , 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 (show (mode st) /= show (mode st')) $ do
            putStrLn $ "change mode: " ++ (show $ mode st')

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

    uiThread mod' lock


data Command
  = AlertBadInput String
  | InsertChar Char
  | InsertNextCharVerbatim
  | InsertCharThenChangeMode Char Mode
  | KillLastWord
  | KillLastChar
  | KillNextChar
  | ExecuteInputBuffer
  | UnboundSequence String String
  | MotionCommand LeftRightMotion
  -- TODO Move Count Motion
  --      Delete Count Register Motion
  --      etc.


data ExecError
  = UnboundSequenceError String String
  | 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 (UnboundSequenceError s n) =
      color "31" $ "unbound sequence: <" ++ (pp "31;1" s) ++ "\x1b[;31m> "
                  ++ (pp "31;1" n)

    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



insertChar c (ls, rs) = (ls ++ [c], rs)


execCommand :: Command -> ExecM ()

execCommand (MotionCommand x) =
    modifyBuffer (move x)

execCommand (InsertChar c) =
    modifyBuffer (insertChar c)

execCommand (InsertCharThenChangeMode c m) =
    modify $ \ q -> q
      { mode = m
      , buffer = insertChar c (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 (UnboundSequence s n) =
    throwError (UnboundSequenceError s n)






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 :: Buffer -> IO ()
renderInputLine (lhs, rhs) = do
    putStr $ "> " ++ 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 80


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


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


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





-- TODO pressing ESC, then F11 etc. is ugly
nmap =
  [ ("\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

  -- TODO replace by backward-word
  --                 forward-word
  -- OR
  --    [MotionCommand SkipSpaceRight, MotionCommand $ GotillFindRight 1 ' ']
  --    etc.
  , ("\x1bOc", MotionCommand $ WordsForward 1)
  , ("\x1bOd", MotionCommand $ WordsBackward 1)
  ]
  ++ [unboundSequence "\x1b[2~" "<Insert>"]
  ++ [unboundSequence "\x1b[5~" "<Prior>"]    -- page up
  ++ [unboundSequence "\x1b[6~" "<Next>"]     -- page dn
  ++ [unboundSequence "\x1b[7~" "<Home>"]
  ++ [unboundSequence "\x1b[8~" "<End>"]
  ++ [unboundSequence "\x1b[2$" "<S-Insert>"]
  ++ [unboundSequence "\x1b[5$" "<S-Prior>"]    -- page up
  ++ [unboundSequence "\x1b[6$" "<S-Next>"]     -- page dn
  ++ [unboundSequence "\x1b[7$" "<S-Home>"]
  ++ [unboundSequence "\x1b[8$" "<S-End>"]
  ++ [unboundSequence "\x1b\x1b[2$" "<S-M-Insert>"]
  ++ [unboundSequence "\x1b\x1b[5$" "<S-M-Prior>"]    -- page up
  ++ [unboundSequence "\x1b\x1b[6$" "<S-M-Next>"]     -- page dn
  ++ [unboundSequence "\x1b\x1b[7$" "<S-M-Home>"]
  ++ [unboundSequence "\x1b\x1b[8$" "<S-M-End>"]
  ++ [unboundSequence "\x1b\x1b[A" "<M-Up>"]
  ++ [unboundSequence "\x1b\x1b[B" "<M-Down>"]
  ++ [unboundSequence "\x1b\x1b[C" "<M-Right>"]
  ++ [unboundSequence "\x1b\x1b[D" "<M-Left>"]
  ++ [unboundSequence "\x1b\x1b[a" "<S-M-Up>"]
  ++ [unboundSequence "\x1b\x1b[b" "<S-M-Down>"]
  ++ [unboundSequence "\x1b\x1b[c" "<S-M-Right>"]
  ++ [unboundSequence "\x1b\x1b[d" "<S-M-Left>"]
  ++ [unboundSequence "\x1b[a" "<S-Up>"]
  ++ [unboundSequence "\x1b[b" "<S-Down>"]
  ++ [unboundSequence "\x1b[c" "<S-Right>"]
  ++ [unboundSequence "\x1b[d" "<S-Left>"]
  ++ [unboundSequence "\x1bOa" "<C-Up>"]
  ++ [unboundSequence "\x1bOb" "<C-Down>"]
  ++ [unboundSequence "\x1bOc" "<C-Right>"]
  ++ [unboundSequence "\x1bOd" "<C-Left>"]
  ++ [unboundSequence "\x1b\x1bOa" "<C-M-Up>"]
  ++ [unboundSequence "\x1b\x1bOb" "<C-M-Down>"]
  ++ [unboundSequence "\x1b\x1bOc" "<C-M-Right>"]
  ++ [unboundSequence "\x1b\x1bOd" "<C-M-Left>"]
  ++ [unboundSequence "\x1b[11~" "<F1>"]
  ++ [unboundSequence "\x1b[12~" "<F2>"]
  ++ [unboundSequence "\x1b[13~" "<F3>"]
  ++ [unboundSequence "\x1b[14~" "<F4>"]
  ++ [unboundSequence "\x1b[15~" "<F5>"]
  ++ [unboundSequence "\x1b[17~" "<F6>"]
  ++ [unboundSequence "\x1b[18~" "<F7>"]
  ++ [unboundSequence "\x1b[19~" "<F8>"]
  ++ [unboundSequence "\x1b[20~" "<F9>"]
  ++ [unboundSequence "\x1b[21~" "<F10>"]
  ++ [unboundSequence "\x1b[23~" "<F11>"]
  ++ [unboundSequence "\x1b[24~" "<F12>"]

  ++ [unboundSequence "\x1b\x1b[2~" "<M-Insert>"]
  ++ [unboundSequence "\x1b\x1b[3~" "<M-Delete>"]
  ++ map (\ i -> unboundSequence ("\x1b\x1b[" ++ show i ++ "~")
                                 ("<M-F" ++ show i ++ ">"))
          [11..24]
  ++ [unboundSequence "\x1b\x7f" "<M-BackSpace>"]
  ++ [unboundSequence "\x1b\x0a" "<M-Return>"]


unboundSequence seq name =
  (seq, UnboundSequence seq name)


data Mode
  = NormalMode [(String, Command)]
  | VerbatimMode

instance  Show Mode  where
  show (NormalMode _) = "normal"
  show VerbatimMode = "verbatim"


getCommand :: Mode -> IO Command
getCommand (NormalMode map) = getMappedCommand map
getCommand VerbatimMode = verbatimKeymap


getMappedCommand :: [(String, Command)] -> IO Command
getMappedCommand xs = do
    c <- getChar
    if any (isPrefixOf [c] . fst) xs
      then rec [c]
      else
        if isPrint c
          then return $ InsertChar 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 $ InsertCharThenChangeMode c defaultGetCommand
  return $ InsertCharThenChangeMode c (NormalMode nmap)


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