module Vere.Term
    ( TerminalSystem(..)
    , initializeLocalTerminal
    , term
    , tsHideSpinner
    , tsShowSpinner
    , tsStderr
    ) where

import Arvo                  hiding (Term)
import Data.Char
import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable
import RIO.FilePath
import System.Posix.IO
import System.Posix.Terminal
import Urbit.Time
import UrbitPrelude          hiding (getCurrentTime)
import Vere.Pier.Types

import Data.List     ((!!))
import RIO.Directory (createDirectoryIfMissing)

import qualified Data.ByteString.Internal     as BS
import qualified Data.ByteString.UTF8         as BS
import qualified System.Console.Terminfo.Base as T

-- External Types --------------------------------------------------------------

{-
    Input Event for terminal driver:

    %blits -- list of blits from arvo.
    %trace -- stderr line from runtime.
    %blank -- print a blank line
    %spinr -- Start or stop the spinner
-}
data DrvEv = DEBlits [Blit]
           | DETrace Text
           | DEBlank
           | DESpinr (Maybe (Maybe Text))

{-
    Minimal terminal interface.

    A Terminal can either be local or remote. Either way, the Terminal,
    from the view of the caller, a terminal has a thread which when
    exits indicates that the session is over, and has a general in/out
    queue in the types of the vere/arvo interface.
-}
data TerminalSystem = TerminalSystem
  { tsRead  :: STM Belt
  , tsWrite :: DrvEv -> STM ()
  }

tsStderr :: TerminalSystem -> Text -> STM ()
tsStderr ts = tsWrite ts . DETrace

tsShowSpinner :: TerminalSystem -> Maybe Text -> STM ()
tsShowSpinner ts = tsWrite ts . DESpinr . Just

tsHideSpinner :: TerminalSystem -> STM ()
tsHideSpinner ts = tsWrite ts (DESpinr Nothing)



-- Types -----------------------------------------------------------------------

-- All stateful data in the printing to stdOutput.
data LineState = LineState
  { lsLine            :: Text
  , lsCurPos          :: Int
  , lsSpinTimer       :: Maybe (Async ())
  , lsSpinCause       :: Maybe Text
  , lsSpinFirstRender :: Bool
  , lsSpinFrame       :: Int
  , lsPrevEndTime     :: Wen
  }

-- A record used in reading data from stdInput.
data ReadData = ReadData
  { rdBuf       :: Ptr Word8
  , rdEscape    :: Bool
  , rdBracket   :: Bool
  , rdUTF8      :: ByteString
  , rdUTF8width :: Int
  }

-- Private data to the TerminalSystem that we keep around for stop().
data Private = Private
  { pReaderThread          :: Async ()
  , pWriterThread          :: Async ()
  , pPreviousConfiguration :: TerminalAttributes
  }

-- Utils -----------------------------------------------------------------------

termText :: Text -> T.TermOutput
termText = T.termText . unpack

initialBlew w h = EvBlip $ BlipEvTerm $ TermEvBlew (UD 1, ()) w h

initialHail = EvBlip $ BlipEvTerm $ TermEvHail (UD 1, ()) ()

-- Version one of this is punting on the ops_u.dem flag: whether we're running
-- in daemon mode.

spinners :: [Text]
spinners = ["|", "/", "-", "\\"]

leftBracket :: Text
leftBracket = "«"

rightBracket :: Text
rightBracket = "»"

_spin_cool_us = 500000
_spin_warm_us = 50000
_spin_rate_us = 250000
_spin_idle_us = 500000

--------------------------------------------------------------------------------

runMaybeTermOutput :: T.Terminal -> (T.Terminal -> Maybe T.TermOutput) -> RIO e ()
runMaybeTermOutput t getter = case (getter t) of
  Nothing -> pure ()
  Just x  -> io $ T.runTermOutput t x

rioAllocaBytes :: (MonadIO m, MonadUnliftIO m)
               => Int -> (Ptr a -> m b) -> m b
rioAllocaBytes size action =
  withRunInIO $ \run ->
    allocaBytes size $ \x -> run (action x)

-- Because of legacy reasons, some file operations are in the terminal
-- driver. These should be filtered out and handled locally instead of in any
-- abstractly connected terminal.
isTerminalBlit :: Blit -> Bool
isTerminalBlit (Sav _ _) = False
isTerminalBlit (Sag _ _) = False
isTerminalBlit _         = True

--------------------------------------------------------------------------------

-- Initializes the generalized input/output parts of the terminal.
--
initializeLocalTerminal :: forall e. HasLogFunc e
                        => RAcquire e TerminalSystem
initializeLocalTerminal = fst <$> mkRAcquire start stop
  where
    start :: HasLogFunc e => RIO e (TerminalSystem, Private)
    start = do
      --  Initialize the writing side of the terminal
      --
      t <- io $ T.setupTermFromEnv
      -- TODO: We still need to actually get the size from the terminal somehow.

      tsWriteQueue <- newTQueueIO
      spinnerMVar <- newEmptyTMVarIO
      pWriterThread <- asyncBound (writeTerminal t tsWriteQueue spinnerMVar)

      pPreviousConfiguration <- io $ getTerminalAttributes stdInput

      -- Create a new configuration where we put the terminal in raw mode and
      -- disable a bunch of preprocessing.
      let newTermSettings =
            flip withTime     0 .
            flip withMinInput 1 $
            foldl' withoutMode pPreviousConfiguration disabledFlags
      io $ setTerminalAttributes stdInput newTermSettings Immediately

      tsReadQueue <- newTQueueIO
      pReaderThread <- asyncBound
          (readTerminal tsReadQueue tsWriteQueue (bell tsWriteQueue))

      let tsRead  = readTQueue tsReadQueue
          tsWrite = writeTQueue tsWriteQueue

      pure (TerminalSystem{..}, Private{..})

    stop :: HasLogFunc e
         => (TerminalSystem, Private) -> RIO e ()
    stop (TerminalSystem{..}, Private{..}) = do
      -- Note that we don't `cancel pReaderThread` here. This is a deliberate
      -- decision because fdRead calls into a native function which the runtime
      -- can't kill. If we were to cancel here, the internal `waitCatch` would
      -- block until the next piece of keyboard input. Since this only happens
      -- at shutdown, just leak the file descriptor.

      cancel pWriterThread
      -- take the terminal out of raw mode
      io $ setTerminalAttributes stdInput pPreviousConfiguration Immediately

    -- A list of terminal flags that we disable
    disabledFlags = [
      -- lflag
      StartStopOutput, KeyboardInterrupts, EnableEcho, EchoLF,
      ProcessInput, ExtendedFunctions,
      -- iflag
      MapCRtoLF, CheckParity, StripHighBit,
      -- cflag, todo: Terminal library missing CSIZE?
      EnableParity,
      -- oflag
      ProcessOutput
      ]

    getCap term cap =
      T.getCapability term (T.tiGetOutput1 cap) :: Maybe T.TermOutput

    vtClearScreen t  = getCap t "clear"
    vtClearToBegin t = getCap t "el"
    vtSoundBell t    = getCap t "bel"
    vtParmLeft t     = getCap t "cub1"
    vtParmRight t    = getCap t "cuf1"

    -- An async which will put into an mvar after a delay. Used to spin the
    -- spinner in writeTerminal.
    spinnerHeartBeat :: Int -> Int -> TMVar () -> RIO e ()
    spinnerHeartBeat first rest mvar = do
        threadDelay first
        loop
      where
        loop = do
          atomically $ putTMVar mvar ()
          threadDelay rest
          loop

    -- Writes data to the terminal. Both the terminal reading, normal logging,
    -- and effect handling can all emit bytes which go to the terminal.
    writeTerminal :: T.Terminal -> TQueue DrvEv -> TMVar () -> RIO e ()
    writeTerminal t q spinner = do
        currentTime <- io $ now
        loop (LineState "" 0 Nothing Nothing True 0 currentTime)
      where
        writeBlank :: LineState -> RIO e LineState
        writeBlank ls = do
            io $ T.runTermOutput t $ termText "\r\n"
            pure ls

        writeTrace :: LineState -> Text -> RIO e LineState
        writeTrace ls p = do
            io $ T.runTermOutput t $ termText "\r"
            runMaybeTermOutput t vtClearToBegin
            io $ T.runTermOutput t $ termText p
            termRefreshLine t ls

        {-
            Figure out how long to wait to show the spinner. When we
            don't have a vane name to display, we assume its a user
            action and trigger immediately. Otherwise, if we receive an
            event shortly after a previous spin, use a shorter delay to
            avoid giving the impression of a half-idle system.
        -}
        doSpin :: LineState -> Maybe Text -> RIO e LineState
        doSpin ls@LineState{..} mTxt = do
            current <- io $ now
            delay   <- pure $ case mTxt of
                Nothing -> 0
                Just _  ->
                  if (gap current lsPrevEndTime ^. microSecs) < _spin_idle_us
                  then _spin_warm_us
                  else _spin_cool_us

            spinTimer <- async $ spinnerHeartBeat delay _spin_rate_us spinner

            pure $ ls { lsSpinTimer       = Just spinTimer
                      , lsSpinCause       = mTxt
                      , lsSpinFirstRender = True
                      }

        unspin :: LineState -> RIO e LineState
        unspin ls@LineState{..} = do
              maybe (pure ()) cancel lsSpinTimer
              -- We do a final flush of the spinner mvar to ensure we don't
              -- have a lingering signal which will redisplay the spinner after
              -- we call termRefreshLine below.
              atomically $ tryTakeTMVar spinner

              -- If we ever actually ran the spinner display callback, we need
              -- to force a redisplay of the command prompt.
              ls <- if not lsSpinFirstRender
                    then termRefreshLine t ls
                    else pure ls

              endTime <- io $ now
              pure $ ls { lsSpinTimer = Nothing, lsPrevEndTime = endTime }

        execEv :: LineState -> DrvEv -> RIO e LineState
        execEv ls = \case
            DEBlits bs         -> foldM (writeBlit t) ls bs
            DETrace p          -> writeTrace ls p
            DEBlank            -> writeBlank ls
            DESpinr (Just txt) -> doSpin ls txt
            DESpinr Nothing    -> unspin ls

        spin :: LineState -> RIO e LineState
        spin ls@LineState{..} = do
            let spinner = (spinners !! lsSpinFrame) ++ case lsSpinCause of
                  Nothing  -> ""
                  Just str -> leftBracket ++ str ++ rightBracket

            io $ T.runTermOutput t $ termText spinner
            termSpinnerMoveLeft t (length spinner)

            let newFrame = (lsSpinFrame + 1) `mod` (length spinners)

            pure $ ls { lsSpinFirstRender = False
                      , lsSpinFrame       = newFrame
                      }

        loop :: LineState -> RIO e ()
        loop ls = do
            join $ atomically $ asum
                [ readTQueue q      >>= pure . (execEv ls >=> loop)
                , takeTMVar spinner >>  pure (spin ls >>= loop)
                ]

    -- Writes an individual blit to the screen
    writeBlit :: T.Terminal -> LineState -> Blit -> RIO e LineState
    writeBlit t ls = \case
      Bel () -> do
        runMaybeTermOutput t vtSoundBell
        pure ls
      Clr () -> do
        runMaybeTermOutput t vtClearScreen
        termRefreshLine t ls
      (Hop w) -> do
        termShowCursor t ls (fromIntegral w)
      (Lin c)  -> do
        ls2 <- termShowClear t ls
        termShowLine t ls2 (pack c)
      (Mor ()) -> do
        termShowMore t ls
      (Sag path noun) -> pure ls
      (Sav path atom) -> pure ls
      (Url url) -> pure ls

    -- Moves the cursor to the requested position
    termShowCursor :: T.Terminal -> LineState -> Int -> RIO e LineState
    termShowCursor t ls@LineState{..} {-line pos)-} newPos = do
      if newPos < lsCurPos then do
        replicateM_ (lsCurPos - newPos) (runMaybeTermOutput t vtParmLeft)
        pure ls { lsCurPos =  newPos }
      else if newPos > lsCurPos then do
        replicateM_ (newPos - lsCurPos) (runMaybeTermOutput t vtParmRight)
        pure ls { lsCurPos =  newPos }
      else
        pure ls

    -- Moves the cursor left without any mutation of the LineState. Used only
    -- in cursor spinning.
    termSpinnerMoveLeft :: T.Terminal -> Int -> RIO e ()
    termSpinnerMoveLeft t count =
      replicateM_ count (runMaybeTermOutput t vtParmLeft)

    -- Displays and sets the current line
    termShowLine :: T.Terminal -> LineState -> Text -> RIO e LineState
    termShowLine t ls newStr = do
      io $ T.runTermOutput t $ termText newStr
      pure ls { lsLine = newStr, lsCurPos = (length newStr) }

    termShowClear :: T.Terminal -> LineState -> RIO e LineState
    termShowClear t ls = do
      io $ T.runTermOutput t $ termText "\r"
      runMaybeTermOutput t vtClearToBegin
      pure ls { lsLine = "", lsCurPos = 0  }

    -- New Current Line
    termShowMore :: T.Terminal -> LineState -> RIO e LineState
    termShowMore t ls = do
      io $ T.runTermOutput t $ termText "\r\n"
      pure ls { lsLine = "", lsCurPos = 0  }

    -- Redraw the current LineState, maintaining the current curpos
    termRefreshLine :: T.Terminal -> LineState -> RIO e LineState
    termRefreshLine t ls = do
      let line = (lsLine ls)
          curPos = (lsCurPos ls)
      ls <- termShowClear t ls
      ls <- termShowLine t ls line
      termShowCursor t ls curPos

    -- ring my bell
    bell :: TQueue DrvEv -> RIO e ()
    bell q = atomically $ writeTQueue q $ DEBlits [Bel ()]

    -- Reads data from stdInput and emit the proper effect
    --
    -- This entire path is a divergence from how term.c does things,
    -- probably. First, the vtime is 0, not 1 in term.c. So (IIUC), we'll
    -- always have a latency of 1/10 of a second.
    --
    -- A better way to do this would be to get some sort of epoll on stdInput,
    -- since that's kinda closer to what libuv does?
    readTerminal :: forall e. HasLogFunc e
                 => TQueue Belt -> TQueue DrvEv -> (RIO e ()) -> RIO e ()
    readTerminal rq wq bell =
      rioAllocaBytes 1 $ \ buf -> loop (ReadData buf False False mempty 0)
      where
        loop :: ReadData -> RIO e ()
        loop rd@ReadData{..} = do
          -- The problem with using fdRead raw is that it will text encode
          -- things like \ESC instead of 27. That makes it broken for our
          -- purposes.
          --
          t <- io $ try (fdReadBuf stdInput rdBuf 1)
          case t of
            Left (e :: IOException) -> do
              -- Ignore EAGAINs when doing reads
              loop rd
            Right 0 -> loop rd
            Right _ -> do
              w   <- io $ peek rdBuf
              -- print ("{" ++ (show w) ++ "}")
              let c = BS.w2c w
              if rdEscape then
                if rdBracket then do
                  case c of
                    'A' -> sendBelt $ Aro U
                    'B' -> sendBelt $ Aro D
                    'C' -> sendBelt $ Aro R
                    'D' -> sendBelt $ Aro L
                    _   -> bell
                  loop rd { rdEscape = False, rdBracket = False}
                else if isAsciiLower c then do
                  sendBelt $ Met $ Cord $ pack [c]
                  loop rd { rdEscape = False }
                else if c == '.' then do
                  sendBelt $ Met $ Cord "dot"
                  loop rd { rdEscape = False }
                else if w == 8 || w == 127 then do
                  sendBelt $ Met $ Cord "bac"
                  loop rd { rdEscape = False }
                else if c == '[' || c == '0' then do
                  loop rd { rdBracket = True }
                else do
                  bell
                  loop rd { rdEscape = False }
              else if rdUTF8width /= 0 then do
                -- continue reading into the utf8 accumulation buffer
                rd@ReadData{..} <- pure rd { rdUTF8 = snoc rdUTF8 w }
                if length rdUTF8 /= rdUTF8width then loop rd
                else do
                  case BS.decode rdUTF8 of
                    Nothing ->
                      error "empty utf8 accumulation buffer"
                    Just (c, bytes) | bytes /= rdUTF8width ->
                      error "utf8 character size mismatch?!"
                    Just (c, bytes) -> sendBelt $ Txt $ Tour $ [c]
                  loop rd { rdUTF8 = mempty, rdUTF8width = 0 }
              else if w >= 32 && w < 127 then do
                sendBelt $ Txt $ Tour $ [c]
                loop rd
              else if w == 0 then do
                bell
                loop rd
              else if w == 8 || w == 127 then do
                sendBelt $ Bac ()
                loop rd
              else if w == 13 then do
                sendBelt $ Ret ()
                loop rd
              else if w == 3 then do
                -- ETX (^C)
                logDebug $ displayShow "Ctrl-c interrupt"
                atomically $ do
                  writeTQueue wq $ DETrace "interrupt\r\n"
                  writeTQueue rq $ Ctl $ Cord "c"
                loop rd
              else if w <= 26 then do
                sendBelt $ Ctl $ Cord $ pack [BS.w2c (w + 97 - 1)]
                loop rd
              else if w == 27 then do
                loop rd { rdEscape = True }
              else do
                -- start the utf8 accumulation buffer
                loop rd { rdUTF8 = singleton w,
                          rdUTF8width = if w < 224 then 2
                                        else if w < 240 then 3
                                        else 4 }

        sendBelt :: HasLogFunc e => Belt -> RIO e ()
        sendBelt b = do
          logDebug $ displayShow ("terminalBelt", b)
          atomically $ writeTQueue rq b

--------------------------------------------------------------------------------

term :: forall e. HasLogFunc e
     => TerminalSystem -> (STM ()) -> FilePath -> KingId -> QueueEv
     -> ([Ev], RAcquire e (EffCb e TermEf))
term TerminalSystem{..} shutdownSTM pierPath king enqueueEv =
    (initialEvents, runTerm)
  where
    initialEvents = [(initialBlew 80 24), initialHail]

    runTerm :: RAcquire e (EffCb e TermEf)
    runTerm = do
      tim <- mkRAcquire start stop
      pure handleEffect

    start :: RIO e (Async ())
    start = async readBelt

    stop :: Async () -> RIO e ()
    stop rb = cancel rb

    readBelt :: RIO e ()
    readBelt = forever $ do
      b <- atomically tsRead
      let blip = EvBlip $ BlipEvTerm $ TermEvBelt (UD 1, ()) $ b
      atomically $ enqueueEv $ blip

    handleEffect :: TermEf -> RIO e ()
    handleEffect = \case
      TermEfBlit _ blits -> do
        let (termBlits, fsWrites) = partition isTerminalBlit blits
        atomically $ tsWrite (DEBlits termBlits)
        for_ fsWrites handleFsWrite
      TermEfInit _ _ -> pure ()
      TermEfLogo path _ -> do
        atomically $ shutdownSTM
      TermEfMass _ _ -> pure ()

    handleFsWrite :: Blit -> RIO e ()
    handleFsWrite (Sag path noun) = performPut path (jamBS noun)
    handleFsWrite (Sav path atom) = performPut path (atom ^. atomBytes)
    handleFsWrite _               = pure ()

    performPut :: Path -> ByteString -> RIO e ()
    performPut path bs = do
      let putOutFile = pierPath </> ".urb" </> "put" </> (pathToFilePath path)
      createDirectoryIfMissing True (takeDirectory putOutFile)
      writeFile putOutFile bs