{-# LANGUAGE DeriveTraversable   #-}
{-# LANGUAGE RecordWildCards     #-}
{-# LANGUAGE MultiWayIf          #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE BangPatterns        #-}
module System.FTDI.MPSSE
    ( Command
    , run
    , Failure(..)

      -- * Clock divisor
    , setClockDivisor

      -- ** FT232H divide-by-5
    , enableClkDivBy5
    , disableClkDivBy5

    , enable3PhaseClocking
    , disable3PhaseClocking

      -- * Loopback
    , enableLoopback
    , disableLoopback

      -- * Data transfer
    , BitOrder(..)
    , ClockEdge(..)
    , flush

      -- ** Pausing
    , waitOnHigh
    , waitOnLow
      -- ** Byte-wise
    , readBytes
    , writeBytes
    , readWriteBytes

      -- * GPIO
    , Gpios(..)
    , allInputs
    , Direction(..)
    , GpioBank(..)
    , setGpioDirValue
    , getGpioValue
    ) where

import Data.Bits
import Data.Word
import Numeric (showHex)

import qualified Data.ByteString as BS
import qualified Data.ByteString.Lazy as BSL
import qualified Data.ByteString.Builder as BSB

import Control.Concurrent.Async
import Control.Monad (void)

import qualified System.FTDI as FTDI
import System.FTDI (InterfaceHandle)
import System.IO

debug :: Bool
debug = False

debugLog :: String -> IO ()
debugLog
  | debug = hPutStrLn stderr
  | otherwise = const $ return ()

-- Useful for debugging
showBS :: BS.ByteString -> String
showBS = foldr (\n rest -> showHex n . showChar ' ' $ rest) "" . BS.unpack

data Command a = Command { command :: BSB.Builder
                         , expectedBytes :: !Int
                         , parseBytes :: BS.ByteString -> a
                         }

instance Functor Command where
    fmap f (Command a b c) = Command a b (f . c)
    {-# INLINE fmap #-}

instance Applicative Command where
    pure x = Command mempty 0 (const x)
    {-# INLINE pure #-}
    Command a b c <*> Command a' b' c' =
        Command (a <> a') (b + b') parse
      where
        parse bs =
            let (bs1, bs2) = BS.splitAt b bs
            in c bs1 (c' bs2)
    {-# INLINE (<*>) #-}

opCode :: Word8 -> Command ()
opCode = byte
{-# INLINE opCode #-}

byte :: Word8 -> Command ()
byte o = void $ transfer (BSB.word8 o) 0
{-# INLINE byte #-}

word16 :: Word16 -> Command ()
word16 o = void $ transfer (BSB.word16LE o) 0
{-# INLINE word16 #-}

transfer :: BSB.Builder -> Int -> Command BS.ByteString
transfer b n = Command { command = b
                       , expectedBytes = n
                       , parseBytes = id }
{-# INLINE transfer #-}

writeByteString :: BS.ByteString -> Command ()
writeByteString bs = void $ transfer (BSB.byteString bs) 0
{-# INLINE writeByteString #-}

readN :: Int -> Command BS.ByteString
readN = transfer mempty
{-# INLINE readN #-}

-------------------------------------------------------------------------------
-- Interpreter
-------------------------------------------------------------------------------

data Failure = WriteTimedOut BS.ByteString Int
               -- ^ content to be written and number of bytes actually written.
             | ReadTimedOut BS.ByteString Int BS.ByteString
               -- ^ data written, expected returned bytes, and data actually read.
             | ReadTooLong Int BS.ByteString
               -- ^ bytes expected and content actually read.
             | BadStatus BS.ByteString

instance Show Failure where
    show (WriteTimedOut write written) =
        unlines [ "Write timed out:"
                , "  Wrote " <> show written <> " of " <> show (BS.length write) <> ": " <> showBS write
                ]
    show (ReadTimedOut written expected readBS) =
        unlines [ "Read timed out:"
                , "  Wrote " <> show (BS.length written) <> ": " <> showBS written
                , "  Expected to read " <> show expected
                , "  Actually read " <> show (BS.length readBS) <> ": " <> showBS readBS
                ]
    show (ReadTooLong expected readBS) =
        unlines [ "Read too long:"
                , "  Expected to read " <> show expected
                , "  Actually read " <> show (BS.length readBS) <> ": " <> showBS readBS
                ]
    show (BadStatus status) =
        unlines [ "Bad status"
                , "  Status: " <> showBS status
                ]

-- | Assumes that the interface has already been placed in 'BitMode_MPSSE'
-- using 'setBitMode'.
run :: forall a. InterfaceHandle -> Command a -> IO (Either Failure a)
run ifHnd (Command cmd n parse) = do
    let cmd' = BSL.toStrict $ BSB.toLazyByteString cmd
    debugLog $ "W ("++show n++"): " ++ showBS cmd'
    writer <- async $ FTDI.writeBulk ifHnd cmd'
    link writer
    let readLoop :: Int -> BS.ByteString -> IO (Either Failure a)
        readLoop iters acc
          | remain < 0  = return $ Left $ ReadTooLong n acc
          | remain == 0 = return $ Right $ parse acc
          | otherwise = do
              (resp, _readStatus) <- FTDI.readBulk ifHnd (remain+2)
              debugLog $ "R " ++ show (BS.length acc) ++ "/" ++ show n ++ ": " ++ showBS resp
              let acc' = acc <> BS.drop 2 resp
                  statusOnly = BS.length resp == 2
                  iters' = if statusOnly then iters + 1 else iters
              if | BS.take 2 resp == "\xfa"  -> return $ Left $ BadStatus resp
                 | iters == 10               -> return $ Left $ ReadTimedOut cmd' n acc
                 | otherwise                 -> readLoop iters' acc'
          where remain = n - BS.length acc

    resp <- readLoop 0 mempty
    (written, _writeStatus) <- wait writer
    return $ if written /= BS.length cmd'
      then Left $ WriteTimedOut cmd' written
      else resp

{-# INLINE run #-}

-------------------------------------------------------------------------------
-- Clocking
-------------------------------------------------------------------------------

setClockDivisor :: Word16 -> Command ()
setClockDivisor n = opCode 0x86 *> word16 n
{-# INLINE setClockDivisor #-}

-- | The FT232H, FT2232H, and FT4232H can achieve higher data rates if the
-- clock divider is disabled.
disableClkDivBy5 :: Command ()
disableClkDivBy5 = opCode 0x8a

-- | Enable clock divide by 5 to allow for backward compatibility with FT2232D.
enableClkDivBy5 :: Command ()
enableClkDivBy5 = opCode 0x8b

-- | Enables 3 phase data clocking.
-- Used by I2C interfaces to allow data on both clock edges.
enable3PhaseClocking :: Command ()
enable3PhaseClocking = opCode 0x8c

-- | Disables 3 phase data clocking.
disable3PhaseClocking :: Command ()
disable3PhaseClocking = opCode 0x8d

-------------------------------------------------------------------------------
-- Loopback
-------------------------------------------------------------------------------

enableLoopback :: Command ()
enableLoopback = opCode 0x84
{-# INLINE enableLoopback #-}

disableLoopback :: Command ()
disableLoopback = opCode 0x85
{-# INLINE disableLoopback #-}

-------------------------------------------------------------------------------
-- GPIO
-------------------------------------------------------------------------------

data Gpios a = Gpios { gpio0 :: a  -- ^ BankL: TXD, clock
                     , gpio1 :: a  -- ^ BankL: RXD, TDI, MOSI
                     , gpio2 :: a  -- ^ BankL: RTS#, TDO, MISO
                     , gpio3 :: a  -- ^ BankL: CTS#, TMS, CS
                     , gpio4 :: a
                     , gpio5 :: a
                     , gpio6 :: a
                     , gpio7 :: a
                     }
             deriving (Functor, Foldable, Traversable)

data Direction i o = Input i | Output o

data GpioBank = BankL | BankH

allInputs :: Gpios (Direction () Bool)
allInputs = Gpios i i i i i i i i
  where i = Input ()

gpioBits :: Gpios Bool -> Word8
gpioBits Gpios{..} =
    b 0 gpio0 .|.
    b 1 gpio1 .|.
    b 2 gpio2 .|.
    b 3 gpio3 .|.
    b 4 gpio4 .|.
    b 5 gpio5 .|.
    b 6 gpio6 .|.
    b 7 gpio7
  where b n True  = bit n
        b _ False = 0

-- | Set the direction and logic state of the pins
setGpioDirValue :: GpioBank -> Gpios (Direction () Bool) -> Command ()
setGpioDirValue bank vals = opCode o *> byte valueByte *> byte dirByte
  where o = case bank of
              BankL -> 0x80
              BankH -> 0x82
        !dirByte = gpioBits $ fmap f vals
          where f (Output _) = True
                f _          = False
        !valueByte = gpioBits $ fmap f vals
          where f (Output True) = True
                f _             = False

-- | Read the current state of the pins in the bank and send back 1 byte
getGpioValue :: GpioBank -> Command BS.ByteString
getGpioValue BankL = opCode 0x81 *> readN 1
getGpioValue BankH = opCode 0x83 *> readN 1

-------------------------------------------------------------------------------
-- Transfers
-------------------------------------------------------------------------------

-- | This will make the chip flush its buffer back to the PC.
flush :: Command ()
flush = opCode 0x87

waitOnHigh :: Command ()
waitOnHigh = opCode 0x88

waitOnLow :: Command ()
waitOnLow = opCode 0x89

data BitOrder = MsbFirst | LsbFirst

data ClockEdge = Rising | Falling

otherEdge :: ClockEdge -> ClockEdge
otherEdge Rising  = Falling
otherEdge Falling = Rising

bitOrderBit :: BitOrder -> Word8
bitOrderBit MsbFirst = 0x0
bitOrderBit LsbFirst = 0x8

outEdgeBit :: ClockEdge -> Word8
outEdgeBit Rising  = 0x0
outEdgeBit Falling = 0x1

inEdgeBit :: ClockEdge -> Word8
inEdgeBit Rising  = 0x0
inEdgeBit Falling = 0x4

writeBytes :: ClockEdge -> BitOrder -> BS.ByteString -> Command ()
writeBytes edge order bs
  | BS.null bs = error "writeBytes: too short"
  | BS.length bs > 0x10000 = error "writeBytes: too long"
  | otherwise =
    opCode o *> word16 (fromIntegral $ BS.length bs - 1) *> writeByteString bs
  where
    o = 0x10 .|. bitOrderBit order .|. outEdgeBit edge
{-# INLINE writeBytes #-}

readBytes :: ClockEdge -> BitOrder -> Int -> Command BS.ByteString
readBytes edge order n
  | n == 0 = error "readBytes: too short"
  | n > 0x10000 = error "readBytes: too long"
  | otherwise =
    opCode o
    *> word16 (fromIntegral $ n - 1)
    *> readN (fromIntegral n)
  where
    o = 0x20 .|. bitOrderBit order .|. inEdgeBit edge
{-# INLINE readBytes #-}

readWriteBytes :: ClockEdge  -- ^ which edge to clock *out* data on
               -> BitOrder -> BS.ByteString -> Command BS.ByteString
readWriteBytes outEdge order bs
  | BS.null bs = error "readWriteBytes: too short"
  | BS.length bs > 0x10000 = error "readWriteBytes: too long"
  | otherwise =
    opCode o
    *> word16 (fromIntegral $ BS.length bs - 1)
    *> transfer (BSB.byteString bs) (BS.length bs)
  where
    o = 0x30 .|. bitOrderBit order .|. inEdgeBit (otherEdge outEdge) .|. outEdgeBit outEdge
{-# INLINE readWriteBytes #-}