module Lifx.Lan (
    sendMessage,
    Message (..),
    HSBK (..),
    Duration (..),
    Lifx,
    runLifx,
    LifxT (..),
    runLifxT,
    MonadLifx (..),

    -- * Low-level
    encodeMessage,
    Header (..),
) where

import Control.Monad
import Control.Monad.Reader
import Control.Monad.State
import Data.Binary
import Data.Binary.Put
import Data.Bits
import Data.ByteString.Lazy qualified as BL
import GHC.Generics (Generic)
import Network.Socket
import Network.Socket.ByteString
import System.Random

{- Core -}

lifxPort :: PortNumber
lifxPort = 56700

sendMessage :: MonadLifx m => HostAddress -> Message -> m ()
sendMessage lightAddr msg = do
    sock <- getSocket
    source <- getSource
    sequenceCounter <- getCounter
    incrementCounter
    void . liftIO $
        sendTo
            sock
            (BL.toStrict $ encodeMessage False sequenceCounter source msg)
            (SockAddrInet lifxPort lightAddr)

data HSBK = HSBK
    { hue :: Word16
    , saturation :: Word16
    , brightness :: Word16
    , kelvin :: Word16
    }
    deriving (Eq, Ord, Show, Generic)
newtype Duration = Duration Word32
    deriving (Eq, Ord, Show, Generic)

-- | https://lan.developer.lifx.com/docs/changing-a-device
data Message
    = SetPower Bool
    | SetColor HSBK Duration
    | SetLightPower Bool Duration

{- Monad -}

type Lifx = LifxT IO
newtype LifxT m a = LifxT {unLifxT :: StateT Word8 (ReaderT (Socket, Word32) m) a}
    deriving newtype (Functor, Applicative, Monad, MonadIO, MonadReader (Socket, Word32), MonadState Word8)

runLifx :: Lifx a -> IO a
runLifx = runLifxT
runLifxT :: MonadIO m => LifxT m a -> m a
runLifxT (LifxT x) = do
    sock <- liftIO $ socket AF_INET Datagram defaultProtocol
    liftIO . bind sock $ SockAddrInet defaultPort 0
    source <- randomIO
    runReaderT (evalStateT x 0) (sock, source)

class MonadIO m => MonadLifx m where
    getSocket :: m Socket
    getSource :: m Word32
    incrementCounter :: m ()
    getCounter :: m Word8
instance MonadIO m => MonadLifx (LifxT m) where
    getSocket = asks fst
    getSource = asks snd
    incrementCounter = modify succ'
    getCounter = gets id
instance MonadLifx m => MonadLifx (StateT s m) where
    getSocket = lift getSocket
    getSource = lift getSource
    incrementCounter = lift incrementCounter
    getCounter = lift getCounter
instance MonadLifx m => MonadLifx (ReaderT e m) where
    getSocket = lift getSocket
    getSource = lift getSource
    incrementCounter = lift incrementCounter
    getCounter = lift getCounter

{- Low level -}

encodeMessage :: Bool -> Word8 -> Word32 -> Message -> BL.ByteString
encodeMessage ackRequired sequenceCounter source msg =
    runPut $ putHeader (messageHeader ackRequired sequenceCounter source msg) >> putMessagePayload msg

-- | https://lan.developer.lifx.com/docs/encoding-a-packet
data Header = Header
    { size :: Word16
    , protocol :: Word16
    , addressable :: Bool
    , tagged :: Bool
    , origin :: Word8
    , source :: Word32
    , target :: Word64
    , resRequired :: Bool
    , ackRequired :: Bool
    , sequenceCounter :: Word8
    , packetType :: Word16
    }

putHeader :: Header -> Put
putHeader Header{..} = do
    putWord16le size
    putWord16le $
        protocol
            .|. bitIf addressable 12
            .|. bitIf tagged 13
            .|. bitIf (testBit origin 0) 14
            .|. bitIf (testBit origin 1) 15
    putWord32le source
    putWord64be target
    replicateM_ 6 $ putWord8 0
    putWord8 $
        zeroBits
            .|. bitIf resRequired 0
            .|. bitIf ackRequired 1
    putWord8 sequenceCounter
    replicateM_ 8 $ putWord8 0
    putWord16le packetType
    replicateM_ 2 $ putWord8 0
  where
    bitIf b n = if b then bit n else zeroBits

messageHeader :: Bool -> Word8 -> Word32 -> Message -> Header
messageHeader ackRequired sequenceCounter source = \case
    SetPower{} ->
        Header
            { size = headerSize + 2
            , packetType = 21
            , ..
            }
    SetColor{} ->
        Header
            { size = headerSize + 13
            , packetType = 102
            , ..
            }
    SetLightPower{} ->
        Header
            { size = headerSize + 6
            , packetType = 117
            , ..
            }
  where
    target = 0
    headerSize = 36
    protocol = 1024
    tagged = True
    addressable = True
    origin = 0
    resRequired = False

putMessagePayload :: Message -> Put
putMessagePayload = \case
    SetPower b ->
        putWord16le if b then maxBound else minBound
    SetColor HSBK{..} (Duration d) -> do
        putWord8 0
        putWord16le hue
        putWord16le saturation
        putWord16le brightness
        putWord16le kelvin
        putWord32le d
    SetLightPower b (Duration d) -> do
        putWord16le if b then maxBound else minBound
        putWord32le d

{- Util -}

-- | Safe, wraparound variant of 'succ'.
succ' :: (Eq a, Bounded a, Enum a) => a -> a
succ' e
    | e == maxBound = minBound
    | otherwise = succ e