module HBS2.Data.Log.Structured.SD where

import HBS2.Prelude.Plated
import HBS2.OrDie

import Network.ByteOrder qualified as N
import Data.ByteString.Builder qualified as B
import Data.ByteString.Lazy (ByteString)
import Data.ByteString.Lazy qualified as LBS
import Data.ByteString qualified as BS
import Data.Maybe
import Network.ByteOrder hiding (ByteString)
import Control.Monad.State

import Codec.Compression.Zstd.Streaming (Result(..))

import Control.Exception
import Lens.Micro.Platform

-- import UnliftIO

class ReadLogOpts a where

data ReadLogError = SomeReadLogError
  deriving stock (Typeable, Show)

instance Exception ReadLogError

instance ReadLogOpts ()

type NumBytes = Int

class Monad m => BytesReader m where
  noBytesLeft    :: m Bool
  readBytes      :: NumBytes -> m ByteString

  readBytesMaybe :: NumBytes -> m (Maybe ByteString)
  readBytesMaybe n = do
    bs <- readBytes n
    if LBS.length bs == fromIntegral n then pure (Just bs) else pure Nothing

newtype ConsumeLBS m a = ConsumeLBS { fromConsumeLBS :: StateT ByteString m a  }
                         deriving newtype ( Applicative
                                          , Functor
                                          , Monad
                                          , MonadState ByteString
                                          , MonadIO
                                          , MonadTrans
                                          )

readChunkThrow :: MonadIO m => Int -> ConsumeLBS m ByteString
readChunkThrow n = do
  lbs <- get
  let (this, that) = LBS.splitAt (fromIntegral n) lbs
  if LBS.length this /= fromIntegral n then
      liftIO $ throwIO SomeReadLogError
  else do
    put $! that
    pure this

readChunkSimple :: Monad m => Int -> ConsumeLBS m ByteString
readChunkSimple n = do
  lbs <- get
  let (this, that) = LBS.splitAt (fromIntegral n) lbs
  put $! that
  pure this

reminds :: Monad m => ConsumeLBS m Int
reminds = gets (fromIntegral . LBS.length)

consumed  :: Monad m => ConsumeLBS m Bool
consumed = gets LBS.null

runConsumeLBS :: Monad m => ByteString -> ConsumeLBS m a -> m a
runConsumeLBS s m  = evalStateT (fromConsumeLBS m) s

newtype ConsumeBS m a = ConsumeBS { fromConsumeBS :: StateT BS.ByteString m a  }
                        deriving newtype ( Applicative
                                         , Functor
                                         , Monad
                                         , MonadState BS.ByteString
                                         , MonadIO
                                         , MonadTrans
                                         )


instance Monad m => BytesReader (ConsumeLBS m) where
  readBytes = readChunkSimple
  noBytesLeft = consumed

instance Monad m => BytesReader (ConsumeBS m) where
  noBytesLeft = gets BS.null
  readBytes n = do
    s <- get
    let (a,b) = BS.splitAt n s
    put $! b
    pure (LBS.fromStrict a)

{- HLINT ignore "Eta reduce"-}
toSectionList :: BS.ByteString -> [BS.ByteString]
toSectionList source = go source
  where
    go bs | BS.length bs < 4 = []
          | otherwise = go1 (BS.splitAt 4 bs & over _1 (fromIntegral . N.word32))

    go1 (len,rest) | BS.length rest < len = []

    go1 (len,rest) = do
      let (sect, rest1) = BS.splitAt len rest
      sect : go rest1

validateSorted :: BS.ByteString -> Bool
validateSorted bs = do
    let sections = toSectionList bs
    let r = flip fix (Nothing, sections, 0) $ \next -> \case
              (_, [], e) -> e
              (Nothing, x:xs, e) -> next (Just x, xs, e)
              (Just v, x:_, e) | v > x -> (e+1)
              (Just _, x:xs, e)  -> next (Just x, xs, e)
    r == 0


scanBS :: Monad m => BS.ByteString -> ( BS.ByteString -> m () ) -> m ()
scanBS bs action = do
  let hsz = 4
  flip fix bs $ \next bss -> do
    if BS.length bss < hsz then pure ()
    else do
      let (ssize, rest) = BS.splitAt hsz bss
      let size =  N.word32 ssize & fromIntegral
      let (sdata, rest2) = BS.splitAt size rest
      if BS.length sdata < size  then
        pure ()
      else do
        action sdata
        next rest2

runConsumeBS :: Monad m => BS.ByteString -> ConsumeBS m a -> m a
runConsumeBS s m = evalStateT (fromConsumeBS m) s


readSections :: forall m . (MonadIO m, BytesReader m)
             => ( Int -> ByteString -> m () )
             -> m ()

readSections action = fix \next -> do
  done <- noBytesLeft
  if done then
    pure ()
  else do
    ssize <- readBytesMaybe 4
               >>= orThrow SomeReadLogError
               <&> fromIntegral . N.word32 . LBS.toStrict

    sdata <- readBytesMaybe ssize
               >>= orThrow SomeReadLogError

    action ssize sdata
    next

writeSection :: forall m . Monad m
             => ByteString
             -> ( ByteString -> m () )
             -> m ()

writeSection bs output = do
  let bssize  = bytestring32 (fromIntegral $ LBS.length bs)
  let section = B.byteString bssize <> B.lazyByteString bs
  output (B.toLazyByteString section)


writeSections :: forall m . Monad m
              => m (Maybe ByteString)
              -> ( ByteString -> m () )
              -> m ()

writeSections source sink = fix \next -> do
    source >>= maybe none (\bs -> writeSection bs sink >> next)


data CompressedStreamError =
  CompressedStreamWriteError
  deriving stock (Typeable,Show)

instance Exception CompressedStreamError

writeCompressedChunkZstd :: forall m . MonadIO m
                         => ( ByteString -> m () )
                         -> Result
                         -> Maybe ByteString
                         -> m Result

writeCompressedChunkZstd sink stream mlbs  = do
  flip fix ( LBS.toChunks lbs, stream) $ \next -> \case

    ([], r@(Done s)) -> sink (LBS.fromStrict s) >> pure r

    (_, Done{}) -> liftIO (throwIO CompressedStreamWriteError)

    (_, Error{})-> liftIO (throwIO CompressedStreamWriteError)

    (w, Produce s continue) -> do
      sink (LBS.fromStrict s)
      c <- liftIO continue
      next (w, c)

    (_, Consume consume) | isNothing mlbs -> do
      r <- liftIO (consume mempty)
      next ([], r)

    ([], r@(Consume{})) -> pure r

    (x:xs, r@(Consume consume)) -> do
      what <- liftIO (consume x)
      next (xs, what)

  where
    lbs = fromMaybe mempty mlbs


writeCompressedStreamZstd :: forall m . MonadIO m
                          => Result
                          -> m (Maybe ByteString)
                          -> ( ByteString -> m () )
                          -> m ()
writeCompressedStreamZstd stream source sink = do
  flip fix stream $ \next sn -> do
    source >>= \case
      Nothing  -> writeCompressedChunkZstd sink sn Nothing >> none
      Just lbs -> writeCompressedChunkZstd sink sn (Just lbs) >>= next


binarySearchBS :: Monad m
             => Int           -- ^ record size
             -> ( BS.ByteString -> BS.ByteString ) -- ^ key extractor
             -> BS.ByteString -- ^ key
             -> BS.ByteString -- ^ source
             -> m (Maybe Int)

binarySearchBS rs getKey s source = do
  let maxn = BS.length source `div` rs
  loop 0 maxn
  where
    loop l u | u <= l = pure Nothing
             | otherwise = do
                 let e = getKey (BS.drop ( k * rs ) source)
                 case compare e s of
                  EQ -> pure $ Just (k * rs)
                  LT -> loop (k+1) u
                  GT -> loop l k

      where k = (l + u) `div` 2