module HBS2.Actors.ChunkWriter
  ( ChunkWriter
  , ChunkId
  , newChunkWriterIO
  , runChunkWriter
  , stopChunkWriter
  , newBlock
  , delBlock
  , commitBlock
  , writeChunk
  , getHash
  ) where

import HBS2.Prelude
import HBS2.Actors
import HBS2.Hash
import HBS2.Storage
import HBS2.Defaults

import Control.Exception
import Data.ByteString.Lazy (ByteString)
import Data.ByteString.Lazy qualified as B
-- import Data.Cache (Cache)
-- import Data.Cache qualified as Cache
import Data.Hashable (hash)
import Data.Maybe
import Data.Word
import Prettyprinter
import System.Directory
import System.FilePath
import System.IO.Error
import System.IO
import System.IO.Temp

import Control.Concurrent.Async

import Control.Concurrent.STM
import Control.Concurrent.STM.TBQueue qualified as Q

-- TODO: cache file handles

newtype ChunkId = ChunkId FilePath
                  deriving newtype (IsString)
                  deriving stock (Eq,Ord,Show)

data ChunkWriter h m = forall a . ( MonadIO m
                                  , Storage a h ByteString m
                                  , Block ByteString ~ ByteString
                                  ) =>
  ChunkWriter
  { pipeline :: Pipeline m ()
  , dir      :: FilePath
  , storage  :: a
  }



runChunkWriter :: MonadIO m => ChunkWriter h m -> m ()
runChunkWriter w = do
  liftIO $ createDirectoryIfMissing True ( dir w )
  runPipeline (pipeline w)

stopChunkWriter :: MonadIO m => ChunkWriter h m -> m ()
stopChunkWriter w = stopPipeline ( pipeline w )

newChunkWriterIO :: forall h a m . ( Key h ~ Hash h, h ~ HbSync
                                   , Storage a h ByteString m
                                   , Block ByteString ~ ByteString
                                   , MonadIO m
                                   )
                 => a
                 -> Maybe FilePath
                 -> m (ChunkWriter h m)

newChunkWriterIO s tmp = do
  pip <- newPipeline defChunkWriterQ

  def  <- liftIO $ getXdgDirectory XdgData (defStorePath  </> "temp-chunks")
  let d  = fromMaybe def tmp

  pure $
    ChunkWriter
    { pipeline = pip
    , dir = d
    , storage  = s
    }

makeFileName :: (Hashable salt, Pretty (Hash h)) => ChunkWriter h m -> salt -> Hash h -> FilePath
makeFileName w salt h = dir w </> suff
  where
    suff = show $ pretty (fromIntegral (hash salt) :: Word32) <> "@" <> pretty h

-- TODO: check uniqueness
newBlock :: ( MonadIO m
            , Hashable salt
            , Pretty (Hash h)
            )
         => ChunkWriter h m
         -> salt
         -> Hash h
         -> Size -> m ()

newBlock w salt h size = liftIO do
  withBinaryFile fn ReadWriteMode (`hSetFileSize` fromIntegral size)
  where
    fn = makeFileName w salt h

delBlock :: (Hashable salt, MonadIO m, Pretty (Hash h))
         => ChunkWriter h m -> salt -> Hash h -> m ()

delBlock w salt h = liftIO do
  void $ tryJust (guard . isDoesNotExistError) (removeFile fn)
  where
    fn = makeFileName w salt h

writeChunk :: (Hashable salt, MonadIO m, Pretty (Hash h))
           => ChunkWriter h m
           -> salt
           -> Hash h
           -> Offset
           -> ByteString -> m ()

writeChunk w salt h o bs = addJob (pipeline w) $ liftIO do
  withBinaryFile fn ReadWriteMode $ \fh -> do
    hSeek fh AbsoluteSeek (fromIntegral o)
    B.hPutStr fh bs
    hFlush fh

  where
    fn = makeFileName w salt h

-- Blocking!
-- we need to write last chunk before this will happen
-- FIXME: incremental calculation,
--        streaming, blah-blah
getHash :: forall salt h m .
           ( Hashable salt
           , Hashed h ByteString
           , MonadIO m
           , Block ByteString ~ ByteString
           , Pretty (Hash h)
           )
         => ChunkWriter h m
         -> salt
         -> Hash h
         -> m (Hash h)

getHash w salt h = liftIO do

  q <- Q.newTBQueueIO 1

  addJob (pipeline w) $ liftIO do
    h1 <- hashObject @h <$> B.readFile fn
    atomically $ Q.writeTBQueue q h1

  atomically $ Q.readTBQueue q

  where
    fn = makeFileName w salt h


commitBlock :: forall salt h m .
               ( Hashable salt
               , Hashed h ByteString
               , Block ByteString ~ ByteString
               , MonadIO m
               , Pretty (Hash h)
               )
            => ChunkWriter h m
            -> salt
            -> Hash h
            -> m ()

commitBlock w@(ChunkWriter {storage = stor}) salt h = do
  q <- liftIO $ Q.newTBQueueIO 1

  addJob (pipeline w)  (liftIO $ B.readFile fn >>= atomically . Q.writeTBQueue q)

  s <- liftIO $ atomically $ Q.readTBQueue q

  void $ putBlock stor s

  delBlock w salt h

  where
    fn = makeFileName w salt h