Zstd.hs

module Resource.Compressed.Zstd where

import RIO

import RIO.FilePath (takeExtension)
import RIO.ByteString qualified as ByteString

import Codec.Compression.Zstd qualified as Zstd

data CompressedError
  = EmptyFile FilePath
  | ZstdError Text
  deriving (Eq, Show)

instance Exception CompressedError

fromFileWith :: MonadIO m => (ByteString -> m b) -> (FilePath -> m b) -> FilePath -> m b
fromFileWith withBS withFilePath filePath
  | elem (takeExtension filePath) compressedExts =
      loadCompressed withBS filePath
  | otherwise =
      withFilePath filePath

loadCompressed :: MonadIO m => (ByteString -> m b) -> FilePath -> m b
loadCompressed withBS filePath = do
  yeet'd <- ByteString.readFile filePath
  case Zstd.decompress yeet'd of
    Zstd.Skip ->
      throwIO $ EmptyFile filePath
    Zstd.Error str ->
      throwIO $ ZstdError (fromString str)
    Zstd.Decompress buf ->
      withBS buf

compressedExts :: [FilePath]
compressedExts =
  [ ".zst"
  , ".zstd"
  ]