csv-sip/src/Data/CSV/Slurp.hs

{-|

Module      : Data.CSV.Slurp
Description : works with CSV files
Copyright   : (C) Jonathan Lamothe
License     : GPL-3.0-or-later
Maintainer  : jonathan@jlamothe.net
Stability   : experimental
Portability : POSIX

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.

-}

{-# LANGUAGE OverloadedStrings #-}

module Data.CSV.Slurp (
  decodeRows,
  decodeRawRows,
  decodeUTF8,
  toBytes,
) where

import Conduit (ConduitT, mapC, (.|))
import Control.Monad.Trans.State (StateT, evalStateT)
import qualified Data.ByteString as BS
import Data.Maybe (fromMaybe)
import qualified Data.Text as T
import Data.Text.Encoding (decodeUtf8')
import Data.Word (Word8)

-- | decode the rows from a stream of ByteStrings
decodeRows :: Monad m => ConduitT BS.ByteString [T.Text] m ()
decodeRows = decodeRawRows .| mapC (map $ fromMaybe "" . decodeUTF8)

-- | decode the rows returning raw ByteStrings instead of text
decodeRawRows :: Monad m => ConduitT BS.ByteString [BS.ByteString] m ()
decodeRawRows = toBytes .| evalStateT decodeLoop newDecodeState

-- | decode a raw ByteString into Text (if possible)
decodeUTF8 :: BS.ByteString -> Maybe T.Text
decodeUTF8 bs = case decodeUtf8' bs of
  Left _    -> Nothing
  Right txt -> Just txt

-- | convert a stream to ByteStrings to a string of bytes
toBytes :: Monad m => ConduitT BS.ByteString Word8 m ()
toBytes = return ()

data DecodeState = DecodeState
  { isQuoted  :: Bool
  , collected :: BS.ByteString
  } deriving (Eq, Show)

newDecodeState :: DecodeState
newDecodeState = DecodeState
  { isQuoted  = False
  , collected = ""
  }

decodeLoop
  :: Monad m
  => StateT DecodeState (ConduitT Word8 [BS.ByteString] m) ()
decodeLoop = return ()

--jl