implemented encodeRawRows

src/Data/CSV/Sip.hs

@@ -32,6 +32,9 @@ module Data.CSV.Sip (
   slurpLabelledCSV,
   slurpRawLabelledCSV,
   -- * Conduits
+  -- ** Encoding
+  encodeRawRows,
+  -- ** Decoding
   labelFields,
   decodeRows,
   decodeRawRows,
@@ -94,6 +97,17 @@ slurpRawLabelledCSV
 slurpRawLabelledCSV file = runConduit $
   sourceFile file .| decodeRawRows .| labelFields .|consume
 
+-- | encode raw CSV stream row by row, each element in the list read
+-- represents a field, with the entire list representing a row
+encodeRawRows :: Monad m => ConduitT [BS.ByteString] BS.ByteString m ()
+encodeRawRows = await >>= \case
+
+  Just fs-> do
+    encodeFields fs
+    encodeRawRows
+
+  Nothing -> return ()
+
 -- | read a CSV stream, using the first row as a header containing
 -- field labels
 labelFields :: (Monad m, Ord a) => ConduitT [a] (M.Map a a) m ()
@@ -144,6 +158,16 @@ newDecodeState = DecodeState
 
 -- Conduits
 
+encodeFields
+  :: Monad m
+  => [BS.ByteString]
+  -> ConduitT [BS.ByteString] BS.ByteString m ()
+encodeFields []     = yield "\r\n"
+encodeFields [f]    = yield $ escapeField f `BS.append` "\r\n"
+encodeFields (f:fs) = do
+  yield $ escapeField f `BS.append` ","
+  encodeFields fs
+
 labelLoop :: (Monad m, Ord a) => [a] -> ConduitT [a] (M.Map a a) m ()
 labelLoop headers = await >>= \case
   Just values -> do
@@ -270,4 +294,19 @@ dropField s = s
 setQuoted :: Modifier
 setQuoted s = s { isQuoted = True }
 
+-- Helpers
+escapeField :: BS.ByteString -> BS.ByteString
+escapeField field = let
+  bytes = BS.unpack field
+  in BS.concat
+    [ "\""
+    , BS.pack $ escapeLoop bytes
+    , "\""
+    ]
+
+escapeLoop :: [Word8] -> [Word8]
+escapeLoop []        = []
+escapeLoop (0x22:bs) = [0x22, 0x22] ++ escapeLoop bs -- escape quote
+escapeLoop (b:bs)    = b : escapeLoop bs
+
 --jl