implemented labelFields

src/Data/CSV/Sip.hs

@@ -26,6 +26,7 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 {-# LANGUAGE LambdaCase, OverloadedStrings #-}
 
 module Data.CSV.Sip (
+  labelFields,
   decodeRows,
   decodeRawRows,
   decodeUTF8,
@@ -37,11 +38,18 @@ import Control.Monad (unless)
 import Control.Monad.Trans.Class (lift)
 import Control.Monad.Trans.State (StateT, evalStateT, get, gets, modify)
 import qualified Data.ByteString as BS
+import qualified Data.Map as M
 import Data.Maybe (fromMaybe)
 import qualified Data.Text as T
 import Data.Text.Encoding (decodeUtf8')
 import Data.Word (Word8)
 
+-- | 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 ()
+labelFields = await >>= \case
+  Just headers -> labelLoop headers
+  Nothing      -> return ()
+
 -- | decode the rows from a stream of ByteStrings
 decodeRows :: Monad m => ConduitT BS.ByteString [T.Text] m ()
 decodeRows = decodeRawRows .| mapC (map $ fromMaybe "" . decodeUTF8)
@@ -83,6 +91,15 @@ newDecodeState = DecodeState
   , collected = ""
   }
 
+-- Conduits
+
+labelLoop :: (Monad m, Ord a) => [a] -> ConduitT [a] (M.Map a a) m ()
+labelLoop headers = await >>= \case
+  Just values -> do
+    yield $ M.fromList $ zip headers values
+    labelLoop headers
+  Nothing     -> return ()
+
 -- Decoders
 
 decodeLoop :: Monad m => Decoder m