mapAccumL -bytestring +text

mapAccumL :: (a -> Char -> (a, Char)) -> a -> Text -> (a, Text)
text Data.Text, text Data.Text.Lazy
O(n) Like a combination of map and foldl'. Applies a function to each element of a Text, passing an accumulating parameter from left to right, and returns a final Text. Performs replacement on invalid scalar values.