115 lines
4.5 KiB
Haskell
115 lines
4.5 KiB
Haskell
{-# LANGUAGE RankNTypes #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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{-# LANGUAGE BangPatterns #-}
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module Colonnade.Decoding where
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import Colonnade.Internal (EitherWrap(..))
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import Colonnade.Types
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import Data.Functor.Contravariant
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import Data.Vector (Vector)
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import qualified Data.Vector as Vector
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-- | Converts the content type of a 'Decoding'. The @'Contravariant' f@
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-- constraint means that @f@ can be 'Headless' but not 'Headed'.
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contramapContent :: forall c1 c2 f a. Contravariant f => (c2 -> c1) -> Decoding f c1 a -> Decoding f c2 a
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contramapContent f = go
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where
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go :: forall b. Decoding f c1 b -> Decoding f c2 b
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go (DecodingPure x) = DecodingPure x
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go (DecodingAp h decode apNext) =
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DecodingAp (contramap f h) (decode . f) (go apNext)
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headless :: (content -> Either String a) -> Decoding Headless content a
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headless f = DecodingAp Headless f (DecodingPure id)
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headed :: content -> (content -> Either String a) -> Decoding Headed content a
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headed h f = DecodingAp (Headed h) f (DecodingPure id)
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indexed :: Int -> (content -> Either String a) -> Decoding (Indexed Headless) content a
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indexed ix f = DecodingAp (Indexed ix Headless) f (DecodingPure id)
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maxIndex :: forall f c a. Decoding (Indexed f) c a -> Int
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maxIndex = go 0 where
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go :: forall b. Int -> Decoding (Indexed f) c b -> Int
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go !ix (DecodingPure _) = ix
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go !ix1 (DecodingAp (Indexed ix2 _) decode apNext) =
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go (max ix1 ix2) apNext
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-- | This function uses 'unsafeIndex' to access
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-- elements of the 'Vector'.
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uncheckedRunWithRow ::
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Int
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-> Decoding (Indexed f) content a
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-> Vector content
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-> Either (DecodingRowError f content) a
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uncheckedRunWithRow i d v = mapLeft (DecodingRowError i . RowErrorDecode) (uncheckedRun d v)
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-- | This function does not check to make sure that the indicies in
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-- the 'Decoding' are in the 'Vector'.
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uncheckedRun :: forall content a f.
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Decoding (Indexed f) content a
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-> Vector content
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-> Either (DecodingCellErrors f content) a
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uncheckedRun dc v = getEitherWrap (go dc)
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where
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go :: forall b.
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Decoding (Indexed f) content b
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-> EitherWrap (DecodingCellErrors f content) b
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go (DecodingPure b) = EitherWrap (Right b)
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go (DecodingAp ixed@(Indexed ix h) decode apNext) =
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let rnext = go apNext
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content = Vector.unsafeIndex v ix
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rcurrent = mapLeft (DecodingCellErrors . Vector.singleton . DecodingCellError content ixed) (decode content)
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in rnext <*> (EitherWrap rcurrent)
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headlessToIndexed :: forall c a.
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Decoding Headless c a -> Decoding (Indexed Headless) c a
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headlessToIndexed = go 0 where
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go :: forall b. Int -> Decoding Headless c b -> Decoding (Indexed Headless) c b
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go !ix (DecodingPure a) = DecodingPure a
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go !ix (DecodingAp Headless decode apNext) =
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DecodingAp (Indexed ix Headless) decode (go (ix + 1) apNext)
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length :: forall f c a. Decoding f c a -> Int
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length = go 0 where
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go :: forall b. Int -> Decoding f c b -> Int
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go !a (DecodingPure _) = a
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go !a (DecodingAp _ _ apNext) = go (a + 1) apNext
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-- | Maps over a 'Decoding' that expects headers, converting these
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-- expected headers into the indices of the columns that they
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-- correspond to.
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headedToIndexed :: forall content a. Eq content
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=> Vector content -- ^ Headers in the source document
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-> Decoding Headed content a -- ^ Decoding that contains expected headers
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-> Either (HeadingErrors content) (Decoding (Indexed Headed) content a)
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headedToIndexed v = getEitherWrap . go
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where
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go :: forall b. Eq content
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=> Decoding Headed content b
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-> EitherWrap (HeadingErrors content) (Decoding (Indexed Headed) content b)
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go (DecodingPure b) = EitherWrap (Right (DecodingPure b))
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go (DecodingAp hd@(Headed h) decode apNext) =
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let rnext = go apNext
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ixs = Vector.elemIndices h v
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ixsLen = Vector.length ixs
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rcurrent
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| ixsLen == 1 = Right (Vector.unsafeIndex ixs 0)
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| ixsLen == 0 = Left (HeadingErrors (Vector.singleton h) Vector.empty)
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| otherwise = Left (HeadingErrors Vector.empty (Vector.singleton (h,ixsLen)))
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in (\ix ap -> DecodingAp (Indexed ix hd) decode ap)
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<$> EitherWrap rcurrent
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<*> rnext
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eitherMonoidAp :: Monoid a => Either a (b -> c) -> Either a b -> Either a c
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eitherMonoidAp = go where
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go (Left a1) (Left a2) = Left (mappend a1 a2)
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go (Left a1) (Right _) = Left a1
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go (Right _) (Left a2) = Left a2
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go (Right f) (Right b) = Right (f b)
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mapLeft :: (a -> b) -> Either a c -> Either b c
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mapLeft _ (Right a) = Right a
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mapLeft f (Left a) = Left (f a)
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