Differential D1672 Diff 6000 swh/web/tests/resources/contents/code/extensions/test.hs

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swh/web/tests/resources/contents/code/extensions/test.hs

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				{-\|
				Module : PostgREST.RangeQuery
				Description : Logic regarding the `Range` header and `limit`, `offset` querystring arguments.
				-}
				module PostgREST.RangeQuery (
				rangeParse
				, rangeRequested
				, rangeLimit
				, rangeOffset
				, restrictRange
				, rangeGeq
				, allRange
				, NonnegRange
				) where

				import qualified Data.ByteString.Char8 as BS

				import Data.List (lookup)
				import Text.Regex.TDFA ((=~))

				import Control.Applicative
				import Data.Ranged.Boundaries
				import Data.Ranged.Ranges
				import Network.HTTP.Types.Header

				import Protolude

				type NonnegRange = Range Integer

				rangeParse :: BS.ByteString -> NonnegRange
				rangeParse range = do
				let rangeRegex = "^([0-9]+)-([0-9]*)$" :: BS.ByteString

				case listToMaybe (range =~ rangeRegex :: [[BS.ByteString]]) of
				Just parsedRange ->
				let [_, mLower, mUpper] = readMaybe . toS <$> parsedRange
				lower = maybe emptyRange rangeGeq mLower
				upper = maybe allRange rangeLeq mUpper in
				rangeIntersection lower upper
				Nothing -> allRange

				rangeRequested :: RequestHeaders -> NonnegRange
				rangeRequested headers = maybe allRange rangeParse $ lookup hRange headers

				restrictRange :: Maybe Integer -> NonnegRange -> NonnegRange
				restrictRange Nothing r = r
				restrictRange (Just limit) r =
				rangeIntersection r $
				Range BoundaryBelowAll (BoundaryAbove $ rangeOffset r + limit - 1)

				rangeLimit :: NonnegRange -> Maybe Integer
				rangeLimit range =
				case [rangeLower range, rangeUpper range] of
				[BoundaryBelow lower, BoundaryAbove upper] -> Just (1 + upper - lower)
				_ -> Nothing

				rangeOffset :: NonnegRange -> Integer
				rangeOffset range =
				case rangeLower range of
				BoundaryBelow lower -> lower
				_ -> panic "range without lower bound" -- should never happen

				rangeGeq :: Integer -> NonnegRange
				rangeGeq n =
				Range (BoundaryBelow n) BoundaryAboveAll

				allRange :: NonnegRange
				allRange = rangeGeq 0

				rangeLeq :: Integer -> NonnegRange
				rangeLeq n =
				Range BoundaryBelowAll (BoundaryAbove n)