Limit embeded items

src/PostgREST/RangeQuery.hs

@@ -4,13 +4,16 @@ module PostgREST.RangeQuery (
 , rangeLimit
 , rangeOffset
 , restrictRange
+, rangeGeq
 , NonnegRange
+, limitToRange
+, toRange
 ) where
 
 
 import           Control.Applicative
 import           Network.HTTP.Types.Header
-import           PostgREST.Types           ()
+import           Data.Monoid               ((<>))
 
 import qualified Data.ByteString.Char8     as BS
 import           Data.Ranged.Boundaries
@@ -38,12 +41,13 @@ rangeParse range = do
       rangeIntersection lower upper
     Nothing -> rangeGeq 0
 
-rangeRequested :: RequestHeaders -> NonnegRange
-rangeRequested = rangeParse . fromMaybe "" . lookup hRange
+rangeRequested :: RequestHeaders -> Maybe NonnegRange
+rangeRequested headers = rangeParse <$> lookup hRange headers
 
-restrictRange :: Maybe Integer -> NonnegRange -> NonnegRange
+restrictRange :: Maybe Integer -> Maybe NonnegRange -> Maybe NonnegRange
 restrictRange Nothing r = r
-restrictRange (Just limit) r =
+restrictRange (Just limit) Nothing = Just $ rangeIntersection (rangeGeq 0) (rangeLeq (limit - 1))
+restrictRange (Just limit) (Just r) = Just $
   rangeIntersection r $
     Range BoundaryBelowAll (BoundaryAbove $ rangeOffset r + limit - 1)
 
@@ -66,3 +70,17 @@ rangeGeq n =
 rangeLeq :: Integer -> NonnegRange
 rangeLeq n =
   Range BoundaryBelowAll (BoundaryAbove n)
+
+limitToRange :: BS.ByteString -> NonnegRange
+limitToRange l = rangeParse ("0-" <> cs (show (l' - 1)))
+  where l' = fromMaybe 0 (readMaybe $ cs l)::Integer
+
+toRange :: Maybe String -> Maybe String -> Maybe NonnegRange
+toRange Nothing Nothing = Nothing
+toRange Nothing (Just o) = Just $ rangeParse $ cs $ show o' <> "-"
+  where o' = fromMaybe 0 (readMaybe $ cs o)::Integer
+toRange (Just l) Nothing = Just $ limitToRange $ cs l
+toRange (Just l) (Just o) = Just $ rangeParse $ cs $ show o' <> "-" <> show (o' + l' - 1)
+  where
+    l' = fromMaybe 0 (readMaybe $ cs l)::Integer
+    o' = fromMaybe 0 (readMaybe $ cs o)::Integer