Move sources into src

src/RangeQuery.hs

@@ -0,0 +1,52 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module RangeQuery where
+
+import Control.Applicative
+import Network.HTTP.Types.Header
+
+import Data.Ranged.Boundaries
+import Data.Ranged.Ranges
+
+import qualified Data.ByteString.Char8 as BS
+import Text.Regex.TDFA ((=~))
+import Text.Read (readMaybe)
+
+import Data.Maybe (fromMaybe, listToMaybe)
+
+type NonnegRange = Range Int
+
+rangeGeq :: Int -> NonnegRange
+rangeGeq n =
+  Range (BoundaryBelow n) BoundaryAboveAll
+
+rangeLeq :: Int -> NonnegRange
+rangeLeq n =
+  Range BoundaryBelowAll (BoundaryAbove n)
+
+parseRange :: String -> Maybe NonnegRange
+parseRange range = do
+  let rangeRegex = "^([0-9]+)-([0-9]*)$" :: String
+
+  parsedRange <- listToMaybe (range =~ rangeRegex :: [[String]])
+
+  let [_, from, to] = readMaybe <$> parsedRange
+  let lower = fromMaybe emptyRange   (rangeGeq <$> from)
+  let upper = fromMaybe (rangeGeq 0) (rangeLeq <$> to)
+
+  return $ rangeIntersection lower upper
+
+requestedRange :: RequestHeaders -> Maybe NonnegRange
+requestedRange hdrs = parseRange =<< BS.unpack <$> lookup hRange hdrs
+
+limit :: NonnegRange -> Maybe Int
+limit range =
+  case [rangeLower range, rangeUpper range]
+    of [BoundaryBelow from, BoundaryAbove to] -> Just (1 + to - from)
+       _ -> Nothing
+
+offset :: NonnegRange -> Int
+offset range =
+  case rangeLower range
+    of BoundaryBelow from -> from
+       _ -> 0 -- should never happen