Accept range headers

TODO: response headers and proper codes

PgQuery.hs

@@ -7,6 +7,7 @@ import Data.Maybe (fromMaybe)
 import Data.List (intercalate)
 import Data.Monoid ((<>))
 
+import qualified RangeQuery as R
 import qualified Data.Text as T
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.ByteString.Char8 as BS
@@ -16,20 +17,24 @@ import Database.HDBC.PostgreSQL
 
 import Network.HTTP.Types.URI
 
-selectWhere :: T.Text -> T.Text -> Query -> Connection -> IO BL.ByteString
-selectWhere ver table qq conn = do
+selectWhere :: T.Text -> T.Text -> Query -> Maybe R.NonnegRange -> Connection -> IO BL.ByteString
+selectWhere ver table qq range conn = do
   s <- selectSql
   w <- whereClause conn qq
   r <- quickQuery conn (BS.unpack $ s <> w) []
+
   return $ case r of
                 [[json]] -> fromSql json
                 _        -> "" :: BL.ByteString
 
   where
+    limit = fromMaybe "ALL" $ show <$> (R.limit =<< range)
+    offset = fromMaybe 0 (R.offset <$> range)
     selectSql = pgFormat conn
           "select array_to_json(array_agg(row_to_json(t)))\
-          \  from (select * from %I.%I) t"
-        [toSql ver, toSql table]
+          \  from (select * from %I.%I LIMIT %s OFFSET %s) t"
+        [toSql ver, toSql table, toSql limit, toSql offset]
+
 
 whereClause :: Connection -> Query -> IO BS.ByteString
 whereClause _    [] = return ""
@@ -41,7 +46,7 @@ whereClause conn qs =
     clause = BS.intercalate " and " <$> preds
 
     preds :: IO [BS.ByteString]
-    preds = sequence $ map (wherePred conn) qs
+    preds = mapM (wherePred conn) qs
 
 
 wherePred :: Connection -> QueryItem -> IO BS.ByteString