add `LIMIT`, `ORDER BY` clausesmain

1 files changed, 36 insertions, 6 deletions

diff --git a/src/Store/Query.hs b/src/Store/Query.hs
index 091aae7..4c0f829 100644
--- a/src/Store/Query.hs
+++ b/src/Store/Query.hs
@@ -16,6 +16,7 @@ import Data.Map qualified as M
 import Data.Maybe (fromMaybe)
 import Data.Text qualified as T
 import Data.Vector qualified as V
+import GHC.Generics (Generic)
 import Store.Exception (DecodeException (DecodeException), MissingFileName (MissingFileName))
 import Store.Query.Parser ()
 import Store.Query.Printer ()
@@ -24,7 +25,17 @@ import Store.Query.Type
 import Store.Store qualified as S
 import System.FilePath ((</>))
 
-query :: Query -> S.StoreM [J.Value]
+data Paginated = Paginated
+  { count :: Int,
+    data_ :: [J.Value]
+  }
+  deriving (Show, Generic)
+
+instance J.ToJSON Paginated
+
+instance J.FromJSON Paginated
+
+query :: Query -> S.StoreM J.Value
 query (Delete c w) = do
   c' <-
     mapM (\fn -> fmap ((fn,) . fromValue c) . decodeFile c $ fn)
@@ -33,7 +44,7 @@ query (Delete c w) = do
   lift $ print fps
   mapM_ S.deleteFile (map (c </>) fps)
   S.commit
-  pure []
+  pure (J.toJSON ([] @()))
 query (Insert vs c) = do
   let vs' = map (\v -> ((c, fileName v), v)) vs
 
@@ -43,8 +54,8 @@ query (Insert vs c) = do
           _ -> throw (MissingFileName v)
   mapM_ (\((c, fn), v) -> encodeFile c fn v) vs'
   S.commit
-  pure []
-query (Select fs c js es w) = do
+  pure (J.toJSON ([] @()))
+query (Select fs c js es w l o) = do
   c' <-
     mapM (\fn -> fromValue c <$> decodeFile c fn)
       =<< S.listFiles c
@@ -64,7 +75,18 @@ query (Select fs c js es w) = do
             =<< S.listFiles c
       )
       es
-  pure $ map (Store.Query.select fs) $ where_ w $ embeds es' $ joins js' c'
+  let rs =
+        map (Store.Query.select fs)
+          . where_ w
+          . embeds es'
+          . joins js'
+          $ c'
+      rs' =
+        case l >> o >> pure () of
+          (Just _) ->
+            J.toJSON (Paginated (length rs) . applyLimit l . applyOffset o $ rs)
+          _ -> J.toJSON rs
+  pure rs'
 query (Update c v w) = do
   c' <-
     mapM (\fn -> fmap (((c, fn),) . fromValue c) . decodeFile c $ fn)
@@ -76,7 +98,15 @@ query (Update c v w) = do
     )
     c''
   S.commit
-  pure []
+  pure (J.toJSON ([] @()))
+
+applyLimit :: Maybe LimitClause -> [a] -> [a]
+applyLimit Nothing = id
+applyLimit (Just (Limit n)) = take n
+
+applyOffset :: Maybe OffsetClause -> [a] -> [a]
+applyOffset Nothing = id
+applyOffset (Just (Offset n)) = drop n
 
 embeds ::
   EmbedClauses (Record [J.Value]) ->