refactor `Join`

1 files changed, 24 insertions, 23 deletions

diff --git a/app/Main.hs b/app/Main.hs
index dfee5e0..5ce4dd0 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -40,7 +40,8 @@ main = do
           ]
       )
       "c"
-      [ LeftJoin
+      [ JoinClause
+          JoinLeft
           "j"
           [ Eq (Qualified "j" "id") (Qualified "c" "j_id")
           ]
@@ -56,7 +57,8 @@ main = do
           ]
       )
       "c"
-      [ RightJoin
+      [ JoinClause
+          JoinRight
           "j"
           [ Eq (Qualified "j" "id") (Qualified "c" "j_id")
           ]
@@ -72,7 +74,8 @@ main = do
           ]
       )
       "c"
-      [ FullJoin
+      [ JoinClause
+          JoinFull
           "j"
           [ Eq (Qualified "j" "id") (Qualified "c" "j_id")
           ]
@@ -80,7 +83,7 @@ main = do
       []
 
 data Query
-  = Select FieldSelector Collection [Join FilePath] WhereClauses
+  = Select FieldSelector Collection (JoinClauses FilePath) WhereClauses
   deriving (Show)
 
 data FieldSelector
@@ -95,10 +98,16 @@ data Field
 
 type Collection = FilePath
 
-data Join a
-  = LeftJoin a WhereClauses
-  | RightJoin a WhereClauses
-  | FullJoin a WhereClauses
+type JoinClauses a = [JoinClause a]
+
+data JoinClause a
+  = JoinClause JoinType a WhereClauses
+  deriving (Show)
+
+data JoinType
+  = JoinLeft
+  | JoinRight
+  | JoinFull
   deriving (Show)
 
 type WhereClauses = [WhereClause]
@@ -122,17 +131,9 @@ query (Select fs c js ws) = do
     mapM (fmap (Record c) . decodeFile . (c </>)) =<< ls c
   js' <-
     mapM
-      ( \j ->
-          case j of
-            LeftJoin c ws ->
-              fmap (\j' -> LeftJoin (map (Record c) j') ws) . mapM (decodeFile . (c </>))
-                =<< ls c
-            RightJoin c ws ->
-              fmap (\j' -> RightJoin (map (Record c) j') ws) . mapM (decodeFile . (c </>))
-                =<< ls c
-            FullJoin c ws ->
-              fmap (\j' -> FullJoin (map (Record c) j') ws) . mapM (decodeFile . (c </>))
-                =<< ls c
+      ( \(JoinClause t c ws) ->
+          fmap (\j' -> JoinClause t (map (Record c) j') ws) . mapM (decodeFile . (c </>))
+            =<< ls c
       )
       js
   pure $ map (select fs) $ where_ ws $ combine c' js'
@@ -142,11 +143,11 @@ query (Select fs c js ws) = do
         <$> S.withStore "." "HEAD" do
           S.listDirectory c
 
-combine :: [Record J.Value] -> [Join [Record J.Value]] -> [[Record J.Value]]
+combine :: [Record J.Value] -> JoinClauses [Record J.Value] -> [[Record J.Value]]
 combine vs js = combine' (map (: []) vs) js
   where
     combine' vss [] = vss
-    combine' vss (LeftJoin js ws : jss) =
+    combine' vss (JoinClause JoinLeft js ws : jss) =
       combine'
         ( concatMap
             ( \vs -> case filter (satisfies ws) $ map (\j -> vs ++ [j]) js of
@@ -156,7 +157,7 @@ combine vs js = combine' (map (: []) vs) js
             vss
         )
         jss
-    combine' vss (RightJoin js ws : jss) =
+    combine' vss (JoinClause JoinRight js ws : jss) =
       combine'
         ( concatMap
             ( \j -> case filter (satisfies ws) $ map (\vs -> vs ++ [j]) vss of
@@ -166,7 +167,7 @@ combine vs js = combine' (map (: []) vs) js
             js
         )
         jss
-    combine' vss (FullJoin js ws : jss) =
+    combine' vss (JoinClause JoinFull js ws : jss) =
       combine'
         ( concatMap
             ( \vs -> case filter (satisfies ws) $ map (\j -> vs ++ [j]) js of