1 files changed, 61 insertions, 0 deletions
diff --git a/lib/common.ml b/lib/common.ml
new file mode 100755
index 0000000..ba9aee6
--- /dev/null
+++ b/lib/common.ml
@@ -0,0 +1,61 @@
+open StdLabels
+open Css.Types
+
+let location_none = Location.none
+
+(** Update the declaration list with this new property if the same property
+    name is already present.
+
+    If not return [None] *)
+let merge_declations
+  : Declaration_list.t -> Declaration_list.kind -> Declaration_list.t option
+  = fun decls1 decl2 ->
+    let declarations, loc = decls1 in
+    let updated, list' =
+      List.fold_left_map declarations
+        ~init:false
+        ~f:(fun res kind ->
+            if Comparator.declaration_kind' kind decl2 = 0 then
+              true, decl2
+            else
+              res, kind)
+    in
+    match updated with
+    | false -> None
+    | _ -> Some
+             ( list'
+             , loc )
+
+(** Add all the declarations from [decl2] into the list [decl1]
+    and return the list, and all the new declarations to add *)
+let add_all_declarations
+  : Declaration_list.t -> Declaration_list.t -> Declaration_list.t * Declaration_list.t
+  = fun decls1 (decls2, loc2) ->
+
+    let decls1, remain' = List.fold_left decls2
+        ~init:(decls1, [])
+        ~f:(fun (decls1, remain) new_declaration ->
+            match merge_declations decls1 new_declaration with
+            (* TODO : Handle empty property as None *)
+            | None -> decls1, (Some new_declaration::remain)
+            | Some decls1 -> decls1, remain
+          ) in
+    (* Remove all the unused properties *)
+    let remain' = List.filter_map ~f:(fun x -> x) remain' in
+    ( decls1
+    , (remain', loc2) )
+
+
+let update_declarations
+  : (Declaration_list.t * Location.t) -> (Declaration_list.t * Location.t) list -> (Declaration_list.t * Location.t) list
+  = fun (block, loc) existing ->
+    let remain, tl = List.fold_left
+        existing
+        ~init:(block, [])
+        ~f:(fun (block, prev) (declarations, location) ->
+
+            let update, remain = add_all_declarations declarations block in
+            remain, (update, location)::prev) in
+    match fst remain with
+    | [] -> tl
+    | other -> (((other, loc), loc)::tl)