diff --git a/lib/dune b/lib/dune
index 9306f91..46c8902 100644
--- a/lib/dune
+++ b/lib/dune
@@ -1,7 +1,7 @@
 (library
  (name pgn_logic)
  (public_name pgn_to_tex)
- (libraries sedlex menhirLib)
+ (libraries sedlex menhirLib yojson)
  (modules ast parser lexer parsing latex latex_helpers pgn2tex nag)
  (preprocess
   (pps sedlex.ppx)))
diff --git a/lib/pgn2tex.ml b/lib/pgn2tex.ml
index 24dc4bc..0753f37 100644
--- a/lib/pgn2tex.ml
+++ b/lib/pgn2tex.ml
@@ -1,4 +1,17 @@
 module MoveMap = Ast.MoveMap
+open Yojson.Safe.Util
+
+let parse_diagrams_json diagrams_json_str =
+  try
+    let json = Yojson.Safe.from_string diagrams_json_str in
+    let diagrams_list = to_list json in
+    List.fold_left
+      (fun acc_map item ->
+        let ply = item |> member "ply" |> to_int in
+        let fen = item |> member "fen" |> to_string in
+        MoveMap.add ply fen acc_map)
+      MoveMap.empty diagrams_list
+  with _ -> MoveMap.empty
 
 let to_tex pgn ~diagram_data ~clock =
   let game = Parsing.parse_pgn pgn in