From cc783c157f31e7e713c8b83be67449b1859dac27 Mon Sep 17 00:00:00 2001
From: Marc Coquand <marc@mccd.space>
Date: Wed, 20 Dec 2023 20:43:25 -0600
Subject: Initial commit

---
 lib/activitypub/common.ml | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 lib/activitypub/common.ml

(limited to 'lib/activitypub/common.ml')

diff --git a/lib/activitypub/common.ml b/lib/activitypub/common.ml
new file mode 100644
index 0000000..59c7099
--- /dev/null
+++ b/lib/activitypub/common.ml
@@ -0,0 +1,47 @@
+module D = Decoders_yojson.Safe.Decode
+
+let timestamp =
+  let open D in
+  let* time = string in
+  match Ptime.of_rfc3339 time |> Ptime.rfc3339_error_to_msg with
+  | Ok (t, _, _) -> succeed t
+  | Error `Msg err -> fail err
+
+let singleton_or_list dec =
+  D.(one_of ["singleton", (dec >|= fun v -> [v]);
+             "list", list dec;
+             "null", null >|= fun () -> []])  
+
+let lossy_list_of dec =
+  let open D in
+  list (one_of ["known", (dec >|= fun v -> `Value v); "unknown", value >|= fun v -> `Raw v])
+
+
+let constant ?msg target =
+  let open D in
+  let* str = string in
+  if String.equal str target
+  then succeed ()
+  else match msg with
+    | None -> fail (Printf.sprintf "expected %s received %s" target str)
+    | Some msg -> fail (Printf.sprintf msg str)
+
+let field_or_default field' decoder default =
+  let open D in
+  let+ field = field_opt field' decoder in
+  Option.value ~default field
+
+let list_ignoring_unknown ty =
+  let open D in
+  list (maybe ty) >|= fun v -> List.filter_map Fun.id v
+
+let items obj =
+  let open D in
+  one_of [
+    ("ordered items",
+     let* items = field "orderedItems" (list obj) in
+     succeed (true, items));
+    "items",
+    let* items = field "items" (list obj) in
+    succeed (false, items)
+  ]
-- 
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