From 213fed9f2da164f83498c904a2ec8140c75ebfcd Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Fri, 2 May 2025 10:30:58 -0400
Subject: [PATCH] wip: eio

---
 dune-project             | 12 ++++++++++++
 src/eio/dune             |  5 +++++
 src/eio/moonpool_eio.ml  | 24 ++++++++++++++++++++++++
 src/eio/moonpool_eio.mli |  4 ++++
 4 files changed, 45 insertions(+)
 create mode 100644 src/eio/dune
 create mode 100644 src/eio/moonpool_eio.ml
 create mode 100644 src/eio/moonpool_eio.mli

diff --git a/dune-project b/dune-project
index 7f1de178..6656281c 100644
--- a/dune-project
+++ b/dune-project
@@ -37,6 +37,18 @@
  (tags
   (thread pool domain futures fork-join)))
 
+(package
+  (name moonpool-eio)
+  (synopsis "Compatibility layer between moonpool and Eio")
+  (allow_empty)  ; on < 5.0
+  (depends
+    (moonpool (= :version))
+    (ocaml (>= 5.0))
+    eio
+    (trace :with-test)
+    (trace-tef :with-test)
+    (odoc :with-doc)))
+
 (package
   (name moonpool-lwt)
   (synopsis "Event loop for moonpool based on Lwt-engine (experimental)")
diff --git a/src/eio/dune b/src/eio/dune
new file mode 100644
index 00000000..839c7953
--- /dev/null
+++ b/src/eio/dune
@@ -0,0 +1,5 @@
+(library
+ (name moonpool_eio)
+ (public_name moonpool-eio)
+ (synopsis "compatibility layer between moonpool and eio")
+ (libraries moonpool eio))
diff --git a/src/eio/moonpool_eio.ml b/src/eio/moonpool_eio.ml
new file mode 100644
index 00000000..7ca64d4b
--- /dev/null
+++ b/src/eio/moonpool_eio.ml
@@ -0,0 +1,24 @@
+let fut_of_moonpool (fut : 'a Moonpool.Fut.t) : 'a Eio.Promise.or_exn =
+  match Moonpool.Fut.peek fut with
+  | Some (Ok r) -> Eio.Promise.create_resolved @@ Ok r
+  | Some (Error (exn, _bt)) ->
+    let prom, resolver = Eio.Promise.create () in
+    Eio.Promise.resolve_error resolver exn;
+    prom
+  | None ->
+    let prom, resolver = Eio.Promise.create () in
+    Moonpool.Fut.on_result fut (function
+      | Ok r -> Eio.Promise.resolve_ok resolver r
+      | Error (exn, _) -> Eio.Promise.resolve_error resolver exn);
+    prom
+
+let await_moonpool (fut : 'a Moonpool.Fut.t) : 'a =
+  match Moonpool.Fut.peek fut with
+  | Some (Ok r) -> r
+  | Some (Error (exn, bt)) -> Printexc.raise_with_backtrace exn bt
+  | None ->
+    let prom, resolver = Eio.Promise.create () in
+    Moonpool.Fut.on_result fut (function
+      | Ok r -> Eio.Promise.resolve_ok resolver r
+      | Error (exn, _) -> Eio.Promise.resolve_error resolver exn);
+    Eio.Promise.await_exn prom
diff --git a/src/eio/moonpool_eio.mli b/src/eio/moonpool_eio.mli
new file mode 100644
index 00000000..56ab6459
--- /dev/null
+++ b/src/eio/moonpool_eio.mli
@@ -0,0 +1,4 @@
+val fut_of_moonpool : 'a Moonpool.Fut.t -> 'a Eio.Promise.or_exn
+
+val await_moonpool : 'a Moonpool.Fut.t -> 'a
+(** Await a moonpool future *)