From 53bc4407b3f4f51d8b3316f54f018badfa5b040a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julien=20Valverd=C3=A9?= <julien.valverde@mailo.com>
Date: Wed, 5 Nov 2025 01:12:56 +0100
Subject: [PATCH] Add ErrorObserver

---
 packages/effect-fc/src/ErrorObserver.ts | 57 +++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 packages/effect-fc/src/ErrorObserver.ts

diff --git a/packages/effect-fc/src/ErrorObserver.ts b/packages/effect-fc/src/ErrorObserver.ts
new file mode 100644
index 0000000..d18748c
--- /dev/null
+++ b/packages/effect-fc/src/ErrorObserver.ts
@@ -0,0 +1,57 @@
+import { type Cause, Context, Effect, Layer, type Queue, type Scope } from "effect"
+
+
+export interface ErrorObserver<EIn, EOut> {
+    readonly "~In": EIn
+    readonly "~Out": EOut
+    readonly "~Caught": Exclude<EIn, EOut>
+
+    handle<A, E, R>(effect: Effect.Effect<A, E, R>): Effect.Effect<A, Exclude<E, Exclude<EIn, EOut>>, R>
+    readonly subscribe: Effect.Effect<Queue.Dequeue<Cause.Cause<EIn>>, never, Scope.Scope>
+}
+
+
+export namespace make {
+    export type Handler<EIn, EOut> = (
+        self: Effect.Effect<never, NoInfer<EIn>>,
+        push: {
+            failure(failure: NoInfer<EIn>): Effect.Effect<never>
+            defect(defect: unknown): Effect.Effect<never>
+        },
+    ) => Effect.Effect<EOut>
+}
+
+export const make = <EIn = never>() => <EOut>(
+    f: make.Handler<NoInfer<EIn>, EOut>
+): Effect.Effect<ErrorObserver<EIn, EOut>> =>
+
+
+export const ErrorObserver: Context.Tag<
+    ErrorObserver<unknown, unknown>,
+    ErrorObserver<unknown, unknown>
+> = Context.GenericTag("@effect-fc/ErrorObserver/ErrorObserver")
+
+export namespace Service {
+    export interface Result<Self, Id extends string, EIn, EOut>
+    extends Context.TagClass<Self, Id, ErrorObserver<EIn, EOut>> {
+        readonly Default: Layer.Layer<Self>
+    }
+}
+
+export const Service = <Self, EIn>() => (
+    <const Id extends string, EOut>(
+        id: Id,
+        f: (
+            self: Effect.Effect<never, NoInfer<EIn>>,
+            actions: {
+                failure(failure: NoInfer<EIn>): Effect.Effect<never>
+                defect(defect: unknown): Effect.Effect<never>
+            },
+        ) => Effect.Effect<EOut>,
+    ): Service.Result<Self, Id, EIn, EOut> => Layer.effect(
+        ErrorObserver as Context.Tag<ErrorObserver<EIn, EOut>, ErrorObserver<EIn, EOut>>,
+        Effect.gen(function*() {
+
+        },
+    ))
+)