From 6c31b39ddb128e87a59378628cd385bdfe6d231e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julien=20Valverd=C3=A9?= <julien.valverde@mailo.com>
Date: Tue, 31 Mar 2026 20:22:58 +0200
Subject: [PATCH] Add Form.focusChunkAt

---
 packages/effect-fc/src/Form.ts | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/packages/effect-fc/src/Form.ts b/packages/effect-fc/src/Form.ts
index b8206b6..c19f782 100644
--- a/packages/effect-fc/src/Form.ts
+++ b/packages/effect-fc/src/Form.ts
@@ -324,6 +324,32 @@ export const focusTupleAt: {
     )
 })
 
+export const focusChunkAt: {
+    <P extends readonly PropertyKey[], A, I, ER, EW>(
+        self: Form<P, Chunk.Chunk<A>, Chunk.Chunk<I>, ER, EW>,
+        index: number,
+    ): Form<readonly [...P, number], A, I, ER | Cause.NoSuchElementException, EW>
+    <P extends readonly PropertyKey[], A, I, ER, EW>(
+        index: number,
+    ): (self: Form<P, Chunk.Chunk<A>, Chunk.Chunk<I>, ER, EW>) => Form<readonly [...P, number], A, I, ER | Cause.NoSuchElementException, EW>
+} = Function.dual(2, <P extends readonly PropertyKey[], A, I, ER, EW>(
+    self: Form<P, Chunk.Chunk<A>, Chunk.Chunk<I>, ER, EW>,
+    index: number,
+): Form<readonly [...P, number], A, I, ER | Cause.NoSuchElementException, EW> => {
+    const form = self as FormImpl<P, Chunk.Chunk<A>, Chunk.Chunk<I>, ER, EW>
+    const path = [...form.path, index] as const
+
+    return new FormImpl(
+        path,
+        Subscribable.mapOptionEffect(form.value, Chunk.get(index)),
+        Lens.focusChunkAt(form.encodedValue, index),
+        Subscribable.map(form.issues, issues => filterIssuesByPath(issues, path)),
+        form.isValidating,
+        form.canSubmit,
+        form.isSubmitting,
+    )
+})
+
 
 export namespace useInput {
     export interface Options {