refactor(unsaved): extract createUnsavedWarning hook and UnsavedWarningBanner

Move the identical isDirty / beforeNavigate / discard pattern out of the
three admin detail pages (groups, tags, users) into a reusable
createUnsavedWarning() hook and a UnsavedWarningBanner presentational
component.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/UnsavedWarningBanner.svelte

@@ -0,0 +1,22 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+
+interface Props {
+	onDiscard: () => void;
+}
+
+let { onDiscard }: Props = $props();
+</script>
+
+<div
+	class="mb-5 flex items-center justify-between rounded border border-amber-200 bg-amber-50 p-3 text-sm text-amber-800 dark:border-amber-800 dark:bg-amber-950/40 dark:text-amber-300"
+>
+	<span>{m.admin_unsaved_warning()}</span>
+	<button
+		type="button"
+		onclick={onDiscard}
+		class="ml-4 shrink-0 font-sans text-xs font-bold tracking-widest text-amber-800 uppercase hover:text-amber-900 dark:text-amber-300"
+	>
+		{m.person_discard_changes()}
+	</button>
+</div>

frontend/src/lib/hooks/__tests__/useUnsavedWarning.svelte.test.ts

@@ -0,0 +1,95 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// Capture the beforeNavigate callback so tests can simulate navigation events
+let registeredBeforeNavigate:
+	| ((nav: { cancel: () => void; to: { url: { href: string } } | null }) => void)
+	| null = null;
+
+const mockGoto = vi.fn();
+
+vi.mock('$app/navigation', () => ({
+	beforeNavigate: vi.fn((fn: typeof registeredBeforeNavigate) => {
+		registeredBeforeNavigate = fn;
+	}),
+	goto: mockGoto
+}));
+
+const { createUnsavedWarning } = await import('../useUnsavedWarning.svelte');
+
+function simulateNavigate(href: string | null = '/somewhere') {
+	const cancel = vi.fn();
+	registeredBeforeNavigate?.({
+		cancel,
+		to: href ? { url: { href } } : null
+	});
+	return cancel;
+}
+
+beforeEach(() => {
+	registeredBeforeNavigate = null;
+	mockGoto.mockClear();
+});
+
+describe('createUnsavedWarning', () => {
+	it('isDirty starts false', () => {
+		const w = createUnsavedWarning();
+		expect(w.isDirty).toBe(false);
+	});
+
+	it('markDirty sets isDirty to true', () => {
+		const w = createUnsavedWarning();
+		w.markDirty();
+		expect(w.isDirty).toBe(true);
+	});
+
+	it('markDirty hides any existing warning banner', () => {
+		const w = createUnsavedWarning();
+		// Simulate a navigation event that showed the banner
+		w.markDirty();
+		simulateNavigate();
+		expect(w.showUnsavedWarning).toBe(true);
+		// Typing again should hide the banner (form input re-triggers markDirty)
+		w.markDirty();
+		expect(w.showUnsavedWarning).toBe(false);
+	});
+
+	it('beforeNavigate cancels and shows banner when dirty', () => {
+		const w = createUnsavedWarning();
+		w.markDirty();
+		const cancel = simulateNavigate('/admin/users');
+		expect(cancel).toHaveBeenCalled();
+		expect(w.showUnsavedWarning).toBe(true);
+	});
+
+	it('beforeNavigate stores the target URL', () => {
+		const w = createUnsavedWarning();
+		w.markDirty();
+		simulateNavigate('/admin/users');
+		expect(w.discardTarget).toBe('/admin/users');
+	});
+
+	it('beforeNavigate does not cancel when not dirty', () => {
+		createUnsavedWarning();
+		const cancel = simulateNavigate('/admin/users');
+		expect(cancel).not.toHaveBeenCalled();
+	});
+
+	it('discard resets state and navigates to target', () => {
+		const w = createUnsavedWarning();
+		w.markDirty();
+		simulateNavigate('/admin/tags');
+		w.discard();
+		expect(w.isDirty).toBe(false);
+		expect(w.showUnsavedWarning).toBe(false);
+		expect(mockGoto).toHaveBeenCalledWith('/admin/tags');
+	});
+
+	it('clearOnSuccess resets isDirty and warning', () => {
+		const w = createUnsavedWarning();
+		w.markDirty();
+		simulateNavigate('/somewhere');
+		w.clearOnSuccess();
+		expect(w.isDirty).toBe(false);
+		expect(w.showUnsavedWarning).toBe(false);
+	});
+});

frontend/src/lib/hooks/useUnsavedWarning.svelte.ts

@@ -0,0 +1,46 @@
+import { beforeNavigate, goto } from '$app/navigation';
+
+export function createUnsavedWarning() {
+	let isDirty = $state(false);
+	let showUnsavedWarning = $state(false);
+	let discardTarget: string | null = $state(null);
+
+	beforeNavigate(({ cancel, to }) => {
+		if (isDirty) {
+			cancel();
+			showUnsavedWarning = true;
+			discardTarget = to?.url.href ?? null;
+		}
+	});
+
+	function markDirty() {
+		isDirty = true;
+		showUnsavedWarning = false;
+	}
+
+	function discard() {
+		isDirty = false;
+		showUnsavedWarning = false;
+		if (discardTarget) goto(discardTarget);
+	}
+
+	function clearOnSuccess() {
+		isDirty = false;
+		showUnsavedWarning = false;
+	}
+
+	return {
+		get isDirty() {
+			return isDirty;
+		},
+		get showUnsavedWarning() {
+			return showUnsavedWarning;
+		},
+		get discardTarget() {
+			return discardTarget;
+		},
+		markDirty,
+		discard,
+		clearOnSuccess
+	};
+}

frontend/src/routes/admin/groups/[id]/+page.svelte

@@ -1,16 +1,15 @@
 <script lang="ts">
 import { enhance } from '$app/forms';
-import { beforeNavigate, goto } from '$app/navigation';
 import { m } from '$lib/paraglide/messages.js';
 import { getConfirmService } from '$lib/services/confirm.svelte.js';
+import { createUnsavedWarning } from '$lib/hooks/useUnsavedWarning.svelte';
+import UnsavedWarningBanner from '$lib/components/UnsavedWarningBanner.svelte';
 
 let { data, form } = $props();
 
 const { confirm } = getConfirmService();
+const unsaved = createUnsavedWarning();
 
-let isDirty = $state(false);
-let showUnsavedWarning = $state(false);
-let discardTarget: string | null = $state(null);
 let deleteFormEl = $state<HTMLFormElement | null>(null);
 
 async function handleDelete() {
@@ -21,19 +20,8 @@ async function handleDelete() {
 	if (confirmed) deleteFormEl!.requestSubmit();
 }
 
-beforeNavigate(({ cancel, to }) => {
-	if (isDirty) {
-		cancel();
-		showUnsavedWarning = true;
-		discardTarget = to?.url.href ?? null;
-	}
-});
-
 $effect(() => {
-	if (form?.success) {
-		isDirty = false;
-		showUnsavedWarning = false;
-	}
+	if (form?.success) unsaved.clearOnSuccess();
 });
 
 const STANDARD_PERMISSIONS = $derived([
@@ -84,23 +72,8 @@ const ADMIN_PERMISSIONS = $derived([
 
 	<!-- Scrollable body -->
 	<div class="flex-1 overflow-y-auto px-5 py-5">
-		{#if showUnsavedWarning}
-			<div
-				class="mb-5 flex items-center justify-between rounded border border-amber-200 bg-amber-50 p-3 text-sm text-amber-800 dark:border-amber-800 dark:bg-amber-950/40 dark:text-amber-300"
-			>
-				<span>{m.admin_unsaved_warning()}</span>
-				<button
-					type="button"
-					onclick={() => {
-						isDirty = false;
-						showUnsavedWarning = false;
-						if (discardTarget) goto(discardTarget);
-					}}
-					class="ml-4 shrink-0 font-sans text-xs font-bold tracking-widest text-amber-800 uppercase hover:text-amber-900 dark:text-amber-300"
-				>
-					{m.person_discard_changes()}
-				</button>
-			</div>
+		{#if unsaved.showUnsavedWarning}
+			<UnsavedWarningBanner onDiscard={unsaved.discard} />
 		{/if}
 		{#if form?.success}
 			<div
@@ -122,10 +95,7 @@ const ADMIN_PERMISSIONS = $derived([
 			method="POST"
 			action="?/update"
 			use:enhance
-			oninput={() => {
-				isDirty = true;
-				showUnsavedWarning = false;
-			}}
+			oninput={unsaved.markDirty}
 		>
 			<!-- Group name card -->
 			<div class="mb-5 rounded-sm border border-line bg-surface p-5 shadow-sm">

frontend/src/routes/admin/tags/[id]/+page.svelte

@@ -1,30 +1,18 @@
 <script lang="ts">
 import { enhance } from '$app/forms';
-import { beforeNavigate, goto } from '$app/navigation';
 import { m } from '$lib/paraglide/messages.js';
+import { createUnsavedWarning } from '$lib/hooks/useUnsavedWarning.svelte';
+import UnsavedWarningBanner from '$lib/components/UnsavedWarningBanner.svelte';
 
 let { data, form } = $props();
 
 let deleteConfirmName = $state('');
 const deleteEnabled = $derived(deleteConfirmName === data.tag.name);
 
-let isDirty = $state(false);
-let showUnsavedWarning = $state(false);
-let discardTarget: string | null = $state(null);
-
-beforeNavigate(({ cancel, to }) => {
-	if (isDirty) {
-		cancel();
-		showUnsavedWarning = true;
-		discardTarget = to?.url.href ?? null;
-	}
-});
+const unsaved = createUnsavedWarning();
 
 $effect(() => {
-	if (form?.success) {
-		isDirty = false;
-		showUnsavedWarning = false;
-	}
+	if (form?.success) unsaved.clearOnSuccess();
 });
 </script>
 
@@ -53,23 +41,8 @@ $effect(() => {
 
 	<!-- Scrollable body -->
 	<div class="flex-1 overflow-y-auto px-5 py-5">
-		{#if showUnsavedWarning}
-			<div
-				class="mb-5 flex items-center justify-between rounded border border-amber-200 bg-amber-50 p-3 text-sm text-amber-800 dark:border-amber-800 dark:bg-amber-950/40 dark:text-amber-300"
-			>
-				<span>{m.admin_unsaved_warning()}</span>
-				<button
-					type="button"
-					onclick={() => {
-						isDirty = false;
-						showUnsavedWarning = false;
-						if (discardTarget) goto(discardTarget);
-					}}
-					class="ml-4 shrink-0 font-sans text-xs font-bold tracking-widest text-amber-800 uppercase hover:text-amber-900 dark:text-amber-300"
-				>
-					{m.person_discard_changes()}
-				</button>
-			</div>
+		{#if unsaved.showUnsavedWarning}
+			<UnsavedWarningBanner onDiscard={unsaved.discard} />
 		{/if}
 		{#if form?.success}
 			<div class="mb-5 rounded border border-green-200 bg-green-50 p-3 text-sm text-green-700">
@@ -88,10 +61,7 @@ $effect(() => {
 			method="POST"
 			action="?/update"
 			use:enhance
-			oninput={() => {
-				isDirty = true;
-				showUnsavedWarning = false;
-			}}
+			oninput={unsaved.markDirty}
 			class="mb-5"
 		>
 			<div class="rounded-sm border border-line bg-surface p-5 shadow-sm">

frontend/src/routes/admin/users/[id]/+page.svelte

@@ -1,21 +1,20 @@
 <script lang="ts">
 import { enhance } from '$app/forms';
-import { beforeNavigate, goto } from '$app/navigation';
 import { m } from '$lib/paraglide/messages.js';
 import { getConfirmService } from '$lib/services/confirm.svelte.js';
 import UserProfileSection from '$lib/components/user/UserProfileSection.svelte';
 import UserGroupsSection from '$lib/components/user/UserGroupsSection.svelte';
 import UserPasswordSection from '$lib/components/user/UserPasswordSection.svelte';
+import { createUnsavedWarning } from '$lib/hooks/useUnsavedWarning.svelte';
+import UnsavedWarningBanner from '$lib/components/UnsavedWarningBanner.svelte';
 
 let { data, form } = $props();
 
 const { confirm } = getConfirmService();
+const unsaved = createUnsavedWarning();
 
 const selectedGroupIds = $derived(data.editUser.groups?.map((g: { id: string }) => g.id) ?? []);
 
-let isDirty = $state(false);
-let showUnsavedWarning = $state(false);
-let discardTarget: string | null = $state(null);
 let deleteFormEl = $state<HTMLFormElement | null>(null);
 
 async function handleDelete() {
@@ -26,19 +25,8 @@ async function handleDelete() {
 	if (confirmed) deleteFormEl!.requestSubmit();
 }
 
-beforeNavigate(({ cancel, to }) => {
-	if (isDirty) {
-		cancel();
-		showUnsavedWarning = true;
-		discardTarget = to?.url.href ?? null;
-	}
-});
-
 $effect(() => {
-	if (form?.success) {
-		isDirty = false;
-		showUnsavedWarning = false;
-	}
+	if (form?.success) unsaved.clearOnSuccess();
 });
 </script>
 
@@ -76,23 +64,8 @@ $effect(() => {
 
 	<!-- Scrollable body -->
 	<div class="flex-1 overflow-y-auto px-5 py-5">
-		{#if showUnsavedWarning}
-			<div
-				class="mb-5 flex items-center justify-between rounded border border-amber-200 bg-amber-50 p-3 text-sm text-amber-800 dark:border-amber-800 dark:bg-amber-950/40 dark:text-amber-300"
-			>
-				<span>{m.admin_unsaved_warning()}</span>
-				<button
-					type="button"
-					onclick={() => {
-						isDirty = false;
-						showUnsavedWarning = false;
-						if (discardTarget) goto(discardTarget);
-					}}
-					class="ml-4 shrink-0 font-sans text-xs font-bold tracking-widest text-amber-800 uppercase hover:text-amber-900 dark:text-amber-300"
-				>
-					{m.person_discard_changes()}
-				</button>
-			</div>
+		{#if unsaved.showUnsavedWarning}
+			<UnsavedWarningBanner onDiscard={unsaved.discard} />
 		{/if}
 		{#if form?.success}
 			<div class="mb-5 rounded border border-green-200 bg-green-50 p-3 text-sm text-green-700">
@@ -109,10 +82,7 @@ $effect(() => {
 			id="edit-user-form"
 			method="POST"
 			use:enhance
-			oninput={() => {
-				isDirty = true;
-				showUnsavedWarning = false;
-			}}
+			oninput={unsaved.markDirty}
 			class="space-y-5"
 		>
 			<!-- Profile card -->