feat: poll server data so shared pages stay near-live

Refetch the current page every 15s while the tab is visible, gated by a
pure refresh policy: edit pages, hidden or offline tabs and in-flight
navigations are left alone. Replaces refresh-on-refocus with auto-refresh.

1 files changed, 43 insertions, 0 deletions

diff --git a/src/lib/shared/refresh-policy.test.ts b/src/lib/shared/refresh-policy.test.ts
new file mode 100644
index 0000000..5cab234
--- /dev/null
+++ b/src/lib/shared/refresh-policy.test.ts
@@ -0,0 +1,43 @@
+import { describe, it, expect } from 'vitest';
+import { shouldAutoRefresh } from './refresh-policy';
+
+const idle = { visible: true, online: true, navigating: false };
+
+describe('shouldAutoRefresh', () => {
+	it('refreshes a list page when the tab is visible and idle', () => {
+		expect(shouldAutoRefresh({ routeId: '/groceries', ...idle })).toBe(true);
+		expect(shouldAutoRefresh({ routeId: '/groceries/catalog', ...idle })).toBe(
+			true,
+		);
+		expect(shouldAutoRefresh({ routeId: '/projects/[id]', ...idle })).toBe(
+			true,
+		);
+	});
+
+	it('never refreshes a page holding an in-progress edit', () => {
+		expect(shouldAutoRefresh({ routeId: '/grocery/[id]', ...idle })).toBe(
+			false,
+		);
+		expect(
+			shouldAutoRefresh({
+				routeId: '/projects/[projectId]/routine/[routineId]',
+				...idle,
+			}),
+		).toBe(false);
+		expect(shouldAutoRefresh({ routeId: '/login', ...idle })).toBe(false);
+	});
+
+	it('holds off while hidden, offline or mid-navigation', () => {
+		const routeId = '/groceries';
+		expect(shouldAutoRefresh({ routeId, ...idle, visible: false })).toBe(false);
+		expect(shouldAutoRefresh({ routeId, ...idle, online: false })).toBe(false);
+		expect(shouldAutoRefresh({ routeId, ...idle, navigating: true })).toBe(
+			false,
+		);
+	});
+
+	it('holds off when the route is not resolved yet', () => {
+		expect(shouldAutoRefresh({ routeId: null, ...idle })).toBe(false);
+		expect(shouldAutoRefresh({ routeId: undefined, ...idle })).toBe(false);
+	});
+});