Add automatic background refresh

app/src/lib/auto-refresh.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, it } from 'vitest';
+import { AUTO_REFRESH_IDLE_MS, AUTO_REFRESH_REPEAT_MS, shouldAutoRefresh } from './auto-refresh';
+
+const idleState = {
+  now: AUTO_REFRESH_REPEAT_MS,
+  lastInteractionAt: 0,
+  lastRefreshAt: 0,
+  connected: true,
+  busy: false,
+  editing: false,
+  dragging: false,
+  visible: true
+};
+
+describe('automatic refresh scheduling', () => {
+  it('refreshes after the user has been idle long enough', () => {
+    expect(shouldAutoRefresh(idleState)).toBe(true);
+  });
+
+  it('waits for ten seconds of inactivity', () => {
+    expect(shouldAutoRefresh({ ...idleState, lastInteractionAt: idleState.now - AUTO_REFRESH_IDLE_MS + 1 })).toBe(false);
+  });
+
+  it('does not repeatedly refresh more often than the background interval', () => {
+    expect(shouldAutoRefresh({ ...idleState, lastRefreshAt: idleState.now - AUTO_REFRESH_REPEAT_MS + 1 })).toBe(false);
+  });
+
+  it.each([
+    ['disconnected', { connected: false }],
+    ['busy', { busy: true }],
+    ['editing', { editing: true }],
+    ['dragging', { dragging: true }],
+    ['hidden', { visible: false }]
+  ])('pauses while %s', (_name, change) => {
+    expect(shouldAutoRefresh({ ...idleState, ...change })).toBe(false);
+  });
+});

app/src/lib/auto-refresh.ts

@@ -0,0 +1,23 @@
+export const AUTO_REFRESH_IDLE_MS = 10_000;
+export const AUTO_REFRESH_REPEAT_MS = 30_000;
+
+export interface AutoRefreshState {
+  now: number;
+  lastInteractionAt: number;
+  lastRefreshAt: number;
+  connected: boolean;
+  busy: boolean;
+  editing: boolean;
+  dragging: boolean;
+  visible: boolean;
+}
+
+export function shouldAutoRefresh(state: AutoRefreshState): boolean {
+  return state.connected
+    && state.visible
+    && !state.busy
+    && !state.editing
+    && !state.dragging
+    && state.now - state.lastInteractionAt >= AUTO_REFRESH_IDLE_MS
+    && state.now - state.lastRefreshAt >= AUTO_REFRESH_REPEAT_MS;
+}