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import { invalidateAll } from '$app/navigation';
import { navigating, page } from '$app/stores';
import { get } from 'svelte/store';
import { shouldAutoRefresh } from '$lib/shared/refresh-policy';
/** Away for at least this long before refocus re-runs the page load. */
const MIN_AWAY_MS = 10_000;
/** Poll cadence: near-live for a shared list, cheap for one open tab. */
const POLL_INTERVAL_MS = 15_000;
/**
* Keeps the current page near-live: polls the server while the tab is visible,
* and refetches on refocus after an absence. Call from `onMount`; the returned
* function tears the listeners and timer down.
*/
export function startAutoRefresh(): () => void {
// When the tab stopped being the active one; null while it is active.
let deactivatedAt: number | null = null;
const conditions = () => ({
routeId: get(page).route.id,
visible: document.visibilityState === 'visible',
online: navigator.onLine,
navigating: get(navigating) !== null,
});
const deactivate = () => {
deactivatedAt ??= Date.now();
};
const activate = () => {
if (deactivatedAt === null) return;
const awayMs = Date.now() - deactivatedAt;
deactivatedAt = null;
if (awayMs >= MIN_AWAY_MS && shouldAutoRefresh(conditions()))
void invalidateAll();
};
const onVisibilityChange = () => {
if (document.visibilityState === 'hidden') deactivate();
else activate();
};
const timer = setInterval(() => {
if (shouldAutoRefresh(conditions())) void invalidateAll();
}, POLL_INTERVAL_MS);
document.addEventListener('visibilitychange', onVisibilityChange);
window.addEventListener('blur', deactivate);
window.addEventListener('focus', activate);
return () => {
clearInterval(timer);
document.removeEventListener('visibilitychange', onVisibilityChange);
window.removeEventListener('blur', deactivate);
window.removeEventListener('focus', activate);
};
}
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