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Waking the server' + 'This can take a few seconds on first open.' + '

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'; (document.body || document.documentElement).appendChild(el); } // Surface the "Waking up" message and start an animated dots ticker so the // visitor sees that the app is actively working, not frozen. function showWaking(){ if (wokenShown) return; var el = document.getElementById('sb-boot-cover'); if (!el) return; wokenShown = true; el.className = (el.className ? el.className + ' ' : '') + 'sbc-woken'; try { var dots = el.querySelector('.sbc-dots'); if (dots) { var n = 0; var iv = setInterval(function(){ if (removed) { clearInterval(iv); return; } n = (n + 1) % 4; dots.textContent = new Array(n + 1).join('.'); }, 450); } } catch (e) {} } function hideCover(){ if (removed) return; removed = true; try { sessionStorage.setItem('sb_splash_shown', '1'); } catch (e) {} var el = document.getElementById('sb-boot-cover'); if (!el) return; el.style.opacity = '0'; setTimeout(function(){ if (el && el.parentNode) el.parentNode.removeChild(el); }, 450); } // Has the real server HTML painted behind the cover?

and the // scroll sentinel are server-rendered on every page, so their presence // means the app document has arrived and it is safe to reveal it. function contentReady(){ try { return !!(document.getElementById('scroll-sentinel') || document.querySelector('header')); } catch (e) { return false; } } // The single decision point. Returns true once the cover is (being) removed. // // Removal rules, in priority order: // 1. HARD_MS reached -> remove unconditionally (never trap the user). // 2. Content present + past MIN_MS + document parsed -> reveal the app. // 3. Otherwise, if past WAKE_MS, show the "Waking up" message and KEEP // the cover (so we never fade to a blank white page while the cold // server is still starting). We only ever reveal real content or the // hard-cap fallback -- never emptiness. function maybeHide(){ if (removed) return true; var e = now() - START; if (e >= HARD_MS) { hideCover(); return true; } // absolute ceiling if (e >= MIN_MS && contentReady()) { // app is visible if (document.readyState === 'interactive' || document.readyState === 'complete') { hideCover(); return true; } } if (e >= WAKE_MS && !contentReady()) { showWaking(); } // cold server: reassure return false; } // Last-resort auto-reload: if the real content genuinely never arrives // (dropped request, cold server that timed out), reload the page ONCE so // the visitor is not forced to close and reopen the browser by hand. // Guarded by sessionStorage so we never loop-reload. function maybeAutoReload(){ if (reloadDone) return; if (contentReady()) return; // content did arrive -> nothing to do reloadDone = true; var already = false; try { already = !!sessionStorage.getItem('sb_boot_reloaded'); } catch (e) {} if (already) { hideCover(); return; } // already retried once -> give up gracefully try { sessionStorage.setItem('sb_boot_reloaded', '1'); } catch (e) {} try { location.reload(); } catch (e) { hideCover(); } } // rAF watchdog: unlike setTimeout, rAF pauses while the PWA is backgrounded // and RESUMES on return to the foreground -- so when the user reopens the // app the very next frame re-evaluates elapsed time and clears an overdue // cover immediately (this is what used to trap the atom on resume). function tick(){ if (maybeHide()) return; try { requestAnimationFrame(tick); } catch (e) { setTimeout(tick, 60); } // engines without rAF } // If already shown this session, skip the animation entirely. var already = false; try { already = !!sessionStorage.getItem('sb_splash_shown'); } catch (e) {} if (already) return; // If a successful boot happened earlier, clear the one-shot reload guard so // future genuine cold starts can still auto-retry once. try { if (sessionStorage.getItem('sb_splash_shown')) sessionStorage.removeItem('sb_boot_reloaded'); } catch (e) {} // Build as soon as exists. if (document.body) buildCover(); else document.addEventListener('DOMContentLoaded', buildCover); // MutationObserver: fires the instant the server HTML (header / sentinel) // is inserted, independent of any clock. This is the fastest, most reliable // "content arrived" signal and does not depend on throttled timers. try { if (window.MutationObserver) { var mo = new MutationObserver(function(){ if (contentReady()) { maybeHide(); if (removed) { try { mo.disconnect(); } catch (e) {} } } }); var startObserve = function(){ try { mo.observe(document.body || document.documentElement, { childList: true, subtree: true }); } catch (e) {} }; if (document.body) startObserve(); else document.addEventListener('DOMContentLoaded', startObserve); } } catch (e) {} // Start the watchdog and wire the belt-and-braces triggers. try { requestAnimationFrame(tick); } catch (e) { setTimeout(tick, 60); } document.addEventListener('DOMContentLoaded', maybeHide); window.addEventListener('load', maybeHide); document.addEventListener('visibilitychange', function(){ if (document.visibilityState === 'visible') maybeHide(); }); // pageshow fires on back/forward-cache restores -- exactly the "go back and // reopen" case -- so re-evaluate removal there too. window.addEventListener('pageshow', maybeHide); // Timer safety net (works even if rAF is starved): reassure at WAKE_MS, // guarantee removal at HARD_MS, and auto-reload once at RELOAD_MS. setTimeout(function(){ if (!removed && !contentReady()) showWaking(); }, WAKE_MS + 50); setTimeout(hideCover, HARD_MS + 400); setTimeout(maybeAutoReload, RELOAD_MS); } catch (e) { try { var el = document.getElementById('sb-boot-cover'); if (el && el.parentNode) el.parentNode.removeChild(el); } catch (e2) {} } })();

Dr. Vibhu T S

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