fix: simplify waitForActivation with settled flag pattern

refactor to use idempotent succeed/fail helpers that prevent double
resolution. check worker state after adding listener to close race
condition window where worker could activate before listener attached.

Author: lidel

src/lib/register-service-worker.ts

@@ -15,26 +15,39 @@ export async function registerServiceWorker (): Promise<ServiceWorkerRegistratio
 
 async function waitForActivation (swRegistration: ServiceWorkerRegistration): Promise<ServiceWorkerRegistration> {
   return new Promise((resolve, reject) => {
+    let settled = false
+
+    const succeed = (): void => {
+      if (settled) { return }
+      settled = true
+      clearTimeout(timeoutId)
+      resolve(swRegistration)
+    }
+
+    const fail = (msg: string): void => {
+      if (settled) { return }
+      settled = true
+      clearTimeout(timeoutId)
+      reject(new Error(msg))
+    }
+
     const timeoutId = setTimeout(() => {
-      reject(new Error('Service worker failed to activate within 30 seconds. Refresh the page to retry.'))
+      fail('Service worker failed to activate within 30 seconds. Refresh the page to retry.')
     }, 30_000)
 
-    const onStateChange = (e: Event): void => {
-      const sw = e.target as ServiceWorker
-      if (sw.state === 'activated') {
-        clearTimeout(timeoutId)
-        resolve(swRegistration)
-      } else if (sw.state === 'redundant') {
-        clearTimeout(timeoutId)
-        reject(new Error('Service worker became redundant. Refresh the page to retry.'))
-      }
+    const trackWorker = (sw: ServiceWorker | null): void => {
+      if (sw == null) { return }
+      sw.addEventListener('statechange', () => {
+        if (sw.state === 'activated') { succeed() } else if (sw.state === 'redundant') { fail('Service worker became redundant. Refresh the page to retry.') }
+      })
+      if (sw.state === 'activated') { succeed() }
     }
 
-    // track workers that may already be installing or waiting
-    swRegistration.installing?.addEventListener('statechange', onStateChange)
-    swRegistration.waiting?.addEventListener('statechange', onStateChange)
+    trackWorker(swRegistration.installing)
+    trackWorker(swRegistration.waiting)
+    trackWorker(swRegistration.active)
     swRegistration.addEventListener('updatefound', () => {
-      swRegistration.installing?.addEventListener('statechange', onStateChange)
+      trackWorker(swRegistration.installing)
     })
   })
 }