Workaround for a disconnected worker on iOS

src/api/gramjs/worker/provider.ts

@@ -4,6 +4,7 @@ import { WorkerMessageEvent, ThenArg, OriginRequest } from './types';
 
 import { DEBUG } from '../../../config';
 import generateIdFor from '../../../util/generateIdFor';
+import { pause } from '../../../util/schedulers';
 
 type RequestStates = {
   messageId: string;
@@ -12,6 +13,9 @@ type RequestStates = {
   callback?: AnyToVoidFunction;
 };
 
+const HEALTH_CHECK_TIMEOUT = 1000; // 1 sec
+const HEALTH_CHECK_MIN_DELAY = 5 * 1000; // 5 sec
+
 let worker: Worker;
 const requestStates = new Map<string, RequestStates>();
 const requestStatesByCallback = new Map<AnyToVoidFunction, RequestStates>();
@@ -27,6 +31,10 @@ export function initApi(onUpdate: OnApiUpdate, initialArgs: ApiInitialArgs) {
 
     worker = new Worker(new URL('./worker.ts', import.meta.url));
     subscribeToWorker(onUpdate);
+
+    if (initialArgs.platform === 'iOS') {
+      setupIosHealthCheck();
+    }
   }
 
   return makeRequest({
@@ -104,7 +112,7 @@ function makeRequest(message: OriginRequest) {
     Object.assign(requestState, { resolve, reject });
   });
 
-  if (typeof payload.args[1] === 'function') {
+  if (('args' in payload) && typeof payload.args[1] === 'function') {
     const callback = payload.args.pop() as AnyToVoidFunction;
     requestState.callback = callback;
     requestStatesByCallback.set(callback, requestState);
@@ -125,3 +133,24 @@ function makeRequest(message: OriginRequest) {
 
   return promise;
 }
+
+const startedAt = Date.now();
+
+// Workaround for iOS sometimes stops interacting with worker
+function setupIosHealthCheck() {
+  window.addEventListener('focus', async () => {
+    try {
+      await Promise.race([
+        makeRequest({ type: 'ping' }),
+        pause(HEALTH_CHECK_TIMEOUT).then(() => Promise.reject(new Error('HEALTH_CHECK_TIMEOUT'))),
+      ]);
+    } catch (err) {
+      // eslint-disable-next-line no-console
+      console.error(err);
+
+      if (Date.now() - startedAt >= HEALTH_CHECK_MIN_DELAY) {
+        window.location.reload();
+      }
+    }
+  });
+}

src/api/gramjs/worker/types.ts

@@ -33,6 +33,9 @@ export type OriginRequest = {
   messageId?: string;
   name: keyof Methods;
   args: MethodArgs<keyof Methods>;
+} | {
+  type: 'ping';
+  messageId?: string;
 };
 
 export type OriginMessageData = OriginRequest | {

src/api/gramjs/worker/worker.ts

@@ -81,6 +81,14 @@ onmessage = async (message: OriginMessageEvent) => {
         cancelApiProgress(callback);
       }
 
+      break;
+    }
+    case 'ping': {
+      sendToOrigin({
+        type: 'methodResponse',
+        messageId: data.messageId!,
+      });
+
       break;
     }
   }