retry establishing connection when the background service worker restarts

retry-able-connection.ts

// Background service worker

function backgroundServiceHandshake() {
  chrome.runtime.onMessage.addListener((message: any, _: any, sendResponse: (response: 'ack') => void) => {
    if (message === 'syn') {
      if (!isInitialized) {
        initializeService();
        isInitialized = true;
      }
      sendResponse('ack');
    }
    // Otherwise, the message is irrelevant and ignored
  });
}

// Other service -- either Popup or DApp

let otherServicePort = chrome.runtime.connect({ name }) as RuntimePort;
const messageQueue: any[] = [];

// Reconnect on disconnecting from background
port.onDisconnect.addListener(() => {
  port = chrome.runtime.connect({ name: this.name }) as RuntimePort;
  isBackgroundServiceListening = false;
  
  // Retry handshake
  otherServiceHandshake();
});


function otherServiceSender(data: any) {
  if (isBackgroundServiceListening) {
    otherServicePort.postMessage(data);
  } else {
    // If background is down, queue messages
    messageQueue.push(data);
  }
}

function sendPendingMessages() {
  // Empty pending messages' queue
  if (messageQueue.length > 0) {
    const currMessageQueue = messageQueue.splice(0, messageQueue.length);
    for (const message of currMessageQueue) {
      otherServiceSender(message);
    }
  }
}

function otherServiceHandshake() {
  chrome.runtime.sendMessage('syn', (message: any) => {
    if (message === 'ack') {
      // Send queued messages
      sendPendingMessages();
      isBackgroundServiceListening = true;
    }
  });
}