Only poll USB devices list when a change is detected

packages/hw-transport-node-hid/package.json

@@ -26,7 +26,8 @@
   "license": "Apache-2.0",
   "dependencies": {
     "@ledgerhq/hw-transport": "^4.19.0",
-    "node-hid": "^0.7.2"
+    "node-hid": "^0.7.2",
+    "usb-detection": "^3.1.0"
   },
   "devDependencies": {
     "flow-bin": "^0.68.0",

packages/hw-transport-node-hid/src/TransportNodeHid.js

@@ -28,6 +28,7 @@ function defer<T>(): Defer<T> {
 
 let listenDevicesPollingInterval = 500;
 let listenDevicesPollingSkip = () => false;
+let listenDevicesDebugMode = false;
 
 /**
  * node-hid Transport implementation
@@ -68,6 +69,10 @@ export default class TransportNodeHid extends Transport<string> {
     listenDevicesPollingSkip = conditionToSkip;
   };
 
+  static setListenDevicesDebugMode = (bool: boolean) => {
+    listenDevicesDebugMode = bool;
+  };
+
   /**
    */
   static listen = (
@@ -85,7 +90,8 @@ export default class TransportNodeHid extends Transport<string> {
     });
     const { events, stop } = listenDevices(
       listenDevicesPollingInterval,
-      listenDevicesPollingSkip
+      listenDevicesPollingSkip,
+      listenDevicesDebugMode
     );
 
     const onAdd = device => {

packages/hw-transport-node-hid/src/listenDevices.js

@@ -1,21 +1,31 @@
 // @flow
 
 import EventEmitter from "events";
+import usbDetect from "usb-detection";
 import getDevices from "./getDevices";
 
+const VENDOR_ID = 11415; // Ledger's Vendor ID for filtering
+const MAX_ATTEMPTS = 10;
+
 export default (
   delay: number,
-  listenDevicesPollingSkip: () => boolean
+  listenDevicesPollingSkip: () => boolean,
+  debugMode: boolean
 ): {
   events: EventEmitter,
   stop: () => void
 } => {
   const events = new EventEmitter();
   events.setMaxListeners(0);
 
-  let timeoutDetection;
   let listDevices = getDevices();
 
+  const debug = (...args) => {
+    if (debugMode && args[0]) {
+      console.log("[listenDevices]", ...args);
+    }
+  };
+
   const flatDevice = d => d.path;
 
   const getFlatDevices = () => [
@@ -27,37 +37,93 @@ export default (
 
   let lastDevices = getFlatDevices();
 
-  const checkDevices = () => {
+  const poll = (type, attempt = 1) => {
+    let changeFound = false;
+
     if (!listenDevicesPollingSkip()) {
+      debug(`Polling for ${type} [attempt ${attempt}/${MAX_ATTEMPTS}]`);
+
       const currentDevices = getFlatDevices();
 
-      const newDevices = currentDevices.filter(d => !lastDevices.includes(d));
-      const removeDevices = lastDevices.filter(
-        d => !currentDevices.includes(d)
-      );
+      if (type === "add") {
+        const newDevices = currentDevices.filter(d => !lastDevices.includes(d));
+
+        if (newDevices.length > 0) {
+          debug("New device found:", newDevices);
+
+          listDevices = getDevices();
+          events.emit("add", getDeviceByPaths(newDevices));
 
-      if (newDevices.length > 0) {
-        listDevices = getDevices();
-        events.emit("add", getDeviceByPaths(newDevices));
+          changeFound = true;
+        } else {
+          debug("No new device found");
+        }
       }
 
-      if (removeDevices.length > 0) {
-        events.emit("remove", getDeviceByPaths(removeDevices));
-        listDevices = listDevices.filter(
-          d => !removeDevices.includes(flatDevice(d))
+      if (type === "remove") {
+        const removeDevices = lastDevices.filter(
+          d => !currentDevices.includes(d)
         );
+
+        if (removeDevices.length > 0) {
+          debug("Removed device found:", removeDevices);
+
+          events.emit("remove", getDeviceByPaths(removeDevices));
+          listDevices = listDevices.filter(
+            d => !removeDevices.includes(flatDevice(d))
+          );
+
+          changeFound = true;
+        } else {
+          debug("No removed device found");
+        }
+      }
+
+      if (changeFound) {
+        lastDevices = currentDevices;
+      } else {
+        if (attempt < MAX_ATTEMPTS) {
+          const newDelay = delay * attempt;
+
+          debug(`Repolling ${type} in ${newDelay}ms`);
+
+          setTimeout(() => {
+            poll(type, attempt + 1);
+          }, newDelay);
+        } else {
+          debug(`Giving up after ${attempt} attempts`);
+        }
       }
+    } else {
+      debug(`Polling skipped, retrying in ${delay}ms`);
 
-      lastDevices = currentDevices;
+      setTimeout(() => {
+        poll(type);
+      }, delay);
     }
-    setTimeout(checkDevices, delay);
   };
 
-  timeoutDetection = setTimeout(checkDevices, delay);
+  debug("Starting to monitor USB for ledger devices");
+  usbDetect.startMonitoring();
+
+  // Detect add
+  usbDetect.on(`add:${VENDOR_ID}`, device => {
+    debug("Device add detected:", device.deviceName);
+
+    poll("add");
+  });
+
+  // Detect remove
+  usbDetect.on(`remove:${VENDOR_ID}`, device => {
+    debug("Device removal detected:", device.deviceName);
+
+    poll("remove");
+  });
 
   return {
     stop: () => {
-      clearTimeout(timeoutDetection);
+      debug("Stopping USB monitoring");
+      usbDetect.stopMonitoring();
     },
     events
   };