EV3/Microbit critical fixes for code freeze (#1354)

* Resolves - BLESession and BTSession should emit PERIPHERAL_SCAN_TIMEOUT #1348.

* Resolves - BLESession should handle 'could not find service' error #1350.

* Resolves - BTSession should handle 'no peripheral connected' error #1351.

* Fixing a typo that caused device scan timeout bugs.

* Resolves - Add casting and clamping throughout the EV3 extension #1352.

* Fixing a linting error.

* Further fixes for issue #1351.

src/io/bleSession.js

@@ -22,11 +22,11 @@ class BLESession extends JSONRPCWebSocket {
 
         this._availablePeripherals = {};
         this._connectCallback = connectCallback;
+        this._connected = false;
         this._characteristicDidChangeCallback = null;
         this._deviceOptions = deviceOptions;
+        this._discoverTimeoutID = null;
         this._runtime = runtime;
-
-        this._connected = false;
     }
 
     /**
@@ -35,7 +35,8 @@ class BLESession extends JSONRPCWebSocket {
      */
     requestDevice () {
         if (this._ws.readyState === 1) { // is this needed since it's only called on ws.onopen?
-            // TODO: start a 'discover' timeout
+            this._availablePeripherals = {};
+            this._discoverTimeoutID = window.setTimeout(this._sendDiscoverTimeout.bind(this), 15000);
             this.sendRemoteRequest('discover', this._deviceOptions)
                 .catch(e => this._sendError(e)); // never reached?
         }
@@ -88,7 +89,10 @@ class BLESession extends JSONRPCWebSocket {
                 this._runtime.constructor.PERIPHERAL_LIST_UPDATE,
                 this._availablePeripherals
             );
-            // TODO: cancel a discover timeout if one is active
+            if (this._discoverTimeoutID) {
+                // TODO: window?
+                window.clearTimeout(this._discoverTimeoutID);
+            }
             break;
         case 'characteristicDidChange':
             this._characteristicDidChangeCallback(params.message);
@@ -115,8 +119,10 @@ class BLESession extends JSONRPCWebSocket {
             params.startNotifications = true;
         }
         this._characteristicDidChangeCallback = onCharacteristicChanged;
-        return this.sendRemoteRequest('read', params);
-        // TODO: handle error here
+        return this.sendRemoteRequest('read', params)
+            .catch(e => {
+                this._sendError(e);
+            });
     }
 
     /**
@@ -132,7 +138,10 @@ class BLESession extends JSONRPCWebSocket {
         if (encoding) {
             params.encoding = encoding;
         }
-        return this.sendRemoteRequest('write', params);
+        return this.sendRemoteRequest('write', params)
+            .catch(e => {
+                this._sendError(e);
+            });
     }
 
     _sendError (e) {
@@ -140,6 +149,10 @@ class BLESession extends JSONRPCWebSocket {
         log.error(`BLESession error: ${JSON.stringify(e)}`);
         this._runtime.emit(this._runtime.constructor.PERIPHERAL_ERROR);
     }
+
+    _sendDiscoverTimeout () {
+        this._runtime.emit(this._runtime.constructor.PERIPHERAL_SCAN_TIMEOUT);
+    }
 }
 
 module.exports = BLESession;