From b5eb54fc442e926fc2743e9df873d811c0d1fab0 Mon Sep 17 00:00:00 2001
From: Evelyn Eastmond <evhan55@gmail.com>
Date: Thu, 7 Feb 2019 16:18:56 -0500
Subject: [PATCH] Resolves 1975: Vernier gdxfor extension should disconnect on
 sensor timeout.

---
 src/extensions/scratch3_gdx_for/index.js | 32 +++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/src/extensions/scratch3_gdx_for/index.js b/src/extensions/scratch3_gdx_for/index.js
index 910347e14..f0a1b5882 100644
--- a/src/extensions/scratch3_gdx_for/index.js
+++ b/src/extensions/scratch3_gdx_for/index.js
@@ -25,6 +25,18 @@ const BLEUUID = {
     responseChar: 'b41e6675-a329-40e0-aa01-44d2f444babe'
 };
 
+/**
+ * A time interval to wait (in milliseconds) before reporting to the BLE socket
+ * that data has stopped coming from the peripheral.
+ */
+const BLETimeout = 4500;
+
+/**
+ * A string to report to the BLE socket when the GdxFor has stopped receiving data.
+ * @type {string}
+ */
+const BLEDataStoppedError = 'Force and Acceleration extension stopped receiving data';
+
 /**
  * Sensor ID numbers for the GDX-FOR.
  */
@@ -140,6 +152,13 @@ class GdxFor {
             spinSpeedZ: 0
         };
 
+        /**
+         * Interval ID for data reading timeout.
+         * @type {number}
+         * @private
+         */
+        this._timeoutID = null;
+
         this.disconnect = this.disconnect.bind(this);
         this._onConnect = this._onConnect.bind(this);
     }
@@ -160,7 +179,7 @@ class GdxFor {
             optionalServices: [
                 BLEUUID.service
             ]
-        }, this._onConnect);
+        }, this._onConnect, this.disconnect);
     }
 
     /**
@@ -178,6 +197,7 @@ class GdxFor {
      * Disconnect from the GDX FOR.
      */
     disconnect () {
+        window.clearInterval(this._timeoutID);
         this._sensors = {
             force: 0,
             accelerationX: 0,
@@ -228,6 +248,10 @@ class GdxFor {
                         this._onSensorValueChanged(s);
                     });
                 });
+                this._timeoutID = window.setInterval(
+                    () => this._scratchLinkSocket.handleDisconnectError(BLEDataStoppedError),
+                    BLETimeout
+                );
             });
 
             // Start device
@@ -266,6 +290,12 @@ class GdxFor {
             this._sensors.spinSpeedZ = this._spinSpeedFromGyro(sensor.value);
             break;
         }
+        // cancel disconnect timeout and start a new one
+        window.clearInterval(this._timeoutID);
+        this._timeoutID = window.setInterval(
+            () => this._scratchLinkSocket.handleDisconnectError(BLEDataStoppedError),
+            BLETimeout
+        );
     }
 
     _spinSpeedFromGyro (val) {