From 3b7f4f723876473af74aa3bb9ba58db0f4bf3c37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Rebelo?= <joserebelo@outlook.com>
Date: Mon, 24 Jul 2023 18:16:23 +0100
Subject: [PATCH] Allow for gatt write request responses

Allow for support classes to send a write request response to the
device, fi requested. The standard actually expects this to happen, but
Gadgetbridge did not originally support it, so there are concerns that
enabling this globally will cause issues for devices that do not expect
the response.

See also: https://codeberg.org/Freeyourgadget/Gadgetbridge/pulls/2831#issuecomment-941568
---
 .../btle/AbstractBTLEDeviceSupport.java        | 14 ++++++++++++++
 .../gadgetbridge/service/btle/BtLEQueue.java   | 18 +++++++++++++++---
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java
index 79566f3bf..0ef82d27e 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java
@@ -79,6 +79,7 @@ public abstract class AbstractBTLEDeviceSupport extends AbstractDeviceSupport im
             mQueue = new BtLEQueue(getBluetoothAdapter(), getDevice(), this, this, getContext(), mSupportedServerServices);
             mQueue.setAutoReconnect(getAutoReconnect());
             mQueue.setImplicitGattCallbackModify(getImplicitCallbackModify());
+            mQueue.setSendWriteRequestResponse(getSendWriteRequestResponse());
         }
         return mQueue.connect();
     }
@@ -89,6 +90,19 @@ public abstract class AbstractBTLEDeviceSupport extends AbstractDeviceSupport im
         }
     }
 
+    /**
+     * Whether to send a write request response to the device, if requested. The standard actually
+     * expects this to happen, but Gadgetbridge did not originally support it. This is set to false
+     * to prevent breaking devices that are somehow not expecting the response.
+     * <p>
+     * See also: https://codeberg.org/Freeyourgadget/Gadgetbridge/pulls/2831#issuecomment-941568
+     *
+     * @return whether to send write request responses, if a response is requested
+     */
+    public boolean getSendWriteRequestResponse() {
+        return false;
+    }
+
     @Override
     public void setAutoReconnect(boolean enable) {
         super.setAutoReconnect(enable);
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/BtLEQueue.java b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/BtLEQueue.java
index 81c19ab46..78d64ee29 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/BtLEQueue.java
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/BtLEQueue.java
@@ -82,6 +82,7 @@ public final class BtLEQueue {
     private final InternalGattServerCallback internalGattServerCallback;
     private boolean mAutoReconnect;
     private boolean mImplicitGattCallbackModify = true;
+    private boolean mSendWriteRequestResponse = false;
 
     private Thread dispatchThread = new Thread("Gadgetbridge GATT Dispatcher") {
 
@@ -221,6 +222,10 @@ public final class BtLEQueue {
         mImplicitGattCallbackModify = enable;
     }
 
+    public void setSendWriteRequestResponse(final boolean enable) {
+        mSendWriteRequestResponse = enable;
+    }
+
     protected boolean isConnected() {
         return mGbDevice.isConnected();
     }
@@ -756,8 +761,12 @@ public final class BtLEQueue {
                 return;
             }
             LOG.debug("characteristic write request: " + device.getAddress() + " characteristic: " + characteristic.getUuid());
+            boolean success = false;
             if (getCallbackToUse() != null) {
-                getCallbackToUse().onCharacteristicWriteRequest(device, requestId, characteristic, preparedWrite, responseNeeded, offset, value);
+                success = getCallbackToUse().onCharacteristicWriteRequest(device, requestId, characteristic, preparedWrite, responseNeeded, offset, value);
+            }
+            if (responseNeeded && mSendWriteRequestResponse) {
+                mBluetoothGattServer.sendResponse(device, requestId, success ? BluetoothGatt.GATT_SUCCESS : BluetoothGatt.GATT_FAILURE, 0, new byte[0]);
             }
         }
 
@@ -778,10 +787,13 @@ public final class BtLEQueue {
                 return;
             }
             LOG.debug("onDescriptorWriteRequest: " + device.getAddress());
+            boolean success = false;
             if(getCallbackToUse() != null) {
-                getCallbackToUse().onDescriptorWriteRequest(device, requestId, descriptor, preparedWrite, responseNeeded, offset, value);
+                success = getCallbackToUse().onDescriptorWriteRequest(device, requestId, descriptor, preparedWrite, responseNeeded, offset, value);
+            }
+            if (responseNeeded && mSendWriteRequestResponse) {
+                mBluetoothGattServer.sendResponse(device, requestId, success ? BluetoothGatt.GATT_SUCCESS : BluetoothGatt.GATT_FAILURE, 0, new byte[0]);
             }
         }
     }
-
 }