Pebble 2: fixes for experimental client only gatt code

This basically makes sure that
- only one gatt write operation is in progress
- data is not sent from within callbacks to prevent a deadlock when waiting for a nre callback that cant happen yet beause the current has not been retuned

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/pebble/ble/PebbleGATTClient.java

@@ -28,6 +28,7 @@ import org.slf4j.LoggerFactory;
 
 import java.lang.reflect.Method;
 import java.util.UUID;
+import java.util.concurrent.CountDownLatch;
 
 import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.util.GB;
@@ -62,6 +63,8 @@ class PebbleGATTClient extends BluetoothGattCallback {
     private boolean removeBond = false;
     private BluetoothGatt mBluetoothGatt;
 
+    private CountDownLatch mWaitWriteCompleteLatch;
+
     PebbleGATTClient(PebbleLESupport pebbleLESupport, Context context, BluetoothDevice btDevice) {
         mContext = context;
         mPebbleLESupport = pebbleLESupport;
@@ -119,9 +122,16 @@ class PebbleGATTClient extends BluetoothGattCallback {
         if (!mPebbleLESupport.isExpectedDevice(gatt.getDevice())) {
             return;
         }
-
-        LOG.info("onCharacteristicWrite() " + characteristic.getUuid());
-        if (characteristic.getUuid().equals(PAIRING_TRIGGER_CHARACTERISTIC) || characteristic.getUuid().equals(CONNECTIVITY_CHARACTERISTIC)) {
+        if (characteristic.getUuid().equals(PPOGATT_CHARACTERISTIC_WRITE)) {
+            if (status != BluetoothGatt.GATT_SUCCESS) {
+                LOG.error("something went wrong when writing to PPoGATT characteristics");
+            }
+            if (mWaitWriteCompleteLatch != null) {
+                mWaitWriteCompleteLatch.countDown();
+            } else {
+                LOG.warn("mWaitWriteCompleteLatch is null!");
+            }
+        } else if (characteristic.getUuid().equals(PAIRING_TRIGGER_CHARACTERISTIC) || characteristic.getUuid().equals(CONNECTIVITY_CHARACTERISTIC)) {
             //mBtDevice.createBond(); // did not work when last tried
 
             if (oldPebble) {
@@ -266,13 +276,20 @@ class PebbleGATTClient extends BluetoothGattCallback {
     }
 
     synchronized void sendDataToPebble(byte[] data) {
+        mWaitWriteCompleteLatch = new CountDownLatch(1);
         writeCharacteristics.setValue(data.clone());
-        mBluetoothGatt.writeCharacteristic(writeCharacteristics);
-    }
 
-    synchronized void sendAckToPebble(int serial) {
-        writeCharacteristics.setValue(new byte[]{(byte) (((serial << 3) | 1) & 0xff)});
-        mBluetoothGatt.writeCharacteristic(writeCharacteristics);
+        boolean success = mBluetoothGatt.writeCharacteristic(writeCharacteristics);
+        if (!success) {
+            LOG.error("could not send data to pebble (error writing characteristic)");
+        } else {
+            try {
+                mWaitWriteCompleteLatch.await();
+            } catch (InterruptedException e) {
+                LOG.warn("interrupted while waiting for write complete latch");
+            }
+        }
+        mWaitWriteCompleteLatch = null;
     }
 
     public void close() {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/pebble/ble/PebbleGATTServer.java

@@ -52,7 +52,9 @@ class PebbleGATTServer extends BluetoothGattServerCallback {
 
     boolean initialize() {
         BluetoothManager bluetoothManager = (BluetoothManager) mContext.getSystemService(Context.BLUETOOTH_SERVICE);
-
+        if (bluetoothManager == null) {
+            return false;
+        }
         mBluetoothGattServer = bluetoothManager.openGattServer(mContext, this);
         if (mBluetoothGattServer == null) {
             return false;
@@ -76,12 +78,6 @@ class PebbleGATTServer extends BluetoothGattServerCallback {
         mBluetoothGattServer.notifyCharacteristicChanged(mBtDevice, writeCharacteristics, false);
     }
 
-    synchronized void sendAckToPebble(int serial) {
-        writeCharacteristics.setValue(new byte[]{(byte) (((serial << 3) | 1) & 0xff)});
-
-        mBluetoothGattServer.notifyCharacteristicChanged(mBtDevice, writeCharacteristics, false);
-    }
-
     public void onCharacteristicReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattCharacteristic characteristic) {
         if (!mPebbleLESupport.isExpectedDevice(device)) {
             return;

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/pebble/ble/PebbleLESupport.java

@@ -18,6 +18,8 @@ package nodomain.freeyourgadget.gadgetbridge.service.devices.pebble.ble;
 
 import android.bluetooth.BluetoothDevice;
 import android.content.Context;
+import android.os.Handler;
+import android.os.HandlerThread;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -39,9 +41,11 @@ public class PebbleLESupport {
     private PipedOutputStream mPipedOutputStream;
     private int mMTU = 20;
     private int mMTULimit = Integer.MAX_VALUE;
-    public boolean clientOnly = false; // currently broken, and only possible for Pebble 2
+    public boolean clientOnly = false; // currently experimental, and only possible for Pebble 2
     private boolean mIsConnected = false;
     private CountDownLatch mPPAck;
+    private HandlerThread mWriteHandlerThread;
+    private Handler mWriteHandler;
 
     public PebbleLESupport(Context context, final BluetoothDevice btDevice, PipedInputStream pipedInputStream, PipedOutputStream pipedOutputStream) throws IOException {
         mBtDevice = btDevice;
@@ -53,6 +57,11 @@ public class PebbleLESupport {
         } catch (IOException e) {
             LOG.warn("could not connect input stream");
         }
+
+        mWriteHandlerThread = new HandlerThread("write handler thread");
+        mWriteHandlerThread.start();
+        mWriteHandler = new Handler(mWriteHandlerThread.getLooper());
+
         mMTULimit = GBApplication.getPrefs().getInt("pebble_mtu_limit", 512);
         mMTULimit = Math.max(mMTULimit, 20);
         mMTULimit = Math.min(mMTULimit, 512);
@@ -102,6 +111,9 @@ public class PebbleLESupport {
             mPipedOutputStream.close();
         } catch (IOException ignore) {
         }
+        if (mWriteHandlerThread != null) {
+            mWriteHandlerThread.quit();
+        }
     }
 
     private synchronized void createPipedInputReader() {
@@ -166,19 +178,21 @@ public class PebbleLESupport {
     }
 
     private void sendAckToPebble(int serial) {
-        if (mPebbleGATTServer != null) {
-            mPebbleGATTServer.sendAckToPebble(serial);
-        } else {
-            mPebbleGATTClient.sendAckToPebble(serial);
-        }
+        sendDataToPebble(new byte[]{(byte) (((serial << 3) | 1) & 0xff)});
     }
 
-    private void sendDataToPebble(byte[] bytes) {
+    private synchronized void sendDataToPebble(final byte[] bytes) {
         if (mPebbleGATTServer != null) {
             mPebbleGATTServer.sendDataToPebble(bytes);
         } else {
+            // For now only in experimental client only code
+            mWriteHandler.post(new Runnable() {
+                @Override
+                public void run() {
                     mPebbleGATTClient.sendDataToPebble(bytes);
                 }
+            });
+        }
     }
 
     private class PipeReader extends Thread {