Implementing a BLE connection finder.

components/proximity_auth/ble/bluetooth_low_energy_connection_finder.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_LOW_ENERGY_CONNECTION_FINDER_H
+#define COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_LOW_ENERGY_CONNECTION_FINDER_H
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "components/proximity_auth/connection_finder.h"
+#include "device/bluetooth/bluetooth_adapter.h"
+#include "device/bluetooth/bluetooth_device.h"
+#include "device/bluetooth/bluetooth_discovery_session.h"
+#include "device/bluetooth/bluetooth_gatt_connection.h"
+
+namespace proximity_auth {
+
+// This ConnectionFinder implementation tries to find a Bluetooth connection to

[msarda, 2015/04/22 15:58:13]

This comment must be explicit about the fact that this class uses a Bluetooth
Low Energy connection. How about:
A connection finder that is specialized in finding a Bluetooth Low Energy remote
device. 

[sacomoto, 2015/04/24 14:04:56]

Done.

+// a remote device.
+class BluetoothLowEnergyConnectionFinder
+    : public ConnectionFinder,
+      public device::BluetoothAdapter::Observer {
+ public:
+  BluetoothLowEnergyConnectionFinder(const std::string& remote_service_uuid);
+  ~BluetoothLowEnergyConnectionFinder() override;
+
+  // Finds a connection the remote device, only the first one is functional.
+  void Find(const device::BluetoothDevice::GattConnectionCallback&

[msarda, 2015/04/22 15:58:13]

Please add a comment explaining that this method can be called only once. BTW,
is that the contract for proximity_auth::ConnectionFinder?

[msarda, 2015/04/22 15:58:13]

I somehow feel we need to add an empty implementation of
proximity_auth::Connection and use the Find method. I think that would avoid
unnecessary changes in ProximityAuthBleSystem.

[sacomoto, 2015/04/24 14:04:56]

Yes. 

Actually, I think it would be better to have the Find method in the class
constructor, that way we guarantee that
"BluetoothLowEnergyConnectionFinder::StartDiscoverySession" is only called once.
But this doesn't match the ConnectionFinder interface. I think they will do it
at some point, there is a comment about it in ConnectionFinder, when they do it,
I'll reflect the changes here.

[sacomoto, 2015/04/24 14:04:57]

My next CL already implements proximity_auth::Connection and there we only need
a single Find method. Can we leave like this for the moment?

[msarda, 2015/04/24 14:12:16]

Ok.

+                connection_callback);
+  void Find(const ConnectionCallback& connection_callback) override;
+
+ protected:
+  // Observer for device::BluetoothAdapter::Observer
+  void DeviceAdded(device::BluetoothAdapter* adapter,
+                   device::BluetoothDevice* device) override;
+
+ private:
+  // Callback to be called when the Bluetooth adapter is initialized.
+  void OnAdapterInitialized(scoped_refptr<device::BluetoothAdapter> adapter);

[msarda, 2015/04/22 15:58:13]

Why is this private and DeviceAdded is protected?

[sacomoto, 2015/04/24 14:04:57]

DeviceAdded is part of the BluetoothAdapter::Observer interface. The current
object is added as an observer of |adapter_| to receive the notification when a
new device is added. So, DeviceAdded should be called from outside the
BluetoothLowEnergyConnectionFinder, whereas OnAdapterInitialized is only called
internally.

+
+  // Callback to be called when a new discovery session is started.
+  void OnDiscoverySessionStarted(
+      scoped_ptr<device::BluetoothDiscoverySession> discovery_session);
+
+  // Starts a discovery session for |adapter_|.
+  void StartDiscoverySession();
+
+  // Stops the discovery session given by |discovery_session_|.
+  void StopDiscoverySession();
+
+  // Checks if a service with |service_uuid| is offered by |remote_device|.
+  bool HasService(device::BluetoothDevice* remote_device);
+
+  // Creates a connection with |remote_device|, the |connection_callback_| will

[msarda, 2015/04/22 15:58:13]

s/a connection/a GATT connection
s/, the |coonnection_callback_|/. |connection_callback_|

[sacomoto, 2015/04/24 14:04:57]

Done.

+  // be called once the connection is established.
+  void CreateConnection(device::BluetoothDevice* remote_device);
+
+  // The uuid of the service it looks for to establish a GattConnection.
+  device::BluetoothUUID remote_service_uuid_;
+
+  // The Bluetooth adapter over which the Bluetooth connection will be made.
+  scoped_refptr<device::BluetoothAdapter> adapter_;
+
+  // The discovery session associated to this object.
+  scoped_ptr<device::BluetoothDiscoverySession> discovery_session_;
+
+  // Callback called when the connection is established.
+  device::BluetoothDevice::GattConnectionCallback connection_callback_;
+
+  base::WeakPtrFactory<BluetoothLowEnergyConnectionFinder> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(BluetoothLowEnergyConnectionFinder);
+};
+
+}  // namespace proximity_auth
+
+#endif  // COMPONENTS_PROXIMITY_AUTH_BLUETOOTH_CONNECTION_FINDER_H