Implement receiver HID++ connect/disconnect events

Many changes were made here but that was the biggest one.

There's currently a bug where std::system_error: Broken pipe is thrown
after launching the daemon with a receiver connector.

A workaround for this bug is to simply shake the mouse while starting
the daemon. I will investigate this soon.

src/logid/backend/dj/ReceiverMonitor.cpp

@@ -1,30 +1,70 @@
 #include "ReceiverMonitor.h"
 
 #include <utility>
+#include <cassert>
 
 using namespace logid::backend::dj;
 
-ReceiverMonitor::ReceiverMonitor(std::string path) : _reciever (std::move(path))
+ReceiverMonitor::ReceiverMonitor(std::string path) : _receiver (
+        std::make_shared<Receiver>(std::move(path)))
 {
+    assert(_receiver->hidppEventHandlers().find("RECVMON") ==
+        _receiver->hidppEventHandlers().end());
+    assert(_receiver->djEventHandlers().find("RECVMON") ==
+           _receiver->djEventHandlers().end());
+
     Receiver::notification_flags notification_flags{
         true,
         true,
         true};
-   _reciever.enableHidppNotifications(notification_flags);
+   _receiver->enableHidppNotifications(notification_flags);
 }
 
 void ReceiverMonitor::run()
 {
-    _reciever.listen();
+    _receiver->listen();
+
+    if(_receiver->hidppEventHandlers().find("RECVMON") ==
+           _receiver->hidppEventHandlers().end())
+    {
+        std::shared_ptr<hidpp::EventHandler> eventHandler =
+                std::make_shared<hidpp::EventHandler>();
+        eventHandler->condition = [](hidpp::Report &report) -> bool {
+            return (report.subId() == Receiver::DeviceConnection ||
+                    report.subId() == Receiver::DeviceDisconnection);
+        };
+
+        eventHandler->callback = [this](hidpp::Report &report) -> void {
+            /* Running in a new thread prevents deadlocks since the
+             * receiver may be enumerating.
+             */
+            std::thread{[this](hidpp::Report report) {
+                if (report.subId() == Receiver::DeviceConnection)
+                    this->addDevice(this->_receiver->deviceConnectionEvent(
+                            report));
+                else if (report.subId() == Receiver::DeviceDisconnection)
+                    this->removeDevice(this->_receiver->
+                            deviceDisconnectionEvent(report));
+            }, report}.detach();
+        };
+
+        _receiver->addHidppEventHandler("RECVMON", eventHandler);
+    }
+
     enumerate();
 }
 
 void ReceiverMonitor::stop()
 {
-    _reciever.stopListening();
+    _receiver->stopListening();
 }
 
 void ReceiverMonitor::enumerate()
 {
-    _reciever.enumerate();
+    _receiver->enumerateHidpp();
+}
+
+std::shared_ptr<Receiver> ReceiverMonitor::receiver() const
+{
+    return _receiver;
 }