New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/platform/battery_tracker.cpp

@@ -0,0 +1,69 @@
+#include "platform/battery_tracker.hpp"
+
+#include "platform/platform.hpp"
+
+namespace
+{
+auto const kBatteryTrackingInterval = std::chrono::minutes(10);
+
+bool IsLevelExpired(std::chrono::system_clock::time_point lastRequestTime)
+{
+  return std::chrono::system_clock::now() - lastRequestTime > kBatteryTrackingInterval;
+}
+}  // namespace
+
+namespace platform
+{
+void BatteryLevelTracker::Subscribe(Subscriber * subscriber)
+{
+  m_subscribers.push_back(subscriber);
+
+  if (!IsLevelExpired(m_lastRequestTime))
+    subscriber->OnBatteryLevelReceived(m_lastReceivedLevel);
+
+  if (!m_isTrackingInProgress)
+  {
+    m_isTrackingInProgress = true;
+    RequestBatteryLevel();
+  }
+}
+
+void BatteryLevelTracker::Unsubscribe(Subscriber * subscriber)
+{
+  m_subscribers.erase(std::remove(m_subscribers.begin(), m_subscribers.end(), subscriber),
+                      m_subscribers.end());
+}
+
+void BatteryLevelTracker::UnsubscribeAll()
+{
+  m_subscribers.clear();
+}
+
+void BatteryLevelTracker::RequestBatteryLevel()
+{
+  if (m_subscribers.empty())
+  {
+    m_isTrackingInProgress = false;
+    return;
+  }
+
+  if (IsLevelExpired(m_lastRequestTime))
+  {
+    m_lastReceivedLevel = GetPlatform().GetBatteryLevel();
+    m_lastRequestTime = std::chrono::system_clock::now();
+  }
+
+  for (auto s : m_subscribers)
+  {
+    s->OnBatteryLevelReceived(m_lastReceivedLevel);
+  }
+
+  GetPlatform().RunDelayedTask(Platform::Thread::Background, kBatteryTrackingInterval, [this]
+  {
+    GetPlatform().RunTask(Platform::Thread::Gui, [this]
+    {
+      RequestBatteryLevel();
+    });
+  });
+}
+}  // namespace platform