Audio fsm usability tweaks

- persist the current volume when the screen locks
 - pause playback if headphones are removed

src/audio/audio_fsm.cpp

@@ -50,6 +50,12 @@ std::shared_ptr<IAudioOutput> AudioState::sOutput;
 
 std::optional<database::TrackId> AudioState::sCurrentTrack;
 
+void AudioState::react(const system_fsm::KeyLockChanged& ev) {
+  if (ev.locking && sServices) {
+    sServices->nvs().AmpCurrentVolume(sOutput->GetVolume());
+  }
+}
+
 void AudioState::react(const StepUpVolume& ev) {
   if (sOutput->AdjustVolumeUp()) {
     events::Ui().Dispatch(VolumeChanged{});
@@ -63,10 +69,10 @@ void AudioState::react(const StepDownVolume& ev) {
 }
 
 void AudioState::react(const system_fsm::HasPhonesChanged& ev) {
-  if (ev.falling) {
-    // ESP_LOGI(kTag, "headphones in!");
+  if (ev.has_headphones) {
+    ESP_LOGI(kTag, "headphones in!");
   } else {
-    // ESP_LOGI(kTag, "headphones out!");
+    ESP_LOGI(kTag, "headphones out!");
   }
 }
 
@@ -186,6 +192,12 @@ void Playback::exit() {
   events::Ui().Dispatch(PlaybackFinished{});
 }
 
+void Playback::react(const system_fsm::HasPhonesChanged& ev) {
+  if (!ev.has_headphones) {
+    transit<Standby>();
+  }
+}
+
 void Playback::react(const QueueUpdate& ev) {
   if (!ev.current_changed) {
     return;

src/audio/include/audio_fsm.hpp

@@ -43,11 +43,12 @@ class AudioState : public tinyfsm::Fsm<AudioState> {
 
   void react(const StepUpVolume&);
   void react(const StepDownVolume&);
-  void react(const system_fsm::HasPhonesChanged&);
+  virtual void react(const system_fsm::HasPhonesChanged&);
   void react(const ChangeMaxVolume&);
   void react(const OutputModeChanged&);
 
   virtual void react(const system_fsm::BootComplete&) {}
+  void react(const system_fsm::KeyLockChanged&);
 
   virtual void react(const PlayFile&) {}
   virtual void react(const QueueUpdate&) {}
@@ -97,6 +98,8 @@ class Playback : public AudioState {
   void entry() override;
   void exit() override;
 
+  void react(const system_fsm::HasPhonesChanged&) override;
+
   void react(const PlayFile&) override;
   void react(const QueueUpdate&) override;
   void react(const PlaybackUpdate&) override;

src/system_fsm/include/system_events.hpp

@@ -46,7 +46,7 @@ struct KeyLockChanged : tinyfsm::Event {
   bool locking;
 };
 struct HasPhonesChanged : tinyfsm::Event {
-  bool falling;
+  bool has_headphones;
 };
 
 struct ChargingStatusChanged : tinyfsm::Event {};

src/system_fsm/system_fsm.cpp

@@ -57,10 +57,11 @@ void SystemState::react(const internal::GpioInterrupt&) {
   if (key_lock != prev_key_lock) {
     KeyLockChanged ev{.locking = key_lock};
     events::System().Dispatch(ev);
+    events::Audio().Dispatch(ev);
     events::Ui().Dispatch(ev);
   }
   if (has_headphones != prev_has_headphones) {
-    HasPhonesChanged ev{.falling = prev_has_headphones};
+    HasPhonesChanged ev{.has_headphones = has_headphones};
     events::Audio().Dispatch(ev);
   }
 }