feat: add state change events and callbacks (#798)

main/device_state_event.h

@@ -0,0 +1,39 @@
+#ifndef _DEVICE_STATE_EVENT_H_
+#define _DEVICE_STATE_EVENT_H_
+
+#include <esp_event.h>
+#include <functional>
+#include <vector>
+#include <mutex>
+#include "device_state.h"
+
+ESP_EVENT_DECLARE_BASE(XIAOZHI_STATE_EVENTS);
+
+enum {
+    XIAOZHI_STATE_CHANGED_EVENT,
+};
+
+struct device_state_event_data_t {
+    DeviceState previous_state;
+    DeviceState current_state;
+};
+
+class DeviceStateEventManager {
+public:
+    static DeviceStateEventManager& GetInstance();
+    DeviceStateEventManager(const DeviceStateEventManager&) = delete;
+    DeviceStateEventManager& operator=(const DeviceStateEventManager&) = delete;
+
+    void RegisterStateChangeCallback(std::function<void(DeviceState, DeviceState)> callback);
+    void PostStateChangeEvent(DeviceState previous_state, DeviceState current_state);
+    std::vector<std::function<void(DeviceState, DeviceState)>> GetCallbacks();
+
+private:
+    DeviceStateEventManager();
+    ~DeviceStateEventManager();
+
+    std::vector<std::function<void(DeviceState, DeviceState)>> callbacks_;
+    std::mutex mutex_;
+};
+
+#endif // _DEVICE_STATE_EVENT_H_