// helper macros for creating unique variable names
#define CONCAT_IMPL(x, y) x##y
#define CONCAT(x, y) CONCAT_IMPL(x, y)
#define delay_us(us) delay_us_INTERNAL(__COUNTER__, us)

// forward declaration so the macro can reference the class
class delayMicrosec;

// this macro instantiates a static delayMicrosec() object per call site
// identified by __COUNTER__ so each use of delay_us() has its own timer 
#define delay_us_INTERNAL(n, us) \
  static delayMicrosec CONCAT(delay_us_, n); \
  CONCAT(delay_us_, n).wait(us)

// non-blocking delayMicroseconds()
class delayMicrosec {
  private:
    esp_timer_handle_t timer;
    TaskHandle_t task;
  public:
    delayMicrosec() : timer(nullptr), task(nullptr) {}
    void wait(uint32_t us) {
      task = xTaskGetCurrentTaskHandle();
      if (!timer) {
        esp_timer_create_args_t args = {
          .callback = [](void* arg) {
            delayMicrosec* self = static_cast<delayMicrosec*>(arg);
            BaseType_t xHigherPriorityTaskWoken = pdFALSE;
            vTaskNotifyGiveFromISR(self->task, &xHigherPriorityTaskWoken);
            if (xHigherPriorityTaskWoken) {
              portYIELD_FROM_ISR();
            }
          },
          .arg = this,
          .dispatch_method = ESP_TIMER_TASK,
          .name = "delay_us_timer"
        };
        esp_timer_create(&args, &timer);
      }
      esp_timer_start_once(timer, us);
      ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
    }
};