valueproducer.h

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#ifndef SENSESP_SYSTEM_VALUE_PRODUCER_H_
#define SENSESP_SYSTEM_VALUE_PRODUCER_H_
 
#include <ArduinoJson.h>
#include <memory>
 
#include "observable.h"
#include "valueconsumer.h"
 
namespace sensesp {
 
// The Transform class is defined in transforms/transform.h
template <typename C, typename P>
class Transform;

template <typename T>
class ValueProducer : virtual public Observable {
 public:
  ValueProducer() {}
  ValueProducer(const T& initial_value) : output_(initial_value) {}

  virtual const T& get() const { return output_; }

  template <typename VConsumer>
  typename std::enable_if<
    std::is_base_of<ValueConsumer<typename VConsumer::input_type>, VConsumer>::value &&
    std::is_convertible<T, typename VConsumer::input_type>::value,
    std::shared_ptr<VConsumer>
  >::type
  connect_to(std::shared_ptr<VConsumer> consumer) {
    using CInput = typename VConsumer::input_type;
    // Strong reference: the observer lambda owns the shared_ptr, keeping the
    // consumer alive. This assumes acyclic signal chains (no A→B→A loops).
    this->attach([this, consumer]() {
      consumer->set(static_cast<CInput>(this->get()));
    });
    return consumer;
  }
 
  template <typename VConsumer>
  typename std::enable_if<
    std::is_base_of<ValueConsumer<typename VConsumer::input_type>, VConsumer>::value &&
    std::is_convertible<T, typename VConsumer::input_type>::value,
    VConsumer*
  >::type
  connect_to(VConsumer* consumer) {
    using CInput = typename VConsumer::input_type;
    this->attach([this, consumer]() {
      consumer->set(static_cast<CInput>(this->get()));
    });
    return consumer;
  }
 
  template <typename VConsumer>
  typename std::enable_if<
    std::is_base_of<ValueConsumer<typename VConsumer::input_type>, VConsumer>::value &&
    std::is_convertible<T, typename VConsumer::input_type>::value,
    VConsumer*
  >::type
  connect_to(VConsumer& consumer) {
    return connect_to(&consumer);
  }
 
  /*
   * Set a new output value and notify consumers about it
   */
  void emit(const T& new_value) {
    this->output_ = new_value;
    Observable::notify();
  }
 
 protected:
  T output_;
};
 
typedef ValueProducer<float> FloatProducer;
typedef ValueProducer<int> IntProducer;
typedef ValueProducer<bool> BoolProducer;
typedef ValueProducer<String> StringProducer;
 
}  // namespace sensesp
 
#endif  // SENSESP_SYSTEM_VALUE_PRODUCER_H_