#ifndef CODE_OBSERVABLE
#define CODE_OBSERVABLE
#include "code/return.h"
#include <vector>
template<class V> class observer_t {
	public:
	virtual void on_change(
		V* value_p
	) = 0;
};
template<class V> class observable_t {
	public:
	enum class error_t {
		none,
		unknown,
		not_observing
	};
	struct configuration_t {
		V* value_m;
	};
	observable_t(
		configuration_t* configuration_p
	) {
		configuration_m = configuration_p;
	}
	void_t<error_t> observe(
		observer_t<V>* observer_p
	) {
		observer_p->on_change(configuration_m->value_m);
		observers_m.push_back(observer_p);
	}
	void_t<error_t> unobserve(
		observer_t<V>* observer_p
	) {
		observable_t::error_t error_l = observable_t::error_t::not_observing;
		for (int i = 0; i < observers_m.size(); i++) {
			if (observers_m[i] == observer_p) {
				observers_m.erase(i);
				error_l = observable_t::error_t::none;
				break;
			}
		}
		void_t<observable_t::error_t> void_l;
		void_l.error_m = error_l;
		return void_l;
	}
	V* get_value() {
		return value_m;
	}
	void_t<error_t> change(
		V* value_p
	) {
		configuration_m->value_m = value_p;
		for (int i = 0; i < observers_m.size(); i++) {
			observer_m = observers_m[i];
			observer_m->on_change(configuration_m->value_m);
		}
		void_t<observable_t::error_t> void_l;
		void_l.error_m = observable_t::error_t::none;
		return void_l;
	}
	private:
	std::vector<observer_t<V>*> observers_m;
	configuration_t* configuration_m;
};
template <class V> class observable_factory_t : public observable_t<V> {
	public:
	return_t<observable_t::error_t, observable_t<V> *> create(
		observable_t::configuration_t configuration_p
	) {
		observable_t<V>* observable_l = new observable_t<V>(
			configuration_p
		);
		return_t<observable_t::error_t, observable_t*> return_l;
		return_l.error_m = observable_t::error_t::none;
		return_l.value_m = observable_l;
		return return_l;
	}
	void_t<observable_t::error_t> dispose(
		observable_t<V>* observable_p
	) {
		delete observable_p;
		void_t<observable_t::error_t> void_l;
		void_l.error_m = observable_t::error_t::none;
		return void_l;
	}
};
#endif