#include <psemek/audio/effect/volume_base.hpp>
#include <psemek/audio/constants.hpp>
#include <psemek/audio/attack.hpp>

#include <cmath>

namespace psemek::audio
{

	volume_base::volume_base(float gain, float attack)
		: gain_{gain}
		, attack_multiplier_{attack_to_multiplier(attack)}
		, real_gain_{gain}
		, last_sample_src_{0.f, 0.f}
		, last_sample_tgt_{0.f, 0.f}
	{}

	float volume_base::attack() const
	{
		return multiplier_to_attack(attack_multiplier_.load());
	}

	float volume_base::attack(float value)
	{
		auto old = attack_multiplier_.exchange(attack_to_multiplier(value));
		return multiplier_to_attack(old);
	}

	void volume_base::apply(float * data, std::size_t sample_count)
	{
		float gain = gain_.load();
		float attack_multiplier = attack_multiplier_.load();

		auto apply_impl = [this](float & target, float & last_src, float & last_tgt)
		{
			auto old = target;
			target = last_tgt + (old - last_src) * real_gain_;
			last_src = old;
			last_tgt = target;
		};

		auto end = data + sample_count;
		for (auto p = data; p < end;)
		{
			apply_impl(*p++, last_sample_src_[0], last_sample_tgt_[0]);
			apply_impl(*p++, last_sample_src_[1], last_sample_tgt_[1]);

			attack_update(real_gain_, gain, attack_multiplier);
		}
	}

}