#include <psemek/audio/resampler.hpp>
#include <psemek/geom/math.hpp>

#include <vector>

namespace psemek::audio
{

	void resampler::feed(util::span<float const> samples, float ratio)
	{
		result_.clear();

		if (samples.empty())
			return;

		float const delta = 1.f / ratio;

		while (position_ < 0)
		{
			result_.push_back(geom::lerp(last_sample_[0], samples[0], position_frac_));
			result_.push_back(geom::lerp(last_sample_[1], samples[1], position_frac_));
			advance(delta);
		}

		while (2 * position_ + 3 < samples.size())
		{
			result_.push_back(geom::lerp(samples[2 * position_ + 0], samples[2 * position_ + 2], position_frac_));
			result_.push_back(geom::lerp(samples[2 * position_ + 1], samples[2 * position_ + 3], position_frac_));
			advance(delta);
		}

		position_ -= static_cast<int>(samples.size()) / 2;

		last_sample_[0] = samples[samples.size() - 2];
		last_sample_[1] = samples[samples.size() - 1];
	}

	void resampler::advance(float delta)
	{
		position_frac_ += delta;
		auto floor = static_cast<int>(std::floor(position_frac_));
		position_ += floor;
		position_frac_ -= floor;
	}

}