#include <psemek/pcg/blur.hpp>

#include <cmath>
#include <vector>

namespace psemek::pcg
{

	static std::vector<float> gauss_coeffs(int size, float sigma)
	{
		std::vector<float> res(2 * size + 1);
		float sum = 0.f;
		for (int i = -size; i <= size; ++i)
		{
			float x = (i / sigma);
			res[i + size] = std::exp(- x * x);
			sum += res[i + size];
		}
		for (auto & c : res)
			c /= sum;
		return res;
	}

	gfx::basic_pixmap<float> blur(gfx::basic_pixmap<float> const & p, int size, float sigma, seamless_tag)
	{
		gfx::basic_pixmap<float> res({p.width(), p.height()}, 0.f);

		auto c = gauss_coeffs(size, sigma);

		for (int y = 0; y < p.height(); ++y)
		{
			for (int x = 0; x < p.width(); ++x)
			{
				for (int j = - size; j <= size; ++j)
				{
					for (int i = - size; i <= size; ++i)
					{
						int ix = (x + i);
						while (ix < 0) ix += p.width();
						if (ix >= p.width()) ix = ix % p.width();

						int iy = (y + j);
						while (iy < 0) iy += p.height();
						if (iy >= p.height()) iy = iy % p.height();

						res(x, y) += p(ix, iy) * c[i + size] * c[j + size];
					}
				}
			}
		}

		return res;
	}

}