/*
Crafter®.Math
Copyright (C) 2026 Catcrafts®
catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

export module Crafter.Math:Ray;
import :Vector;
import std;

namespace Crafter {
    export template<typename T>
	constexpr T IntersectionTestRayTriangle(Vector<T, 3, 0> vert0, Vector<T, 3, 0> vert1, Vector<T, 3, 0> vert2, Vector<T, 3, 0> rayOrigin, Vector<T, 3, 0> rayDir) {
        constexpr float EPSILON = 0.0000001;
        Vector<T, 3, 0> edge1 = vert1 - vert0;
        Vector<T, 3, 0> edge2 = vert2 - vert0;

        Vector<T, 3, 0> h = Vector<T, 3, 0>::Cross(rayDir, edge2);
        float determinant = Vector<T, 3, 0>::Dot(edge1, h);


        if(determinant < 0) {
            return -1;
        }

        if (determinant > -EPSILON && determinant < EPSILON)  {
            return -1;
        }

        float inverse_determinant = 1.0 / determinant;

        Vector<T, 3, 0> origins_diff_vector = rayOrigin - vert0;
        float u =  Vector<T, 3, 0>::Dot(origins_diff_vector, h) * inverse_determinant;

        if (u < 0.0 || u > 1.0)
        {
            return false;
        }

        Vector<T, 3, 0> q = Vector<T, 3, 0>::Cross(origins_diff_vector, edge1);
        float v = inverse_determinant * Vector<T, 3, 0>::Dot(rayDir, q);

        if (v < 0.0 || u + v > 1.0) {
            return -1;
        }

        return inverse_determinant * Vector<T, 3, 0>::Dot(edge2, q);
    }
}