#include "client/math.hh"

namespace client {
namespace math {

std::optional<glm::vec2> world_to_screen(const glm::vec3& pos,
                                         const glm::mat4& m,
                                         const glm::vec2& window) noexcept {
    // clang-format off
    const float w = m[0][3] * pos.x + m[1][3] * pos.y + m[2][3] * pos.z + m[3][3];

    if (w < 0.0f) {
        return std::nullopt;
    }

    const float inv_w = std::fabs(1.0f / w);

    const float x = window.x * 0.5f + (0.5f * (m[0][0] * pos.x + m[1][0] * pos.y + m[2][0] * pos.z + m[3][0]) * inv_w * window.x + 0.5f);
    const float y = window.y * 0.5f + (0.5f * (m[0][1] * pos.x + m[1][1] * pos.y + m[2][1] * pos.z + m[3][1]) * inv_w * window.y + 0.5f);
    // clang-format on

    return glm::vec2{x, y};
}

} // namespace math
} // namespace client