#include "Perlin.hpp"
#include "Grid.hpp"
#include "Interpolation.hpp"

namespace Math::Perlin {

float ease(float t) {
    return t * t * t * ((6 * t - 15) * t + 10);
}

uint8_t hash(uint8_t x) {
    auto rot = x * 5 % 8;
    return x << rot | x >> (8 - rot);
}

Vector<2> gradient(Vector<2> pos) {
    Vector<2> gradients[] = {
        {1.0f, 1.0f}, {-1.0f, 1.0f},
        {1.0f, -1.0f}, {-1.0f, -1.0f},
    };

    auto x = hash(hash(pos.x()) + pos.y());
    return gradients[x % 4].normalize();
}

float raw(Vector<2> pos) {
    auto cell = grid_cell_for_point(pos);
    auto uv = pos - cell.top_left();

    auto unit = grid_cell_for_point({});
    auto l11 = unit.top_left() - uv;
    auto l21 = unit.top_right() - uv;
    auto l12 = unit.bottom_left() - uv;
    auto l22 = unit.bottom_right() - uv;

    auto g11 = gradient(cell.top_left());
    auto g21 = gradient(cell.top_right());
    auto g12 = gradient(cell.bottom_left());
    auto g22 = gradient(cell.bottom_right());

    auto v = bilinear_interpolation(
        {l11 * g11, l21 * g21, l12 * g12, l22 * g22},
        cell,
        uv.map(ease) + cell.top_left()
    );
    return (v + 1.0f) / 2.0f;
}

Vector<3> gradient(Vector<3> pos) {
    constexpr float e = 0.5773502692;
    static Vector<3> gradients[] = {
        {e, e, e}, {-e, e, e}, {e, -e, e}, {-e, -e, e},
        {e, e, -e}, {-e, e, -e}, {e, -e, -e}, {-e, -e, -e},
    };

    auto x = hash(hash(hash(pos.x()) + pos.y()) + pos.z());
    return gradients[x % 8];
}

float raw(Vector<3> pos) {
    auto cell = cube_cell_for_point(pos);
    auto uv = pos - cell.front_top_left();

    auto unit = cube_cell_for_point({});
    auto l111 = unit.front_top_left() - uv;
    auto l211 = unit.front_top_right() - uv;
    auto l121 = unit.front_bottom_left() - uv;
    auto l221 = unit.front_bottom_right() - uv;
    auto l112 = unit.back_top_left() - uv;
    auto l212 = unit.back_top_right() - uv;
    auto l122 = unit.back_bottom_left() - uv;
    auto l222 = unit.back_bottom_right() - uv;

    auto g111 = gradient(cell.front_top_left());
    auto g211 = gradient(cell.front_top_right());
    auto g121 = gradient(cell.front_bottom_left());
    auto g221 = gradient(cell.front_bottom_right());
    auto g112 = gradient(cell.back_top_left());
    auto g212 = gradient(cell.back_top_right());
    auto g122 = gradient(cell.back_bottom_left());
    auto g222 = gradient(cell.back_bottom_right());

    auto v = trilinear_interpolation(
        {l111 * g111, l211 * g211, l121 * g121, l221 * g221},
        {l112 * g112, l212 * g212, l122 * g122, l222 * g222},
        cell,
        uv.map(ease) + cell.front_top_left()
    );
    return (v + 1.0f) / 2.0f;
}

}