#include "Clouds.hpp"
#include "../Math/MVP.hpp"
#include "../Math/Perlin.hpp"
#include "../Math/AABB.hpp"
#include "../GFX/Util/Primitives.hpp"
#include "../GFX/Util/MeshBuilder.hpp"
#include <GL/glew.h>
#include <array>

namespace MC::World {

Clouds::Clouds(Real ascept, Real fov, Real near, Real far, Vector<3, F32> sky_color, Vector<3, F32> sun_direction)
    : m_program(
    {GFX::Shading::Shader::Type::Vertex, vertex},
    {GFX::Shading::Shader::Type::Fragment, fragment}
    ),
    m_mesh(GFX::Binder::load(create_mesh(create_cloud_matrix()))),
    m_model_uniform(), m_view_uniform(), m_projection_uniform() {
    m_program.bind();

    m_model_uniform = m_program.uniform("model_matrix");
    m_view_uniform = m_program.uniform("view_matrix");
    m_projection_uniform = m_program.uniform("projection_matrix");
    auto sky_color_uniform = m_program.uniform("sky_color");
    auto sun_direction_uniform = m_program.uniform("sun_direction");

    m_model_uniform.set(Math::MVP::model<F32>({}, {}, {}));
    m_view_uniform.set(Math::MVP::view<F32>({}, {}));
    m_projection_uniform.set(Math::MVP::perspective_projection<F32>(ascept, fov, near, far));
    sky_color_uniform.set(sky_color);
    sun_direction_uniform.set(sun_direction);

    m_program.unbind();
}

void Clouds::update(U64 time) {
    m_x_offset += time / 5000.0;
}

void Clouds::render(const GFX::Camera& camera) const {
    auto position = camera.position();

    I32 center_x = std::round((position.x() - m_x_offset) / TileSize);
    I32 center_y = std::round(position.z() / TileSize);

    for (Int x = -1; x <= 1; x++) {
        for (Int y = -1; y <= 1; y++) {
            render_single_instance(camera, center_x + x, center_y + y);
        }
    }
}

void Clouds::render_single_instance(const GFX::Camera& camera, Int x, Int y) const {
    Vector<3> position{TileSize * x + m_x_offset, Height, TileSize * y};

    m_program.bind();

    m_view_uniform.set(Math::MVP::view<F32>(camera.position(), camera.angles()));
    m_model_uniform.set(Math::MVP::model<F32>(position, Vector<3>{Scale}, {}));

    m_mesh.bind();
    glDrawElements(GL_TRIANGLES, m_mesh.size(), GL_UNSIGNED_INT, nullptr);
    m_mesh.unbind();

    m_program.unbind();
}

Clouds::CloudMatrix Clouds::create_cloud_matrix() {
    Math::Perlin::Noise<2> noise{};

    CloudMatrix clouds{false};
    for (Int x = 1; x < CloudMatrixSize; x++) {
        for (Int y = 1; y < CloudMatrixSize; y++) {
            if (noise.at({x, y * 2}) > 0.55) {
                clouds(x, y) = true;
            }
        }
    }
    return clouds;
}

GFX::Mesh Clouds::create_mesh(const CloudMatrix& cloud_matrix) {
    GFX::Util::MeshBuilder<Vector<3, F32>> builder{};

    for (Int x = 0; x < CloudMatrixSize; x++) {
        for (Int y = 0; y < CloudMatrixSize; y++) {
            if (!cloud_matrix(x, y)) continue;

            auto is_occupied = [&](Int xn, Int yn) {
                if (xn < 0 || xn >= CloudMatrixSize || yn < 0 || yn >= CloudMatrixSize) return false;
                return cloud_matrix(xn, yn);
            };
            std::array<bool, 4> neighbors = {
                is_occupied(x - 1, y), is_occupied(x + 1, y),
                is_occupied(x, y - 1), is_occupied(x, y + 1),
            };

            using FaceSet = GFX::Util::Primitives::FaceSet;
            U8 faces = FaceSet::Top | FaceSet::Bottom;
            if (!neighbors[0]) faces |= FaceSet::Left;
            if (!neighbors[1]) faces |= FaceSet::Right;
            if (!neighbors[2]) faces |= FaceSet::Front;
            if (!neighbors[3]) faces |= FaceSet::Back;

            auto aabb = Math::AABB{{x, 0, y}, {x + 1, 1, y + 1}};
            auto box = GFX::Util::Primitives::box(aabb, (FaceSet::Value)faces);
            builder.primitive(box);
        }
    }

    return builder.mesh();
}

const Char* Clouds::vertex = R"v(
#version 330 core

uniform mat4 model_matrix;
uniform mat4 view_matrix;
uniform mat4 projection_matrix;

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;

out vec3 surface_normal;
out float depth;

void main() {
    vec4 world_position = model_matrix * vec4(position, 1.0);
    vec4 view_position = view_matrix * world_position;
    vec4 clip_position = projection_matrix * view_position;

    gl_Position = clip_position;
    surface_normal = (model_matrix * vec4(normal, 0.0)).xyz;
    depth = clamp((length(view_position) - 200) / 400, 0.0, 1.0);
}
)v";

const Char* Clouds::fragment = R"f(
#version 330 core

uniform vec3 sky_color;
uniform vec3 sun_direction;

in vec3 surface_normal;
in float depth;
out vec4 color;

void main() {
    float brightness = dot(normalize(surface_normal), normalize(-sun_direction));
    vec3 diffuse = vec3(1 - clamp(brightness, -0.3, 0.2));
    vec3 base = vec3(1.0, 1.0, 1.0) * diffuse;

    color = vec4(mix(sky_color, base, 1 - depth), 0.3);
}
)f";

}