// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
// Copyright Amir Hassan (kallaballa) <amir@viel-zu.org>

#include <opencv2/v4d/v4d.hpp>

using std::cerr;
using std::endl;

constexpr long unsigned int WIDTH = 1280;
constexpr long unsigned int HEIGHT = 720;
constexpr bool OFFSCREEN = false;
const unsigned long DIAG = hypot(double(WIDTH), double(HEIGHT));

#ifndef __EMSCRIPTEN__
constexpr double FPS = 60;
constexpr const char* OUTPUT_FILENAME = "shader-demo.mkv";
#endif

cv::Ptr<cv::v4d::V4D> window;

int glow_kernel_size = std::max(int(DIAG / 200 % 2 == 0 ? DIAG / 200 + 1 : DIAG / 200), 1);

/** mandelbrot control parameters **/
// Red, green, blue and alpha. All from 0.0f to 1.0f
nanogui::Color base_color_val(0.2f, 0.6f, 1.0f, 1.0f);
// Keep alpha separate for the GUI
float alpha = 1.0f; //0.0-1.0
//contrast boost
int contrast_boost = 15; //0.0-255
int max_iterations = 500;
float center_x = -0.119609;
float center_y = 0.13262;
float zoom_factor = 1.0;
float zoom = 1.0;
float zoom_incr = 0.99;
long iterations = 0;
bool manual_navigation = false;

/** GL uniform handles **/
GLint base_color_hdl;
GLint contrast_boost_hdl;
GLint max_iterations_hdl;
GLint center_x_hdl;
GLint center_y_hdl;
GLint zoom_hdl;

/** shader and program handle **/
GLuint shader_program_hdl;

//vertex array
GLuint VAO;
GLuint VBO, EBO;

// vertex position, color
float vertices[] = {
//    x      y      z
        -1.0f, -1.0f, -0.0f, 1.0f, 1.0f, -0.0f, -1.0f, 1.0f, -0.0f, 1.0f, -1.0f, -0.0f };

unsigned int indices[] = {
//  2---,1
//  | .' |
//  0'---3
        0, 1, 2, 0, 3, 1 };

static void load_buffer_data() {

    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);

    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*) 0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

//mandelbrot shader code adapted from my own project: https://github.com/kallaballa/FractalDive#after
static void load_shader() {
#if !defined(__EMSCRIPTEN__) && !defined(OPENCV_V4D_USE_ES3)
    const string shaderVersion = "330";
#else
    const string shaderVersion = "300 es";
#endif

    const string vert =
            "    #version " + shaderVersion
                    + R"(
    in vec4 position;
    
    void main()
    {
        gl_Position = vec4(position.xyz, 1.0);
    })";

    const string frag =
            "    #version " + shaderVersion
                    + R"(
    precision lowp float;

    out vec4 outColor;
    
    uniform vec4 base_color;
    uniform int contrast_boost;
    uniform int max_iterations;
    uniform float zoom;
    uniform float center_x;
    uniform float center_y;

    int get_iterations()
    {
        float pointr = (((gl_FragCoord.x / 720.0f) - 0.5f) * zoom + center_x) * 5.0f;
        float pointi = (((gl_FragCoord.y / 720.0f) - 0.5f) * zoom + center_y) * 5.0f;
        const float four = 4.0f;

        int iterations = 0;
        float zi = 0.0f;
        float zr = 0.0f;
        float zrsqr = 0.0f;
        float zisqr = 0.0f;

        while (iterations < max_iterations && zrsqr + zisqr < four) {
           //equals following line as a consequence of binomial expansion: zi = (((zr + zi)*(zr + zi)) - zrsqr) - zisqr
            zi = (zr + zr) * zi;

            zi += pointi;
            zr = (zrsqr - zisqr) + pointr;
    
            zrsqr = zr * zr;
            zisqr = zi * zi;
            ++iterations;
        }
        return iterations;
    }
     
    void determine_color()
    {
        int iter = get_iterations();
        if (iter < max_iterations) {   
            float iterations = float(iter) / float(max_iterations);
            //convert to float
            float cb = float(contrast_boost);
    
            outColor = vec4(base_color[0] * iterations * cb, base_color[1] * iterations * cb, base_color[2] * iterations * cb, base_color[3]);
        } else {
//            gl_FragDepth = -1.0;
            outColor = vec4(0,0,0,0);
        }
    }

    void main()
    {
        determine_color();
    })";

    cerr << "##### Vertex Shader #####" << endl;
    cerr << vert << endl;

    cerr << "##### Fragment Shader #####" << endl;
    cerr << frag << endl;

    shader_program_hdl = cv::v4d::initShader(vert.c_str(), frag.c_str(), "fragColor");
}

static float easeInOutQuint(float x) {
    return x < 0.5f ? 16.0f * x * x * x * x * x : 1.0f - std::pow(-2.0f * x + 2.0f, 5.0f) / 2.0f;
}

static void init_scene(const cv::Size& sz) {
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    load_shader();
    load_buffer_data();

    base_color_hdl = glGetUniformLocation(shader_program_hdl, "base_color");
    contrast_boost_hdl = glGetUniformLocation(shader_program_hdl, "contrast_boost");
    max_iterations_hdl = glGetUniformLocation(shader_program_hdl, "max_iterations");
    zoom_hdl = glGetUniformLocation(shader_program_hdl, "zoom");
    center_x_hdl = glGetUniformLocation(shader_program_hdl, "center_x");
    center_y_hdl = glGetUniformLocation(shader_program_hdl, "center_y");

    glViewport(0, 0, sz.width, sz.height);
}

static void render_scene() {
    if (zoom >= 1) {
        zoom_incr = -0.01;
        iterations = 0;
    } else if (zoom < 2.5e-06) {
        zoom_incr = +0.01;
        iterations = 0;
    }

    glUseProgram(shader_program_hdl);
    glUniform4f(base_color_hdl, base_color_val[0], base_color_val[1], base_color_val[2], alpha);
    glUniform1i(contrast_boost_hdl, contrast_boost);
    glUniform1i(max_iterations_hdl, max_iterations);
    glUniform1f(center_y_hdl, center_y);
    glUniform1f(center_x_hdl, center_x);
    if (!manual_navigation) {
        zoom += zoom_incr;
        glUniform1f(zoom_hdl, easeInOutQuint(zoom));
    } else {
        zoom = 1.0 / pow(zoom_factor, 5.0f);
        glUniform1f(zoom_hdl, zoom);
    }
    glBindVertexArray(VAO);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
}

#ifndef __EMSCRIPTEN__
static void glow_effect(const cv::UMat& src, cv::UMat& dst, const int ksize) {
    static cv::UMat resize;
    static cv::UMat blur;
    static cv::UMat dst16;

    cv::bitwise_not(src, dst);

    //Resize for some extra performance
    cv::resize(dst, resize, cv::Size(), 0.5, 0.5);
    //Cheap blur
    cv::boxFilter(resize, resize, -1, cv::Size(ksize, ksize), cv::Point(-1, -1), true,
            cv::BORDER_REPLICATE);
    //Back to original size
    cv::resize(resize, blur, src.size());

    //Multiply the src image with a blurred version of itself
    cv::multiply(dst, blur, dst16, 1, CV_16U);
    //Normalize and convert back to CV_8U
    cv::divide(dst16, cv::Scalar::all(255.0), dst, 1, CV_8U);

    cv::bitwise_not(dst, dst);
}
#endif

static void setup_gui(cv::Ptr<cv::v4d::V4D> v4dMain) {
    v4dMain->nanogui([](cv::v4d::FormHelper& form) {
        form.makeDialog(5, 30, "Fractal");

        form.makeGroup("Navigation");
        form.makeFormVariable("Iterations", max_iterations, 3, 1000000, true, "","How deeply to calculate the fractal." );
        auto* cxVar = form.makeFormVariable("X", center_x, -1.0f, 1.0f, true, "",
                "The x location from -1.0 to 1.0");
        cxVar->number_format("%.7g");
        cxVar->set_value_increment(0.0000001);
        cxVar->set_callback([&, cxVar](const float& value) {
            manual_navigation = true;
            cxVar->set_value(value);
            center_x = value;
        });

        auto* cyVar = form.makeFormVariable("Y", center_y, -1.0f, 1.0f, true, "",
                "The y location from -1.0 to 1.0");
        cyVar->number_format("%.7g");
        cyVar->set_value_increment(0.0000001);
        cyVar->set_callback([&, cyVar](const float& value) {
            manual_navigation = true;
            cyVar->set_value(value);
            center_y = value;
        });

        auto* czVar = form.makeFormVariable("Zoom", zoom_factor, 1.0f, 1000000.0f, true, "",
                "How much to zoom in on the fractal");
        czVar->set_callback([&, czVar](const float& value) {
            manual_navigation = true;
            czVar->set_value(value);
            zoom_factor = value;
        });

#ifndef __EMSCRIPTEN__
        form.makeGroup("Glow");
        auto* kernelSize = form.makeFormVariable("Kernel Size", glow_kernel_size, 1, 127, true, "",
                "Intensity of glow defined by kernel size");
        kernelSize->set_callback([=](const int& k) {
            static int lastKernelSize = glow_kernel_size;

            if (k == lastKernelSize)
                return;

            if (k <= lastKernelSize) {
                glow_kernel_size = std::max(int(k % 2 == 0 ? k - 1 : k), 1);
            } else if (k > lastKernelSize)
                glow_kernel_size = std::max(int(k % 2 == 0 ? k + 1 : k), 1);

            lastKernelSize = k;
            kernelSize->set_value(glow_kernel_size);
        });
#endif
        form.makeGroup("Color");
        form.makeColorPicker("Color", base_color_val, "The base color of the fractal visualization",
                [&](const nanogui::Color& c) {
                    base_color_val[0] = c[0];
                    base_color_val[1] = c[1];
                    base_color_val[2] = c[2];
                });
        form.makeFormVariable("Alpha", alpha, 0.0f, 1.0f, true, "",
                "The opacity of the fractal visualization");
        form.makeFormVariable("Contrast boost", contrast_boost, 1, 255, true, "",
                "Boost contrast by this factor");
    });
}

static bool iteration() {
    if(!window->capture())
        return false;

    //Render using OpenGL
    window->gl(render_scene);

//To slow for WASM but works
#ifndef __EMSCRIPTEN__
    //Aquire the frame buffer for use by OpenCL
    window->fb([](cv::UMat& frameBuffer) {
        //Glow effect (OpenCL)
        glow_effect(frameBuffer, frameBuffer, glow_kernel_size);
    });
#endif

    window->write();

    ++iterations;
    //If onscreen rendering is enabled it displays the framebuffer in the native window. Returns false if the window was closed.
    return window->display();
}

#ifndef __EMSCRIPTEN__
int main(int argc, char** argv) {
    if (argc != 2) {
        cerr << "Usage: shader-demo <video-file>" << endl;
        exit(1);
    }
#else
int main() {
#endif
    try {
        using namespace cv::v4d;
        window = V4D::make(cv::Size(WIDTH, HEIGHT), cv::Size(), "Shader Demo", OFFSCREEN);

        if (!OFFSCREEN) {
            setup_gui(window);
        }

        window->printSystemInfo();

        window->gl(init_scene);

#ifndef __EMSCRIPTEN__
        Source src = makeCaptureSource(argv[1]);
        window->setSource(src);
        Sink sink = makeWriterSink(OUTPUT_FILENAME, cv::VideoWriter::fourcc('V', 'P', '9', '0'),
                FPS, cv::Size(WIDTH, HEIGHT));
        window->setSink(sink);
#else
        Source src = makeCaptureSource(WIDTH, HEIGHT, window);
        window->setSource(src);
#endif

        window->run(iteration);
    } catch (std::exception& ex) {
        cerr << "Exception: " << ex.what() << endl;
    }
    return 0;
}