/*
 * GLFW_INCLUDE_VULKAN will include its own definitions and
 * automatically load the Vulkan header with it.
 *
 * The stdexcept and iostream headers are included for reporting and
 * propagating errors. The cstdlib header provides the EXIT_SUCCESS
 * and EXIT_FAILURE macros.
 */

#define GLFW_INCLUDE_VULKAN
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdexcept>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <optional>
#include <set>

const uint32_t WIDTH = 800;
const uint32_t HEIGHT = 600;

/*
 * All of the useful standard validation is bundled into a layer
 * included in the SDK that is known as VK_LAYER_KHRONOS_validation.
 */

const std::vector<const char*> validationLayers = {
    "VK_LAYER_KHRONOS_validation"
};

/*
 * The NDEBUG macro is part of the C++ standard and means "not debug".
 * Base that value on whether the program is being compiled in debug
 * mode or not.
 */

#ifdef NDEBUG
const bool enableValidationLayers = false;
#else
const bool enableValidationLayers = true;
#endif

/*
 * Proxy function that handles looks up the address of
 * VkDebugUtilsMessengerEXT using vkGetInstanceProcAddr.
 */

VkResult CreateDebugUtilsMessengerEXT(VkInstance instance, const VkDebugUtilsMessengerCreateInfoEXT* pCreateInfo, const VkAllocationCallbacks* pAllocator, VkDebugUtilsMessengerEXT* pDebugMessenger) {
    auto func = (PFN_vkCreateDebugUtilsMessengerEXT) vkGetInstanceProcAddr(instance, "vkCreateDebugUtilsMessengerEXT");
    if (func != nullptr) {
        return func(instance, pCreateInfo, pAllocator, pDebugMessenger);
    } else {
        return VK_ERROR_EXTENSION_NOT_PRESENT;
    }
}

/*
 * Proxy function that handles cleaning up the
 * VkDebugUtilsMessengerEXT object.
 */

void DestroyDebugUtilsMessengerEXT(VkInstance instance, VkDebugUtilsMessengerEXT debugMessenger, const VkAllocationCallbacks* pAllocator) {
    auto func = (PFN_vkDestroyDebugUtilsMessengerEXT) vkGetInstanceProcAddr(instance, "vkDestroyDebugUtilsMessengerEXT");
    if (func != nullptr) {
        func(instance, debugMessenger, pAllocator);
    }
}

/*
 * It has been briefly touched upon before that almost every operation in Vulkan,
 * anything from drawing to uploading textures, requires commands to be submitted
 * to a queue. There are different types of queues that originate from different
 * queue families and each family of queues allows only a subset of commands.
 * For example, there could be a queue family that only allows processing of compute
 * commands or one that only allows memory transfer related commands.
 * We need to check which queue families are supported by the device and which
 * one of these supports the commands that we want to use. For that purpose we'll
 * add a new function findQueueFamilies that looks for all the queue families
 * we need.
 */

struct QueueFamilyIndices {

    /*
     * std::optional is a wrapper that contains no value until you assign something
     * to it. At any point you can query if it contains a value or not by calling
     * its has_value() member function.
     */

    std::optional<uint32_t> graphicsFamily;
    std::optional<uint32_t> presentFamily;

    bool isComplete() {
        return graphicsFamily.has_value() && presentFamily.has_value();
    }
};

/*
 * The program itself is wrapped into a class where we'll store the
 * Vulkan objects as private class members and add functions to
 * initiate each of them, which will be called from the initVulkan
 * function.
 */

class Application {
public:
    void run() {
        initWindow();
        initVulkan();
        mainLoop();
        cleanup();
    }

private:
    GLFWwindow* window; // Member to store a reference to it and initialize the window

    VkInstance instance; // Data member to hold the handle to the instance
    VkDebugUtilsMessengerEXT debugMessenger;
    VkSurfaceKHR surface;

    VkPhysicalDevice physicalDevice = VK_NULL_HANDLE;
    VkDevice device;

    VkQueue graphicsQueue; // Class member to store a handle to the graphics queue
    VkQueue presentQueue;

    void initWindow() {
        glfwInit();
        glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
        glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);

        window = glfwCreateWindow(
            WIDTH,
            HEIGHT,
            "@@@ Window Name",
            nullptr,
            nullptr
        );
    }

    void initVulkan() {
        createInstance();
        setupDebugMessenger();
        createSurface();
        pickPhysicalDevice();
        createLogicalDevice();
    }

    void mainLoop() {
        while (!glfwWindowShouldClose(window)) {
            glfwPollEvents();
        }
    }

    /*
     * Once the window is closed and mainLoop returns,
     * we'll make sure to deallocate the resources.
     */

    void cleanup() {
        vkDestroyDevice(device, nullptr); // Destroy logical device

        if (enableValidationLayers) {
            DestroyDebugUtilsMessengerEXT(instance, debugMessenger, nullptr);
        }

        vkDestroySurfaceKHR(instance, surface, nullptr);
        vkDestroyInstance(instance, nullptr);

        glfwDestroyWindow(window);
        glfwTerminate();
    }

    void createInstance() {
        if (enableValidationLayers && !checkValidationLayerSupport()) {
            throw std::runtime_error("validation layers requested, but not available!");
        }

        /*
         * Struct with some information about our application. This data is technically
         * optional, but it may provide some useful information to the driver in order
         * to optimize our specific application (e.g. because it uses a well-known
         * graphics engine with certain special behavior).
         */

        VkApplicationInfo gameInfo{};
        gameInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
        gameInfo.pApplicationName = "@@@ Application Name";
        gameInfo.applicationVersion = VK_MAKE_VERSION(1, 0, 0);
        gameInfo.pEngineName = "No Engine";
        gameInfo.engineVersion = VK_MAKE_VERSION(1, 0, 0);
        gameInfo.apiVersion = VK_API_VERSION_1_0;

        VkInstanceCreateInfo createInfo{};
        createInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
        createInfo.pApplicationInfo = &gameInfo;

        auto extensions = getRequiredExtensions();
        createInfo.enabledExtensionCount = static_cast<uint32_t>(extensions.size());
        createInfo.ppEnabledExtensionNames = extensions.data();

        /*
         * If the check was successful then vkCreateInstance should not ever return
         * a VK_ERROR_LAYER_NOT_PRESENT error.
         */

        VkDebugUtilsMessengerCreateInfoEXT debugCreateInfo{};
        if (enableValidationLayers) {
            createInfo.enabledLayerCount = static_cast<uint32_t>(validationLayers.size());
            createInfo.ppEnabledLayerNames = validationLayers.data();

            populateDebugMessengerCreateInfo(debugCreateInfo);
            createInfo.pNext = (VkDebugUtilsMessengerCreateInfoEXT*) &debugCreateInfo;
        } else {
            createInfo.enabledLayerCount = 0;
            createInfo.pNext = nullptr;
        }

        if (vkCreateInstance(&createInfo, nullptr, &instance) != VK_SUCCESS) {
            throw std::runtime_error("failed to create instance!");
        }
    }

    /*
     * This struct should be passed to the vkCreateDebugUtilsMessengerEXT
     * function to create the VkDebugUtilsMessengerEXT object. Unfortunately,
     * because this function is an extension function, it is not automatically
     * loaded. We use a proxy function, VkResult.
     */

    void populateDebugMessengerCreateInfo(VkDebugUtilsMessengerCreateInfoEXT& createInfo) {
        createInfo = {};
        createInfo.sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT;
        createInfo.messageSeverity = VK_DEBUG_UTILS_MESSAGE_SEVERITY_VERBOSE_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT;
        createInfo.messageType = VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT;
        createInfo.pfnUserCallback = debugCallback;
    }

    void setupDebugMessenger() {
        if (!enableValidationLayers) return;

        VkDebugUtilsMessengerCreateInfoEXT createInfo;
        populateDebugMessengerCreateInfo(createInfo);

        if (CreateDebugUtilsMessengerEXT(instance, &createInfo, nullptr, &debugMessenger) != VK_SUCCESS) {
            throw std::runtime_error("failed to set up debug messenger!");
        }
    }

    void createSurface() {
        if (glfwCreateWindowSurface(instance, window, nullptr, &surface) != VK_SUCCESS) {
            throw std::runtime_error("failed to create window surface!");
        }
    }

    /*
     * Select a physical device
     */

    void pickPhysicalDevice() {
        uint32_t deviceCount = 0;
        vkEnumeratePhysicalDevices(instance, &deviceCount, nullptr);

        if (deviceCount == 0) {
            throw std::runtime_error("failed to find GPUs with Vulkan support!");
        }

        std::vector<VkPhysicalDevice> devices(deviceCount);
        vkEnumeratePhysicalDevices(instance, &deviceCount, devices.data());

        for (const auto& device : devices) {
            if (isDeviceSuitable(device)) {
                physicalDevice = device;
                break;
            }
        }

        /*
         * Check if any of the physical devices meet the requirements
         */

        if (physicalDevice == VK_NULL_HANDLE) {
            throw std::runtime_error("failed to find a suitable GPU!");
        }
    }
    
    /*
     * Check if any of the physical devices meet the requirements
     */

    void createLogicalDevice() {
        QueueFamilyIndices indices = findQueueFamilies(physicalDevice);

        std::vector<VkDeviceQueueCreateInfo> queueCreateInfos;
        std::set<uint32_t> uniqueQueueFamilies = {indices.graphicsFamily.value(), indices.presentFamily.value()};

        float queuePriority = 1.0f;
        for (uint32_t queueFamily : uniqueQueueFamilies) {
            VkDeviceQueueCreateInfo queueCreateInfo{};
            queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
            queueCreateInfo.queueFamilyIndex = queueFamily;
            queueCreateInfo.queueCount = 1;
            queueCreateInfo.pQueuePriorities = &queuePriority;
            queueCreateInfos.push_back(queueCreateInfo);
        }

        VkPhysicalDeviceFeatures deviceFeatures{};

        VkDeviceCreateInfo createInfo{};
        createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
        createInfo.queueCreateInfoCount = static_cast<uint32_t>(queueCreateInfos.size());
        createInfo.pQueueCreateInfos = queueCreateInfos.data();
        createInfo.pEnabledFeatures = &deviceFeatures;
        createInfo.enabledExtensionCount = 0;

        if (enableValidationLayers) {
            createInfo.enabledLayerCount = static_cast<uint32_t>(validationLayers.size());
            createInfo.ppEnabledLayerNames = validationLayers.data();
        } else {
            createInfo.enabledLayerCount = 0;
        }

        if (vkCreateDevice(physicalDevice, &createInfo, nullptr, &device) != VK_SUCCESS) {
            throw std::runtime_error("failed to create logical device!");
        }

        vkGetDeviceQueue(device, indices.graphicsFamily.value(), 0, &graphicsQueue);
        vkGetDeviceQueue(device, indices.presentFamily.value(), 0, &presentQueue);
    }

    bool isDeviceSuitable(VkPhysicalDevice device) {
        QueueFamilyIndices indices = findQueueFamilies(device);

        return indices.isComplete();
    }

    QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
        QueueFamilyIndices indices;

        uint32_t queueFamilyCount = 0;
        vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, nullptr);

        std::vector<VkQueueFamilyProperties> queueFamilies(queueFamilyCount);
        vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, queueFamilies.data());

        int i = 0;
        for (const auto& queueFamily : queueFamilies) {
            if (queueFamily.queueFlags & VK_QUEUE_GRAPHICS_BIT) {
                indices.graphicsFamily = i;
            }

            VkBool32 presentSupport = false;
            vkGetPhysicalDeviceSurfaceSupportKHR(device, i, surface, &presentSupport);

            if (presentSupport) {
                indices.presentFamily = i;
            }

            if (indices.isComplete()) {
                break;
            }

            i++;
        }

        return indices;
    }

    std::vector<const char*> getRequiredExtensions() {

        /*
         * Vulkan is a platform agnostic API, which means that you need
         * an extension to interface with the window system. GLFW has a
         * handy built-in function that returns the extension(s) it needs
         * to do that.
         */

        uint32_t glfwExtensionCount = 0;
        const char** glfwExtensions;
        glfwExtensions = glfwGetRequiredInstanceExtensions(&glfwExtensionCount);

        std::vector<const char*> extensions(glfwExtensions, glfwExtensions + glfwExtensionCount);

        if (enableValidationLayers) {
            extensions.push_back(VK_EXT_DEBUG_UTILS_EXTENSION_NAME);
        }

        return extensions;
    }

    /*
     * checkValidationLayerSupport checks if all of the requested layers
     * are available. First list all of the available layers using the
     * vkEnumerateInstanceLayerProperties function.
     */

    bool checkValidationLayerSupport() {
        uint32_t layerCount;
        vkEnumerateInstanceLayerProperties(&layerCount, nullptr);

        std::vector<VkLayerProperties> availableLayers(layerCount);
        vkEnumerateInstanceLayerProperties(&layerCount, availableLayers.data());

        /*
         * Check if all of the layers in validationLayers exist in the
         * availableLayers list.
         */

        for (const char* layerName : validationLayers) {
            bool layerFound = false;

            for (const auto& layerProperties : availableLayers) {
                if (strcmp(layerName, layerProperties.layerName) == 0) {
                    layerFound = true;
                    break;
                }
            }

            if (!layerFound) {
                return false;
            }
        }

        return true;
    }

    static VKAPI_ATTR VkBool32 VKAPI_CALL debugCallback(VkDebugUtilsMessageSeverityFlagBitsEXT messageSeverity, VkDebugUtilsMessageTypeFlagsEXT messageType, const VkDebugUtilsMessengerCallbackDataEXT* pCallbackData, void* pUserData) {
        std::cerr << "validation layer: " << pCallbackData->pMessage << std::endl;

        return VK_FALSE;
    }
};

/*
 * Enter the main loop to start rendering frames. We'll fill in
 * the mainLoop function to include a loop that iterates until
 * the window is closed.
 */

int main() {
    Application game;

    try {
        game.run();
    } catch (const std::exception& e) {
        std::cerr << e.what() << std::endl;
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}