/*
Copyright (c) 2019, Jordan Halase <jordan@halase.me>

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
*/

/* Note: Due to the length of many function and variable names in the
 *       Vulkan API, the line width of any Vulkan-related code here may be
 *       extended from 80 columns to 120 colums to improve readability.
 */

/* The goal of this project is to create an entirely self-contained, embeddable
 * Vulkan renderer. While dynamic linking directly against the system Vulkan
 * loader is safe, it will crash if attempting to run on a system without it
 * installed. By loading the Vulkan library dynamically, the application may
 * gracefully close or even fall back to a different rendering API.
 * Furthermore, Vulkan specifies that using functions retrieved via
 * `vkGetDeviceProcAddr` may actually run faster than if the application were
 * using the Vulkan loader directly due to bypassing the loader terminator.
 *
 * https://vulkan.lunarg.com/doc/sdk/1.0.61.1/windows/LoaderAndLayerInterface.html
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#include <vulkan/vulkan.h>

#if defined(_WIN32)
#include <windows.h>
#include <vulkan/vulkan_win32.h>
#else
#include <X11/Xlib.h>
#include <vulkan/vulkan_xlib.h>
#include "pugl/detail/x11.h"
#endif

#include "test/test_utils.h" // for printEvent()

#include "pugl/pugl.h"
#include "pugl/pugl_stub_backend.h"

#define STB_SPRINTF_IMPLEMENTATION
#include "stb_sprintf.h"

#if defined(__GNUC__)
#define APP_THREAD_LOCAL	__thread
#else
#define APP_THREAD_LOCAL	__declspec(thread)
#endif

/** Vulkan allocation callbacks if we ever decide to use them when debugging.
 *
 * This is put in a macro so we don't have to look for every Vulkan function
 * that uses it.
 */
#define ALLOC_VK	NULL

/** Instance-level Vulkan functions and handle */
struct VulkanAPI {
	void *handle;
	PFN_vkGetInstanceProcAddr			vkGetInstanceProcAddr;
	PFN_vkCreateInstance				vkCreateInstance;
	PFN_vkDestroyInstance				vkDestroyInstance;
	PFN_vkCreateDebugReportCallbackEXT		vkCreateDebugReportCallbackEXT;
	PFN_vkDestroyDebugReportCallbackEXT		vkDestroyDebugReportCallbackEXT;
	PFN_vkDestroySurfaceKHR				vkDestroySurfaceKHR;
	PFN_vkEnumeratePhysicalDevices			vkEnumeratePhysicalDevices;
	PFN_vkGetPhysicalDeviceProperties		vkGetPhysicalDeviceProperties;
	PFN_vkGetPhysicalDeviceQueueFamilyProperties	vkGetPhysicalDeviceQueueFamilyProperties;
	PFN_vkGetPhysicalDeviceSurfaceSupportKHR	vkGetPhysicalDeviceSurfaceSupportKHR;
	PFN_vkGetPhysicalDeviceMemoryProperties		vkGetPhysicalDeviceMemoryProperties;
	PFN_vkEnumerateDeviceExtensionProperties	vkEnumerateDeviceExtensionProperties;
	PFN_vkCreateDevice				vkCreateDevice;
	PFN_vkGetDeviceProcAddr				vkGetDeviceProcAddr;
};

/** Device-level Vulkan functions */
struct VulkanDev {
	PFN_vkDestroyDevice				vkDestroyDevice;
	PFN_vkDeviceWaitIdle				vkDeviceWaitIdle;
};

/** Vulkan application that uses Pugl for windows and events */
struct RenderVulkan {
	struct VulkanAPI *api;
	struct VulkanDev *dev;
	PuglWorld *world;
	char *errMsg;
	VkInstance			instance;
	VkDebugReportCallbackEXT	debugCallback;
	VkSurfaceKHR			surface;
	VkPhysicalDeviceProperties	deviceProperties;
	VkPhysicalDevice		physicalDevice;
	uint32_t			graphicsIndex;
	VkDevice			device;
};

#define RVK_ERRMSG_LEN	4096

void rvkSetErrMsg(struct RenderVulkan *vk, const char *fmt, ...)
{
	vk->errMsg = realloc(vk->errMsg, RVK_ERRMSG_LEN);
	va_list args;
	va_start(args, fmt);
	stbsp_vsnprintf(vk->errMsg, RVK_ERRMSG_LEN, fmt, args);
	va_end(args);
}

void rvkClearErrMsg(struct RenderVulkan *vk)
{
	if (vk->errMsg) {
		free(vk->errMsg);
		vk->errMsg = NULL;
	}
}

const char *rvkGetErrMsg(struct RenderVulkan *vk)
{
	return vk->errMsg;
}

#if defined(_WIN32)
#define VULKAN_SONAME_LATEST	"vulkan-1.dll"
static inline void *appDlopen(const char *soname)
{
	return LoadLibraryA(soname);
}

static inline char *appDlerror()
{
	// TODO: Print a more informative string. Error codes are annoying.
	DWORD errCode = GetLastError();
	static APP_THREAD_LOCAL char errStr[64];
	stbsp_snprintf(errStr, sizeof(errStr), "Dynamic Library Error: %d", errCode);
	return errStr;
}

static inline void *appDlsym(void *handle, const char *symbol)
{
	const uintptr_t ulAddr = (uintptr_t)GetProcAddress(handle, symbol);
	return (void*)ulAddr;
}

static inline int appDlclose(void *handle)
{
	return FreeLibrary(handle);
}

PuglStatus getRequiredInstanceExtensions(PuglWorld *world,
		uint32_t *pExtensionCount,
		const char **const ppExtensionNames)
{
	if (!world) {
		if (pExtensionCount) *pExtensionCount = 0;
		if (ppExtensionNames) *ppExtensionNames = NULL;
		return PUGL_FAILURE;
	}
	static const char *const required[] = {
		VK_KHR_SURFACE_EXTENSION_NAME,
		VK_KHR_WIN32_SURFACE_EXTENSION_NAME
	};
	static const uint32_t num = sizeof(required) / sizeof(required[0]);
	if (ppExtensionNames) {
		for (uint32_t i = 0; i < num; ++i) {
			ppExtensionNames[i] = required[i];
		}
	} else {
		*pExtensionCount = num;
	}
	return PUGL_SUCCESS;
}

VkResult createVulkanSurface(PuglView *view,
		VkInstance instance,
		PFN_vkGetInstanceProcAddr getInstanceProcAddrFunc,
		const VkAllocationCallbacks *pAllocator,
		VkSurfaceKHR *pSurface)
{
	PuglWorld *world = ((struct PuglViewImpl*)view)->world;
	VkWin32SurfaceCreateInfoKHR createInfo = { 0 };
	createInfo.sType = VK_STRUCTURE_TYPE_WIN32_SURFACE_CREATE_INFO_KHR;
	createInfo.hinstance = GetModuleHandle(0);	// FIXME
	createInfo.hwnd = puglGetNativeWindow(view);
	PFN_vkCreateWin32SurfaceKHR vkCreateWin32SurfaceKHR;
	uintptr_t *const ulCreateWin32SurfaceKHR = (uintptr_t*)&vkCreateWin32SurfaceKHR;
	*ulCreateWin32SurfaceKHR = (uintptr_t)getInstanceProcAddrFunc(instance, "vkCreateWin32SurfaceKHR");
	return vkCreateWin32SurfaceKHR(instance, &createInfo, pAllocator, pSurface);
}
#else
#define VULKAN_SONAME_LATEST	"libvulkan.so.1"
#include <dlfcn.h>
// XXX: puglDlopen() and friends
static inline void *appDlopen(const char *soname)
{
	return dlopen(soname, RTLD_NOW);
}

static inline char *appDlerror()
{
	return dlerror();
}

static inline void *appDlsym(void *handle, const char *symbol)
{
	return dlsym(handle, symbol);
}

static inline int appDlclose(void *handle)
{
	return dlclose(handle);
}

/* XXX:  puglGetRequiredInstanceExtensions()
 *       "Get the platform-specific names of the required instance-level 
 *        extensions if you want to display your images to the screen."
 *       Reminder that Vulkan is off-screen by default.
 *
 * TODO: Linux actually has three possible surfaces: Xlib, XCB, and Wayland.
 *       This should be figured out at runtime (without using #ifdefs).
 *       In which case, `world` will be used to determine which to use.
 *       As of now, Pugl (and LV2! suil, etc.) only supports Xlib, but the
 *       variable should be left in the function signature for forward
 *       compatibility.
 */
PuglStatus getRequiredInstanceExtensions(PuglWorld *world,
		uint32_t *pExtensionCount,
		const char **const ppExtensionNames)
{
	if (!world) {
		if (pExtensionCount) *pExtensionCount = 0;
		if (ppExtensionNames) *ppExtensionNames = NULL;
		return PUGL_FAILURE;
	}
	// TODO: if (world->system == X11) { ... } else if (world->system == Wayland) { ... } else ...
	static const char *const required[] = {
		VK_KHR_SURFACE_EXTENSION_NAME,
		VK_KHR_XLIB_SURFACE_EXTENSION_NAME
	};
	static const uint32_t num = sizeof(required) / sizeof(required[0]);
	if (ppExtensionNames) {
		for (uint32_t i = 0; i < num; ++i) {
			ppExtensionNames[i] = required[i];
		}
	} else {
		*pExtensionCount = num;
	}
	return PUGL_SUCCESS;
}

/* XXX: puglCreateVulkanSurface()
 *
 *      Creating a surface is platform-specific and should be handled by Pugl
 *      with this function exposed publicly.
 *
 *      No need to wrap vkFreeSurfaceKHR(). Creating a surface is platform
 *      specific, but freeing it is not.
 */
VkResult createVulkanSurface(PuglView *view,
		VkInstance instance,
		PFN_vkGetInstanceProcAddr getInstanceProcAddrFunc,
		const VkAllocationCallbacks *pAllocator,
		VkSurfaceKHR *pSurface)
{
	PuglWorld *world = ((struct PuglViewImpl*)view)->world;
	VkXlibSurfaceCreateInfoKHR createInfo = { 0 };
	createInfo.sType = VK_STRUCTURE_TYPE_XLIB_SURFACE_CREATE_INFO_KHR;
	createInfo.dpy = ((struct PuglWorldImpl*)world)->impl->display;
	createInfo.window = puglGetNativeWindow(view);
	PFN_vkCreateXlibSurfaceKHR vkCreateXlibSurfaceKHR;
	uintptr_t *const ulCreateXlibSurfaceKHR = (uintptr_t*)&vkCreateXlibSurfaceKHR;
	*ulCreateXlibSurfaceKHR = (uintptr_t)getInstanceProcAddrFunc(instance, "vkCreateXlibSurfaceKHR");
	return vkCreateXlibSurfaceKHR(instance, &createInfo, pAllocator, pSurface);
}
#endif

void *loadVulkanLibrary(const char *prefix)
{
	(void)prefix;	// TODO
	void *handle = appDlopen(VULKAN_SONAME_LATEST);
	return handle;
}

void loadVulkanGetInstanceProcAddrFunc(void *handle,
		PFN_vkGetInstanceProcAddr *getInstanceProcAddrFunc)
{
	uintptr_t *ulGetInstanceProcAddrFunc = (uintptr_t*)getInstanceProcAddrFunc;
	*ulGetInstanceProcAddrFunc = (uintptr_t)appDlsym(handle, "vkGetInstanceProcAddr");
}

int unloadVulkanLibrary(void *handle)
{
	if (handle) {
		return appDlclose(handle);
	}
	return 0;
}

static VKAPI_ATTR VkBool32 VKAPI_CALL debugCallback(
		VkDebugReportFlagsEXT flags,
		VkDebugReportObjectTypeEXT objType,
		uint64_t obj,
		size_t location,
		int32_t code,
		const char *layerPrefix,
		const char *msg,
		void *userData
		)
{
	fprintf(stderr, "\nValidation layer:\n%s\n\n", msg);
	return VK_FALSE;
}

static VkResult rvkCreateInstance(struct RenderVulkan *vk,
	const uint32_t nLayers, const char *const *const layers,
	const uint32_t nAdditional, const char *const *const additionalExtensions)
{
	VkApplicationInfo appInfo = { 0 };
	appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
	appInfo.pApplicationName = "Pugl Vulkan Test";
	appInfo.applicationVersion = VK_MAKE_VERSION(0, 1, 0);
	appInfo.pEngineName = "Pugl Vulkan Test Engine";
	appInfo.engineVersion = VK_MAKE_VERSION(0, 1, 0);
	/* MoltenVK for macOS currently only supports Vulkan 1.0 */
	appInfo.apiVersion = VK_MAKE_VERSION(1, 0, 0);

	uint32_t i, j, nRequired;
	getRequiredInstanceExtensions(vk->world, &nRequired, NULL);

	const uint32_t nExtensions = nRequired + nAdditional;
	const char **const extensions = malloc(sizeof(const char*) * nExtensions);

	getRequiredInstanceExtensions(vk->world, NULL, extensions);
	for (i = nRequired, j = 0; i < nExtensions; ++i, ++j) {
		extensions[i] = additionalExtensions[j];
	}

	for (i = 0; i < nExtensions; ++i) {
		printf("Using instance extension:\t%s\n", extensions[i]);
	}

	for (i = 0; i < nLayers; ++i) {
		printf("Using instance layer:\t\t%s\n", layers[i]);
	}

	VkInstanceCreateInfo createInfo = { 0 };
	createInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
	createInfo.pApplicationInfo = &appInfo;
	createInfo.enabledLayerCount = nLayers;
	createInfo.ppEnabledLayerNames = layers;
	createInfo.enabledExtensionCount = nExtensions;
	createInfo.ppEnabledExtensionNames = extensions;

	VkResult result = VK_SUCCESS;
	if ((result = vk->api->vkCreateInstance(&createInfo, ALLOC_VK, &vk->instance))) {
		rvkSetErrMsg(vk, "Could not create Vulkan Instance: %d\n", result);
	}
	free(extensions);
	return result;
}

/** Must not be called until all derivative objects are destroyed first */
static void rvkDestroyInstance(struct RenderVulkan *vk)
{
	vk->api->vkDestroyInstance(vk->instance, ALLOC_VK);
	vk->instance = VK_NULL_HANDLE;
}

void rvkDestroy(struct RenderVulkan *vk);

/** Create a self-contained Vulkan instance and set up a debug reporter
 *
 * XXX
 *
 * At the moment `world` is not used for anything, but if/when Pugl supports
 * dynamically choosing a backend (X11, XCB, Wayland), it is anticipated that
 * `world` will contain information regarding which is in use, which will then
 * be used by `createVulkanSurface`.
 *
 * If creating a surface is handled by Pugl (`puglCreateVulkanSurface`), then
 * `PuglWorld` can remain completely opaque to the application.
 *
 * `world` is NOT internally managed by the application. It MUST be destroyed
 * separately.
 *
 * If errors occurred, the struct will be returned in an unusable state,
 * and MUST be checked via `rvkGetErrMsg`. It MUST then be destroyed via
 * `rvkDestroy`.
 * */
int rvkCreate(PuglWorld *world, struct RenderVulkan **vkOut)
{
	static const char *const instanceLayers[] = {
		"VK_LAYER_KHRONOS_validation"
	};
	const uint32_t nInstanceLayers = sizeof(instanceLayers) / sizeof(instanceLayers[0]);
	static const char *const instanceExtensions[] = {
		VK_EXT_DEBUG_REPORT_EXTENSION_NAME
	};
	const uint32_t nInstanceExtensions = sizeof(instanceExtensions) / sizeof(instanceExtensions[0]);

	struct RenderVulkan *vk = calloc(1, sizeof(*vk));
	if (!world) {
		rvkSetErrMsg(vk, "No PuglWorld provided");
		return -1;
	}
	vk->world = world;
	vk->api = calloc(1, sizeof(*vk->api));

	vk->api->handle = loadVulkanLibrary(NULL);
	if (!vk->api->handle) {
		rvkSetErrMsg(vk, "Error loading Vulkan shared library:\n%s\n", appDlerror());
		return -1;
	}

	loadVulkanGetInstanceProcAddrFunc(vk->api->handle, &vk->api->vkGetInstanceProcAddr);
	if (!vk->api->vkGetInstanceProcAddr) {
		rvkSetErrMsg(vk, "Error loading `vkGetInstanceProcAddr`:\n%s", appDlerror());
		return -1;
	}

	uintptr_t *const ulCreateInstance = (uintptr_t*)&vk->api->vkCreateInstance;
	*ulCreateInstance = (uintptr_t)vk->api->vkGetInstanceProcAddr(NULL, "vkCreateInstance");
	if (!vk->api->vkCreateInstance) {
		rvkSetErrMsg(vk, "Error loading `vkCreateInstance`");
		return -1;
	}

	VkResult result;
	//if ((result = rvkCreateInstance(vk, 0, NULL, 0, NULL))) {
	if ((result = rvkCreateInstance(vk, nInstanceLayers, instanceLayers, nInstanceExtensions, instanceExtensions))) {
		return -1;
	}

	static const char *const strErrLd = "Error loading instance function %s";

	static const char *const strDestroyInstance = "vkDestroyInstance";
	uintptr_t *const ulDestroyInstance = (uintptr_t*)&vk->api->vkDestroyInstance;
	*ulDestroyInstance = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strDestroyInstance);
	if (!vk->api->vkDestroyInstance) {
		rvkSetErrMsg(vk, strErrLd, strDestroyInstance);
		return -1;
	}

	/* It is okay if debug reporter functions are not resolved (for now) */
	uintptr_t *ulCreateDebugReportCallbackEXT = (uintptr_t*)&vk->api->vkCreateDebugReportCallbackEXT;
	*ulCreateDebugReportCallbackEXT = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, "vkCreateDebugReportCallbackEXT");

	uintptr_t *ulDestroyDebugReportCallbackEXT = (uintptr_t*)&vk->api->vkDestroyDebugReportCallbackEXT;
	*ulDestroyDebugReportCallbackEXT = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, "vkDestroyDebugReportCallbackEXT");

	/* But not if we are unable to destroy a created debug reporter */
	if (vk->api->vkCreateDebugReportCallbackEXT && !vk->api->vkDestroyDebugReportCallbackEXT) {
		rvkSetErrMsg(vk, "No debug reporter destroy function loaded for corresponding create function\n");
		return -1;
	}

	/* Dynamically load instance-level Vulkan function pointers via `vkGetInstanceProcAddr`
	 *
	 * TODO: This could perhaps be generated by a script and put into a separate "loader" file
	 *
	 * Casts to `uintptr_t` as an intermediary to suppress warnings when compiling with `-Wpedantic`
	 */
	static const char *const strDestroySurfaceKHR = "vkDestroySurfaceKHR";
	uintptr_t *ulDestroySurfaceKHR = (uintptr_t*)&vk->api->vkDestroySurfaceKHR;
	*ulDestroySurfaceKHR = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strDestroySurfaceKHR);
	if (!vk->api->vkDestroySurfaceKHR) {
		rvkSetErrMsg(vk, strErrLd, strDestroySurfaceKHR);
		return -1;
	}

	static const char *const strEnumeratePhysicalDevices = "vkEnumeratePhysicalDevices";
	uintptr_t *ulEnumeratePhysicalDevices = (uintptr_t*)&vk->api->vkEnumeratePhysicalDevices;
	*ulEnumeratePhysicalDevices = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strEnumeratePhysicalDevices);
	if (!vk->api->vkEnumeratePhysicalDevices) {
		rvkSetErrMsg(vk, strErrLd, strEnumeratePhysicalDevices);
		return -1;
	}

	static const char *const strGetPhysicalDeviceProperties = "vkGetPhysicalDeviceProperties";
	uintptr_t *ulGetPhysicalDeviceProperties = (uintptr_t*)&vk->api->vkGetPhysicalDeviceProperties;
	*ulGetPhysicalDeviceProperties = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strGetPhysicalDeviceProperties);
	if (!vk->api->vkGetPhysicalDeviceProperties) {
		rvkSetErrMsg(vk, strErrLd, strGetPhysicalDeviceProperties);
		return -1;
	}

	static const char *const strGetPhysicalDeviceQueueFamilyProperties = "vkGetPhysicalDeviceQueueFamilyProperties";
	uintptr_t *ulGetPhysicalDeviceQueueFamilyProperties = (uintptr_t*)&vk->api->vkGetPhysicalDeviceQueueFamilyProperties;
	*ulGetPhysicalDeviceQueueFamilyProperties = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strGetPhysicalDeviceQueueFamilyProperties);
	if (!vk->api->vkGetPhysicalDeviceQueueFamilyProperties) {
		rvkSetErrMsg(vk, strErrLd, strGetPhysicalDeviceQueueFamilyProperties);
		return -1;
	}

	static const char *const strGetPhysicalDeviceSurfaceSupportKHR = "vkGetPhysicalDeviceSurfaceSupportKHR";
	uintptr_t *ulGetPhysicalDeviceSurfaceSupportKHR = (uintptr_t*)&vk->api->vkGetPhysicalDeviceSurfaceSupportKHR;
	*ulGetPhysicalDeviceSurfaceSupportKHR = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strGetPhysicalDeviceSurfaceSupportKHR);
	if (!vk->api->vkGetPhysicalDeviceSurfaceSupportKHR) {
		rvkSetErrMsg(vk, strErrLd, strGetPhysicalDeviceSurfaceSupportKHR);
		return -1;
	}

	static const char *const strGetPhysicalDeviceMemoryProperties = "vkGetPhysicalDeviceMemoryProperties";
	uintptr_t *ulGetPhysicalDeviceMemoryProperties = (uintptr_t*)&vk->api->vkGetPhysicalDeviceMemoryProperties;
	*ulGetPhysicalDeviceMemoryProperties = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strGetPhysicalDeviceMemoryProperties);
	if (!vk->api->vkGetPhysicalDeviceMemoryProperties) {
		rvkSetErrMsg(vk, strErrLd, strGetPhysicalDeviceMemoryProperties);
		return -1;
	}

	static const char *const strEnumerateDeviceExtensionProperties = "vkEnumerateDeviceExtensionProperties";
	uintptr_t *ulEnumerateDeviceExtensionProperties = (uintptr_t*)&vk->api->vkEnumerateDeviceExtensionProperties;
	*ulEnumerateDeviceExtensionProperties = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strEnumerateDeviceExtensionProperties);
	if (!vk->api->vkEnumerateDeviceExtensionProperties) {
		rvkSetErrMsg(vk, strErrLd, strEnumerateDeviceExtensionProperties);
		return -1;
	}

	static const char *const _vkCreateDevice = "vkCreateDevice";
	uintptr_t *__vkCreateDevice = (uintptr_t*)&vk->api->vkCreateDevice;
	*__vkCreateDevice = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, _vkCreateDevice);
	if (!vk->api->vkCreateDevice) {
		rvkSetErrMsg(vk, strErrLd, _vkCreateDevice);
		return -1;
	}

	static const char *const strGetDeviceProcAddr = "vkGetDeviceProcAddr";
	uintptr_t *ulGetDeviceProcAddr = (uintptr_t*)&vk->api->vkGetDeviceProcAddr;
	*ulGetDeviceProcAddr = (uintptr_t)vk->api->vkGetInstanceProcAddr(vk->instance, strGetDeviceProcAddr);
	if (!vk->api->vkGetDeviceProcAddr) {
		rvkSetErrMsg(vk, strErrLd, strGetDeviceProcAddr);
		return -1;
	}

	/* End loading function pointers */

	if (vk->api->vkCreateDebugReportCallbackEXT) {
		printf("Creating debug reporter\n");
		VkDebugReportCallbackCreateInfoEXT debugInfo = { 0 };
		debugInfo.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT;
		debugInfo.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT;
		debugInfo.pfnCallback = debugCallback;
		if ((result = vk->api->vkCreateDebugReportCallbackEXT(vk->instance,
						&debugInfo, ALLOC_VK, &vk->debugCallback))) {
			rvkSetErrMsg(vk, "Could not create debug reporter: %d", result);
			return -1;
		}
	}

	*vkOut = vk;
	return 0;
}

static int rvkCreateSurface(struct RenderVulkan *vk, PuglView *view)
{
	VkResult result;
	if ((result = createVulkanSurface(view, vk->instance, vk->api->vkGetInstanceProcAddr, ALLOC_VK, &vk->surface))) {
		rvkSetErrMsg(vk, "Could not create window surface: %d\n", result);
		return -1;
	}
	return 0;
}

/** Checks if a particular physical device is suitable for this application.
 *
 * This function is referentially transparent.
 *
 * Choosing a physical device is an *extremely* application-specific procedure.
 *
 * All rendering in Vulkan is done off-screen by default. To get rendered
 * results on-screen they must be "presented" to a surface.
 * The Vulkan spec allows devices to have presentation done on a separate queue
 * family than GRAPHICS, or no present support at all. However, every graphics
 * card today that is capable of connecting to a display has at least one queue
 * family capable of both GRAPHICS and present.
 *
 * This single-threaded application will use only one queue for all operations.
 * More specifically, it will make use of GRAPHICS and TRANSFER operations on
 * a single queue retrieved from a GRAPHICS queue family that supports present.
 *
 * In my experience, most cards follow this format:
 *
 * INTEGRATED: Typically have one queue family for all operations.
 *             May retrieve only one queue from this single queue family.
 * DEDICATED:  Older cards typically have one queue family for GRAPHICS and one
 *             for TRANSFER. Newer cards typically have a separate queue family
 *             for COMPUTE. Remember that all GRAPHICS queue families
 *             implicitly allow both COMPUTE and TRANSFER operations on it as
 *             well. Programmers making use of separate queue families may allow
 *             devices to work more efficiently.
 *
 *             May typically retrieve up to a few queues from either queue
 *             family. The maximum number of available queues is specific to
 *             that device's queue families. Programmers making use of separate
 *             queues for highly independent workloads may allow devices to work
 *             more efficiently. Queues must be used from a single thread, so
 *             programmers wanting to make use of multithreaded queue submission
 *             must retrieve queues per-thread.
 *
 *             GOTCHA: Some devices may have multiple GRAPHICS queue families
 *                     with only one of them able to present. Do not assume a
 *                     device is unsuitable until ALL queue families have been
 *                     checked.
 *
 * Because this application will load all resources before any rendering begins,
 * and the amount of resources are small enough to be loaded almost instantly,
 * it will not make use of a separate TRANSFER queue family.
 *
 * Information for many devices is available online at
 * https://vulkan.gpuinfo.org/
 */
static bool rvkIsDeviceSuitable(const struct RenderVulkan *const vk,
		const VkPhysicalDevice physicalDevice,
		uint32_t *const graphicsIndex)
{
	uint32_t nQueueFamilies;
	vk->api->vkGetPhysicalDeviceQueueFamilyProperties(physicalDevice, &nQueueFamilies, NULL);
	VkQueueFamilyProperties *queueProperties = malloc(nQueueFamilies * sizeof(*queueProperties));
	vk->api->vkGetPhysicalDeviceQueueFamilyProperties(physicalDevice, &nQueueFamilies, queueProperties);
	for (uint32_t i = 0; i < nQueueFamilies; ++i) {
		printf("Queue Family %d queueCount:\t%d\n", i, queueProperties[i].queueCount);
	}
	uint32_t g;
	for (g = 0; g < nQueueFamilies; ++g) {
		if (queueProperties[g].queueFlags & VK_QUEUE_GRAPHICS_BIT) {
			VkBool32 canSurface;
			vk->api->vkGetPhysicalDeviceSurfaceSupportKHR(physicalDevice, g, vk->surface, &canSurface);
			if (canSurface) break;
		}
	}
	free(queueProperties);
	if (g >= nQueueFamilies) {
		/* We only support graphics and present on the same queue family. */
		printf("No graphics+support queue families found on this device\n");
		return false;
	}
	VkBool32 canSwapchain = VK_FALSE;
	uint32_t nExtensions;
	vk->api->vkEnumerateDeviceExtensionProperties(physicalDevice, NULL, &nExtensions, NULL);
	VkExtensionProperties *availableExtensions = malloc(nExtensions * sizeof(*availableExtensions));
	vk->api->vkEnumerateDeviceExtensionProperties(physicalDevice, NULL, &nExtensions, availableExtensions);
	for (uint32_t i = 0; i < nExtensions; ++i) {
		if (!strcmp(availableExtensions[i].extensionName, VK_KHR_SWAPCHAIN_EXTENSION_NAME)) {
			canSwapchain = VK_TRUE;
			break;
		}
	}
	free(availableExtensions);
	if (!canSwapchain) {
		printf("Cannot use a swapchain on this device\n");
		return false;
	}
	*graphicsIndex = g;
	return true;
}

/** Selects a physical device
 *
 * This application will not attempt to find the "most powerful" device on the
 * system, and will choose the first suitable device it finds.
 */
int rvkSelectPhysicalDevice(struct RenderVulkan *vk)
{
	int ret = 0;
	if (!vk->surface) {
		rvkSetErrMsg(vk, "Cannot select a physical device without a surface");
		return -1;
	}
	static const char *const strErrEnum = "Could not enumerate physical devices: %s";
	static const char *const strWarnEnum = "Warn: Incomplete enumeration of physical devices";
	uint32_t nDevices;
	VkResult result;
	if ((result = vk->api->vkEnumeratePhysicalDevices(vk->instance, &nDevices, NULL))) {
		if (result != VK_INCOMPLETE) {
			rvkSetErrMsg(vk, strErrEnum, result);
			return -1;
		} else {
			fprintf(stderr, "%s\n", strWarnEnum);
		}
	}
	if (!nDevices) {
		rvkSetErrMsg(vk, "No physical devices found");
		return -1;
	}
	VkPhysicalDevice *devices = malloc(nDevices * sizeof(*devices));
	VkPhysicalDeviceProperties *deviceProperties = malloc(nDevices * sizeof(*deviceProperties));
	if ((result = vk->api->vkEnumeratePhysicalDevices(vk->instance, &nDevices, devices))) {
		if (result != VK_INCOMPLETE) {
			rvkSetErrMsg(vk, strErrEnum, result);
			ret = -1;
			goto done;
		} else {
			fprintf(stderr, "%s\n", strWarnEnum);
		}
	}

	uint32_t i;
	for (i = 0; i < nDevices; ++i) {
		vk->api->vkGetPhysicalDeviceProperties(devices[i], &deviceProperties[i]);
		printf("Found physical device:\t\t`%s`\n", deviceProperties[i].deviceName);
	}
	for (i = 0; i < nDevices; ++i) {
		printf("Checking suitability for\t`%s`...\n", deviceProperties[i].deviceName);
		uint32_t graphicsIndex;
		if (rvkIsDeviceSuitable(vk, devices[i], &graphicsIndex)) {
			printf("Using physical device:\t\t`%s`\n", deviceProperties[i].deviceName);
			vk->deviceProperties = deviceProperties[i];
			vk->physicalDevice = devices[i];
			vk->graphicsIndex = graphicsIndex;
			printf("Graphics Index:\t\t\t%d\n", vk->graphicsIndex);
			goto done;
		}
		printf("Device `%s` not suitable\n", deviceProperties[i].deviceName);
	}
	if (i >= nDevices) {
		rvkSetErrMsg(vk, "No suitable devices found");
		ret = -1;
	}
done:
	free(deviceProperties);
	free(devices);
	return ret;
}

static int rvkLoadDeviceFunctions(struct RenderVulkan *vk, VkDevice device)
{
	const char *const strErrLd = "Error loading device function %s";

	static const char *const _vkDestroyDevice = "vkDestroyDevice";
	uintptr_t *__vkDestroyDevice = (uintptr_t*)&vk->dev->vkDestroyDevice;
	*__vkDestroyDevice = (uintptr_t)vk->api->vkGetDeviceProcAddr(device, _vkDestroyDevice);
	if (!vk->dev->vkDestroyDevice) {
		rvkSetErrMsg(vk, strErrLd, _vkDestroyDevice);
		return -1;
	}

	static const char *const _vkDeviceWaitIdle = "vkDeviceWaitIdle";
	uintptr_t *__vkDeviceWaitIdle = (uintptr_t*)&vk->dev->vkDeviceWaitIdle;
	*__vkDeviceWaitIdle = (uintptr_t)vk->api->vkGetDeviceProcAddr(device, _vkDeviceWaitIdle);
	if (!vk->dev->vkDeviceWaitIdle) {
		rvkSetErrMsg(vk, strErrLd, _vkDeviceWaitIdle);
		return -1;
	}

	return 0;
}

int rvkOpenDevice(struct RenderVulkan *vk)
{
	if (vk->device) {
		rvkSetErrMsg(vk, "Renderer already has an opened device");
		return -1;
	}
	const float graphicsQueuePriority = 1.0f;
	const char *const swapchainName = VK_KHR_SWAPCHAIN_EXTENSION_NAME;
	VkDeviceQueueCreateInfo queueCreateInfo = { 0 };
	queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
	queueCreateInfo.queueFamilyIndex = vk->graphicsIndex;
	queueCreateInfo.queueCount = 1;
	queueCreateInfo.pQueuePriorities = &graphicsQueuePriority;

	VkDeviceCreateInfo createInfo = { 0 };
	createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
	createInfo.queueCreateInfoCount = 1;
	createInfo.pQueueCreateInfos = &queueCreateInfo;
	/* `enabledLayerCount` and `ppEnabledLayerNames` are ignored by modern Vulkan implementations.
	 * TODO: But maybe it is a good idea to support the older implementations.
	 */
	createInfo.enabledExtensionCount = 1;
	createInfo.ppEnabledExtensionNames = &swapchainName;
	/* This application uses no device features. */
	createInfo.pEnabledFeatures = NULL;

	VkDevice device;
	VkResult result;
	if ((result = vk->api->vkCreateDevice(vk->physicalDevice, &createInfo, ALLOC_VK, &device))) {
		rvkSetErrMsg(vk, "Could not open device `%s`: %d\n",
				vk->deviceProperties.deviceName, result);
		return -1;
	}
	vk->dev = calloc(1, sizeof(*vk->dev));
	vk->device = device;
	if (rvkLoadDeviceFunctions(vk, device)) {
		return -1;
	}
	return 0;
}

static void rvkCloseDevice(struct RenderVulkan *vk)
{
	if (vk->dev->vkDestroyDevice) {
		vk->dev->vkDestroyDevice(vk->device, ALLOC_VK);
	} else {
		fprintf(stderr, "Fatal: Unable to destroy logical device (missing function pointer)\n");
	}
	free(vk->dev);
	vk->dev = NULL;
	vk->device = VK_NULL_HANDLE;
}

/** This must work no matter the current state of `vk` */
void rvkDestroy(struct RenderVulkan *vk)
{
	if (vk) {
		/* `vk->device` implies `vk->dev` but device functions MAY not be loaded */
		if (vk->device) {
			if (vk->dev->vkDeviceWaitIdle) vk->dev->vkDeviceWaitIdle(vk->device);
			rvkCloseDevice(vk);
		}
		if (vk->surface) vk->api->vkDestroySurfaceKHR(vk->instance, vk->surface, ALLOC_VK);
		if (vk->debugCallback) {
			/* `vk->debugCallback` implies `vk->api` and all instance functions loaded */
			vk->api->vkDestroyDebugReportCallbackEXT(vk->instance, vk->debugCallback, ALLOC_VK);
		}
		if (vk->instance) rvkDestroyInstance(vk);
		if (vk->api) {
			if (vk->api->handle) unloadVulkanLibrary(vk->api->handle);
			free(vk->api);
		}
		if (vk->errMsg) free(vk->errMsg);
		free(vk);
	}
}

/* Normally, we would NOT exit the entire process on errors when running as
 * part of a larger process, but since we own this process, there isn't anything
 * else to do. As a plugin, we would destroy the window and all memory
 * associated with it, leaving the larger process intact.
 */
static void rvkFatal(struct RenderVulkan *vk)
{
	fprintf(stderr, "%s\n", rvkGetErrMsg(vk));
	rvkDestroy(vk);
	if (vk->world) {
		puglFreeWorld(vk->world);
	}
	printf("Aborting gracefully\n");
	exit(1);
}

#define CHECK_RVK(rvk, expr)	do { if ((expr)) { rvkFatal(rvk); }  } while (0)

int running = 1;

PuglStatus onEvent(PuglView *view, const PuglEvent *e)
{
	printEvent(e, "Event:\t", true);
	switch (e->type) {
		case PUGL_CLOSE:
			running = 0;
			break;
		default:
			break;
	}
	return PUGL_SUCCESS;
}

int main()
{
#if defined(__linux__)
	/* The Mesa Vulkan drivers require this to be called */
	XInitThreads();
#endif
	PuglWorld *world = puglNewWorld();

	/* Vulkan application that uses Pugl for windows and events */
	struct RenderVulkan *vk = NULL;
	CHECK_RVK(vk, rvkCreate(world, &vk));

	printf("Created Vulkan Instance Successfully\n");

	PuglView *view = puglNewView(world);
	const PuglRect frame = { 0, 0, 800, 600 };
	puglSetBackend(view, puglStubBackend());

	PuglStatus status;
	if ((status = puglCreateWindow(view, "Vulkan Application Using Pugl"))) {
		fprintf(stderr, "Could not create window: %d\n", status);
		rvkFatal(vk);
	}
	puglSetEventFunc(view, onEvent);

	CHECK_RVK(vk, rvkCreateSurface(vk, view));
	CHECK_RVK(vk, rvkSelectPhysicalDevice(vk));
	CHECK_RVK(vk, rvkOpenDevice(vk));

	printf("Opened Vulkan Device Successfully\n");

	puglShowWindow(view);
	while (running) {
		puglPollEvents(world, -1);
		puglDispatchEvents(world);
	}

	puglFreeView(view);
	puglFreeWorld(world);
	/* Vulkan library MUST be unloaded AFTER call to XCloseDisplay() or it will segfault (?) */
	rvkDestroy(vk);
	printf("Exiting gracefully\n");
	return 0;
}

#if 0
#if defined(_WIN32)
int WINAPI WinMain(
		HINSTANCE hInstance,
		HINSTANCE hPrevInstance,
		LPSTR lpCmdLine,
		int nCmdShow
		)
{
	(void)hInstance;
	(void)hPrevInstance;
	(void)lpCmdLine;
	(void)nCmdShow;
	return main();
}
#endif /* _WIN32 */
#endif /* 0 */