#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>

#include <vulkan/vulkan.h>

// check for half precision floating point support, for x86 this is equivalent to
// checking for SSE2
#define SUPPORTS_NATIVE_FP16 (__x86_64__ == 1 && __SSE2__ == 1)
// print debug messages
#define DEBUG		     1
#define VERBOSE		     0

// define half precision floating point
#if SUPPORTS_NATIVE_FP16
// extension is needed due to -pedantic
__extension__ typedef _Float16 half;
#endif

const char    *vk_validation_layer[]  = {"VK_LAYER_KHRONOS_validation"};
const uint32_t vk_validation_layer_no = 1;

// FIXME: including vulkan/vk_enum_string_helper.h does not compile
extern const char *vk_Result_to_str(VkResult input);

// like printf but on stderr
int err(const char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);
	int ret = vfprintf(stderr, fmt, ap);
	va_end(ap);
	return ret;
}

// print out all the instance extensions
// NOTE: these are different from device and shader extensions
int vk_enumerate_instance_extensions(void)
{
	uint32_t ex_no = 0;
#if VERBOSE > 0
	vkEnumerateInstanceExtensionProperties(NULL, &ex_no, NULL);
	VkExtensionProperties *ex_arr =
	    malloc(sizeof(VkExtensionProperties) * ex_no);
	if (ex_arr == NULL) {
		err("ERROR: in %s: %s\n", __func__, strerror(errno));
		return -1;
	}
	vkEnumerateInstanceExtensionProperties(NULL, &ex_no, ex_arr);
	printf("Available Properties: \n");
	for (uint32_t i = 0; i < ex_no; i++) {
		printf("\t%s\n", ex_arr[i].extensionName);
	}
	free(ex_arr);
#endif
	return ex_no;
}

// on debug check for support of validation layers and activate one, a validation
// layer is useful to do more error checking at runtime like ckecking for invalid
// arguments, validation layers are available only if vulkan-sdk is installed
// (vulkan-devel on arch)
int vk_activate_validation_layer(VkInstanceCreateInfo *cinfo)
{
	uint32_t prop_no = 0;
#if DEBUG > 0
	vkEnumerateInstanceLayerProperties(&prop_no, NULL);

	VkLayerProperties *prop_arr = malloc(sizeof(VkLayerProperties) * prop_no);
	if (prop_arr == NULL) {
		err("ERROR: in %s: %s\n", __func__, strerror(errno));
		return -1;
	}
	vkEnumerateInstanceLayerProperties(&prop_no, prop_arr);

	for (uint32_t i = 0; i < prop_no; i++) {
		if (strcmp(prop_arr[i].layerName, vk_validation_layer[0]) == 0) {
			cinfo->enabledLayerCount   = vk_validation_layer_no;
			cinfo->ppEnabledLayerNames = vk_validation_layer;
			free(prop_arr);
			return 0;
		}
	}
	free(prop_arr);
	return 1;
#endif
	return 0;
}

VkInstance vk_init(void)
{
	// create a vulkan instance and fill it with the application data
	VkResult   res;
	VkInstance vk_instance = VK_NULL_HANDLE;

	VkApplicationInfo vk_appinfo = {
	    .sType		= VK_STRUCTURE_TYPE_APPLICATION_INFO,
	    .pNext		= NULL,
	    .pApplicationName	= __FILE__,
	    .applicationVersion = VK_MAKE_VERSION(0, 1, 0),
	    .pEngineName	= "no engine",
	    .engineVersion	= VK_MAKE_VERSION(0, 0, 0),
	    .apiVersion		= VK_API_VERSION_1_3,
	};

	vk_enumerate_instance_extensions();

	// TODO: check for extension availability
	// TODO: does the lifetime of VkInstanceCreateInfo has to be the same as the
	//       lifetime of VkInstance?
	const char *vk_instance_extensions[] = {
	    VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME,
	};
	const uint32_t vk_instance_extensions_no =
	    (uint32_t)(sizeof(vk_instance_extensions) / sizeof(char *));

	VkInstanceCreateInfo vk_instanceinfo = {
	    .sType	      = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO,
	    .pApplicationInfo = &vk_appinfo,
	    .flags	      = VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR,
	    .enabledExtensionCount   = vk_instance_extensions_no,
	    .ppEnabledExtensionNames = vk_instance_extensions,
	    .enabledLayerCount	     = 0,
	};

	int e = 0;
	if ((e = vk_activate_validation_layer(&vk_instanceinfo))) {
		err("Could not activate validation layers%s\n",
		    e > 0 ? ": No validation layers found" : "");
	}

	res = vkCreateInstance(&vk_instanceinfo, NULL, &vk_instance);
	if (res != VK_SUCCESS) {
		err("ERROR: Could not create vulkan instance %s",
		    vk_Result_to_str(res));
		return VK_NULL_HANDLE;
	} else {
#if VERBOSE > 0
		printf("Created vulkan instance\n");
#endif
	}
	return vk_instance;
}

void vk_destroy(VkInstance vk_instance)
{
	// ...
	vkDestroyInstance(vk_instance, NULL);
}

VkPhysicalDevice vk_physical_device_get(VkInstance vk_instance)
{
	VkPhysicalDevice vk_phydev = VK_NULL_HANDLE;

	uint32_t	  vk_phydevs_no = 0;
	VkPhysicalDevice *vk_phydevs;
	vkEnumeratePhysicalDevices(vk_instance, &vk_phydevs_no, NULL);

	if (vk_phydevs_no == 0) {
		return vk_phydev;
	}

	vk_phydevs = malloc(sizeof(VkPhysicalDevice) * vk_phydevs_no);
	if (vk_phydevs == NULL) {
		err("ERROR: in %s: %s\n", __func__, strerror(errno));
		return NULL;
	}

	vkEnumeratePhysicalDevices(vk_instance, &vk_phydevs_no, vk_phydevs);

	printf("Available Physical Devices: \n");
	for (uint32_t i = 0; i < vk_phydevs_no; i++) {
		VkPhysicalDevice	   device = vk_phydevs[i];
		VkPhysicalDeviceProperties device_properties;
		VkPhysicalDeviceFeatures   device_features;

		vkGetPhysicalDeviceProperties(device, &device_properties);
		vkGetPhysicalDeviceFeatures(device, &device_features);

		printf(
		    "\tDevice %d: %s, Discrete: %s\n",
		    i,
		    device_properties.deviceName,
		    device_properties.deviceType ==
			    VK_PHYSICAL_DEVICE_TYPE_DISCRETE_GPU
			? "true"
			: "false"
		);
	}

	// TODO: find the most suitable physical device, but for now every vulkan
	//       device has to be compatible with compute shaders
	vk_phydev = vk_phydevs[0];

	free(vk_phydevs);
	return vk_phydev;
}

void vk_physical_device_destroy(VkPhysicalDevice vk_phydev)
{
	if (vk_phydev != VK_NULL_HANDLE) {
		// ...
	}
}

// return the index of the first queue family that supports compute on the device,
// returns a negative index on error
int vk_device_compute_queue_index(VkPhysicalDevice vk_phydev)
{
	uint32_t		 vk_qfamilies_no = 0;
	VkQueueFamilyProperties *vk_qfamilies;
	int			 supports = -1;

	vkGetPhysicalDeviceQueueFamilyProperties(vk_phydev, &vk_qfamilies_no, NULL);

	vk_qfamilies = malloc(sizeof(VkQueueFamilyProperties) * vk_qfamilies_no);
	if (vk_qfamilies == NULL) {
		err("ERROR: in %s: %s\n", __func__, strerror(errno));
		return -1;
	}

	vkGetPhysicalDeviceQueueFamilyProperties(
	    vk_phydev, &vk_qfamilies_no, vk_qfamilies
	);

	for (uint32_t i = 0; i < vk_qfamilies_no; i++) {
		if (vk_qfamilies[i].queueFlags & VK_QUEUE_COMPUTE_BIT) {
			supports = i;
		}
	}

	free(vk_qfamilies);
	return supports;
}

VkDevice vk_logical_device_create(VkPhysicalDevice vk_phydev, int qfamily_idx)
{
	VkResult res;
	VkDevice vk_logdev	   = VK_NULL_HANDLE;
	float	 vk_queue_priority = 1.0f;

	// specify which command queues to use for the physical device
	VkDeviceQueueCreateInfo vk_queueinfo = {
	    .sType	      = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO,
	    .pNext	      = NULL,
	    .flags	      = 0,
	    .queueFamilyIndex = qfamily_idx,
	    .queueCount	      = 1,
	    .pQueuePriorities = &vk_queue_priority,
	};

	// specify which device features to use
	// TODO: this
	VkPhysicalDeviceFeatures vk_phydev_features = {0};

	// actually create the logical device
	// TODO: figure out what device extensions are
	// FIXME: here validation layers are ignored but it is still better to define
	//        them for compatibility
	VkDeviceCreateInfo vk_createinfo = {
	    .sType		     = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO,
	    .pQueueCreateInfos	     = &vk_queueinfo,
	    .queueCreateInfoCount    = 1,
	    .pEnabledFeatures	     = &vk_phydev_features,
	    .ppEnabledExtensionNames = NULL,
	    .enabledExtensionCount   = 0,
	    .ppEnabledLayerNames     = NULL,
	    .enabledLayerCount	     = 0,
	};

	res = vkCreateDevice(vk_phydev, &vk_createinfo, NULL, &vk_logdev);
	if (res != VK_SUCCESS) {
		err("ERROR: Could not create vulkan logical device %s",
		    vk_Result_to_str(res));
		return VK_NULL_HANDLE;
	} else {
#if VERBOSE > 0
		printf("Created vulkan logical device\n");
#endif
	}

	return vk_logdev;
}

void vk_logical_device_destroy(VkDevice vk_logdev)
{
	vkDestroyDevice(vk_logdev, NULL);
}

VkQueue vk_queue_get(VkDevice vk_logdev, int qfamily_idx)
{
	VkQueue vk_queue = VK_NULL_HANDLE;
	vkGetDeviceQueue(vk_logdev, qfamily_idx, 0, &vk_queue);
	return vk_queue;
}

int main(void)
{
#if VERBOSE > 0
	if (SUPPORTS_NATIVE_FP16) {
		printf("Processor supports half precision floating point\n");
	} else {
		printf("Processor doesn't support half precision floating point\n");
		return EXIT_FAILURE;
	}
#endif

	VkInstance vk_instance = vk_init();
	if (vk_instance == VK_NULL_HANDLE) {
		exit(EXIT_FAILURE);
	}
	VkPhysicalDevice vk_phydev   = vk_physical_device_get(vk_instance);
	int		 qfamily_idx = vk_device_compute_queue_index(vk_phydev);
	if (qfamily_idx < 0) {
		err("The device does not support compute queues\n");
		exit(EXIT_FAILURE);
	}
	VkDevice vk_logdev = vk_logical_device_create(vk_phydev, qfamily_idx);

	vk_logical_device_destroy(vk_logdev);
	vk_physical_device_destroy(vk_phydev);
	vk_destroy(vk_instance);

	return EXIT_SUCCESS;
}