#include <stdint.h>
#include <stdio.h>
#include <openxr/openxr.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <signal.h>
#include <time.h>

sig_atomic_t stop = false;

void handler(int sig)
{
	stop = true;
}

#define HEADLESS_EXT "XR_MND_headless"

static const char* xr_strerror(XrInstance instance, XrResult err)
{
	static char buffer[XR_MAX_RESULT_STRING_SIZE];
	xrResultToString(instance, err, buffer);
	return buffer;
}

void clear()
{
	puts("\033[H\033[J");
}

int main(int argc, char** argv)
{
	XrInstance instance;
	XrApplicationInfo applicationInfo = {
		.applicationName = "OpenXR Example",
		.engineName = "Example Engine",
		.apiVersion = XR_API_VERSION_1_0,
	};

	uint32_t extentionPropCount;
	xrEnumerateInstanceExtensionProperties(NULL, 0, &extentionPropCount, NULL);
	XrExtensionProperties *proparties = calloc(extentionPropCount, sizeof(*proparties));
	for (uint32_t i = 0; i < extentionPropCount; ++i)
		proparties[i].type = XR_TYPE_EXTENSION_PROPERTIES;
	XrResult result = xrEnumerateInstanceExtensionProperties(NULL, extentionPropCount, &extentionPropCount, proparties);
	if (!XR_SUCCEEDED(result)) {
		printf("Failed to query OpenXR extensions: %d\n", result);
		return 1;
	}
	printf("OpenXR extensions: %d\n", extentionPropCount);
	bool foundHeadless = false;
	for (uint32_t i = 0; i < extentionPropCount; ++i) {
		printf("\t%s\n", proparties[i].extensionName);
		if (strcmp(HEADLESS_EXT, proparties[i].extensionName) == 0)
			foundHeadless = true;
	}
	if (!foundHeadless) {
		puts("Runtime dose not support " HEADLESS_EXT);
		return 1;
	}

	const char *enabledExtensionNames[] = {HEADLESS_EXT, NULL};

	XrInstanceCreateInfo createInfo = {
		.type = XR_TYPE_INSTANCE_CREATE_INFO,
		.next = NULL,
		.createFlags = 0,
		.applicationInfo = applicationInfo,
		.enabledExtensionNames = enabledExtensionNames,
		.enabledExtensionCount = 1
	};

	XrSystemGetInfo getInfo = {
		.type = XR_TYPE_SYSTEM_GET_INFO,
		.formFactor = XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY
	};

	result = xrCreateInstance(&createInfo, &instance);
	if (XR_SUCCEEDED(result)) {
		printf("OpenXR instance created successfully.\n");
	} else {
		printf("Failed to create OpenXR instance: %d\n", result);
		return 1;
	}

	XrSystemId systemId;
	result = xrGetSystem(instance, &getInfo, &systemId);
	if (!XR_SUCCEEDED(result)) {
		printf("Failed to get OpenXR system: %s\n", xr_strerror(instance, result));
		return 1;
	}

	uint32_t viewCount;
	result = xrEnumerateViewConfigurationViews(instance, systemId, XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO, 0, &viewCount, NULL);
	XrViewConfigurationView* viewConfigs = calloc(viewCount, sizeof(XrViewConfigurationView));
	for (size_t i = 0; i < viewCount; ++i)
		viewConfigs[i].type = XR_TYPE_VIEW_CONFIGURATION_VIEW;
	if (XR_SUCCEEDED(result)) {
		result = xrEnumerateViewConfigurationViews(instance, systemId, XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO, viewCount, &viewCount, viewConfigs);
		if (!XR_SUCCEEDED(result)) {
			printf("Failed to enumerate viewConfigs: %d\n", result);
			return 1;
		}
	}

	XrSession session;
	XrSessionCreateInfo createSessionInfo = {
		.type = XR_TYPE_SESSION_CREATE_INFO,
		.systemId = systemId
	};
	result = xrCreateSession(instance, &createSessionInfo, &session);
	if (!XR_SUCCEEDED(result)) {
		printf("Failed to create session: %s\n", xr_strerror(instance, result));
		return 1;
	}
	XrSessionBeginInfo beginInfo = {.type = XR_TYPE_SESSION_BEGIN_INFO, .primaryViewConfigurationType = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO};
	result = xrBeginSession(session, &beginInfo);

	XrSpace stageSpace;
	XrReferenceSpaceCreateInfo spaceCreateInfo = {
		.type = XR_TYPE_REFERENCE_SPACE_CREATE_INFO,
		.referenceSpaceType = XR_REFERENCE_SPACE_TYPE_STAGE
	};
	spaceCreateInfo.poseInReferenceSpace.orientation.x = 1;
	result = xrCreateReferenceSpace(session, &spaceCreateInfo, &stageSpace);
	if (!XR_SUCCEEDED(result)) {
		printf("Failed to create referance space: %s\n", xr_strerror(instance, result));
		return 1;
	}

	struct timespec duration = {.tv_sec = 1};
	nanosleep(&duration, NULL);

	XrView *views = calloc(viewCount, sizeof(*views));
	for (size_t i = 0; i < viewCount; ++i)
		views[i].type = XR_TYPE_VIEW;
	XrViewState state = {.type = XR_TYPE_VIEW_STATE};

	signal(SIGTERM, handler);
	signal(SIGHUP, handler);
	signal(SIGINT, handler);

	while(!stop) {
		XrFrameWaitInfo waitInfo = {.type = XR_TYPE_FRAME_WAIT_INFO};
		XrFrameState frameState = {.type = XR_TYPE_FRAME_STATE};
		result = xrWaitFrame(session, &waitInfo, &frameState);
		if (!XR_SUCCEEDED(result)) {
			printf("Failed to wait for frame: %s\n", xr_strerror(instance, result));
			return 1;
		} else {
			printf("waited for frame time: %lu\n", frameState.predictedDisplayPeriod);
		}

		XrViewLocateInfo locateInfo = {
			.type = XR_TYPE_VIEW_LOCATE_INFO,
			.viewConfigurationType = XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO,
			.space = stageSpace,
			.displayTime = frameState.predictedDisplayTime+1
		};
		uint32_t locatedViews;
		result = xrLocateViews(session, &locateInfo, &state, viewCount, &locatedViews, views);
		if (!XR_SUCCEEDED(result)) {
			printf("Failed to locate views: %s\n", xr_strerror(instance, result));
			struct timespec duration = {.tv_nsec = 1000*100};
			nanosleep(&duration, NULL);
			continue;
		} else if (locatedViews != viewCount) {
			printf("Failed to locate all views");
			struct timespec duration = {.tv_nsec = 1000*100};
			nanosleep(&duration, NULL);
			continue;
		}

		clear();
		for (size_t i = 0; i < viewCount; ++i) {
			printf("View %zu:\n", i);
			printf("\tRecommended Size: %d x %d\n", viewConfigs[i].recommendedImageRectWidth, viewConfigs[i].recommendedImageRectHeight);
			printf("\tFOV:\n\t\tUP: %f\n\t\tDOWN: %f\n\t\tLEFT: %f\n\t\tRIGHT: %f\n", views[i].fov.angleUp, views[i].fov.angleDown, views[i].fov.angleLeft, views[i].fov.angleRight);
			printf("\tPOS:\n\t\tX: %f\n\t\tY: %f\n\t\tZ: %f\n", views[i].pose.position.x, views[i].pose.position.y, views[i].pose.position.z);
		}

		struct timespec duration = {.tv_nsec = 1000*100};
		nanosleep(&duration, NULL);
	}

	xrEndSession(session);
	free(views);
	free(viewConfigs);
	xrDestroySpace(stageSpace);
	xrDestroySession(session);
	xrDestroyInstance(instance);

	return 0;
}