#include <linux/types.h>
#include <linux/input.h>
#include <linux/hidraw.h>
#include <linux/uinput.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdbool.h>

#define MAX_DEVICE_NAME_LEN 256
#define MAX_REPORT_LEN 128
#define VIVE_PRO_VID 0x0bb4
#define VIVE_PRO_PID 0x0309

typedef enum
{
	VIVE_PRO_BTN_NONE = 0,
	VIVE_PRO_BTN_VOL_UP = 0b1,
	VIVE_PRO_BTN_VOL_DOWN = 0b10,
	VIVE_PRO_BTN_MIC_MUTE = 0b100,
} vive_pro_btn_t;

static int open_vive_pro_hidraw(const char *device)
{
	int fd = open(device, O_RDWR);
	if (fd < 0) {
		perror("Unable to open device");
		return -1;
	}

	char device_name[MAX_DEVICE_NAME_LEN];
	int res = ioctl(fd, HIDIOCGRAWNAME(MAX_DEVICE_NAME_LEN), device_name);
	if (res < 0)
		perror("Unable to read device name");
	else
		printf("Connected to device: %s\n", device_name);

	struct hidraw_devinfo info;
	res = ioctl(fd, HIDIOCGRAWINFO, &info);
	if(res < 0)
	{
		perror("Unable to get device info");
		return -2;
	}
	else if (info.vendor != VIVE_PRO_VID || info.product != VIVE_PRO_PID)
	{
		fprintf(stderr, "%s is not a vive pro\n", device);
		return -3;
	}
	return fd;
}

static int register_uinput_device(const char* uinputdev, const char* devname, uint16_t vid, uint16_t pid)
{
	int fd = open(uinputdev, O_RDWR);
	if(fd < 0)
		return fd;

	struct uinput_setup dev = {};
	size_t len = strlen(devname);
	if(len > UINPUT_MAX_NAME_SIZE)
		len = UINPUT_MAX_NAME_SIZE;
	strncpy(dev.name, devname, len);

	dev.id.bustype = BUS_VIRTUAL;
	dev.id.vendor = vid;
	dev.id.product = pid;

	ioctl(fd, UI_SET_EVBIT, EV_KEY);
	ioctl(fd, UI_SET_KEYBIT, KEY_VOLUMEUP);
	ioctl(fd, UI_SET_KEYBIT, KEY_VOLUMEDOWN);
	ioctl(fd, UI_SET_KEYBIT, KEY_MICMUTE);

	int ret = ioctl(fd, UI_DEV_SETUP, &dev);
	if(ret < 0)
	{
		close(fd);
		return ret;
	}
	ret = ioctl(fd, UI_DEV_CREATE);
	if(ret < 0)
	{
		close(fd);
		return ret;
	}

	return fd;
}

struct vive_key_state
{
	bool volup;
	bool voldown;
	bool micmute;
};

static int send_keys(struct vive_key_state* state, int uinput_fd, uint8_t keys)
{
	struct input_event ev = {};
	bool syn = false;

	bool volup = keys & VIVE_PRO_BTN_VOL_UP;
	if(volup != state->volup)
	{
		ev.type = EV_KEY;
		ev.code = KEY_VOLUMEUP;
		ev.value = volup;
		state->volup = volup;
		if(write(uinput_fd, &ev, sizeof(ev)) != sizeof(ev))
			return -1;
		syn = true;
	}

	bool voldown = keys & VIVE_PRO_BTN_VOL_DOWN;
	if(voldown != state->voldown)
	{
		ev.type = EV_KEY;
		ev.code = KEY_VOLUMEDOWN;
		ev.value = voldown;
		state->voldown = voldown;
		if(write(uinput_fd, &ev, sizeof(ev)) != sizeof(ev))
			return -1;
		syn = true;
	}

	bool micmute = keys & VIVE_PRO_BTN_MIC_MUTE;
	if(micmute != state->micmute)
	{
		ev.type = EV_KEY;
		ev.code = KEY_MICMUTE;
		ev.value = micmute;
		state->micmute = micmute;
		if(write(uinput_fd, &ev, sizeof(ev)) != sizeof(ev))
			return -1;
		syn = true;
	}

	if(syn)
	{
		gettimeofday(&ev.time, NULL);
		ev.type = EV_SYN;
		ev.code = SYN_REPORT;
		ev.value = 0;
		if(write(uinput_fd, &ev, sizeof(ev)) != sizeof(ev))
			return -2;
	}
	return 0;
}

int main(int argc, char **argv)
{
	int res;

	char *device;
	if(argc > 1)
	{
		device = argv[1];
	}
	else
	{
		if(argc > 0)
			fprintf(stderr, "Usage: %s [VIVE PRO HIDRAW DEVICE]\n", argv[0]);
		return 1;
	}

	int hidraw_fd = open_vive_pro_hidraw(device);
	if(hidraw_fd < 0)
		return abs(hidraw_fd);

	int uinput_fd = register_uinput_device("/dev/uinput", "VIVE PRO", VIVE_PRO_VID, VIVE_PRO_PID);
	if(uinput_fd < 0)
	{
		perror("Unable to register uninput device\n");
		return abs(uinput_fd);
	}

	uint8_t buffer[MAX_REPORT_LEN];
	struct vive_key_state state = {};
	while((res = read(hidraw_fd, buffer, MAX_REPORT_LEN)) >= 0)
	{
		send_keys(&state, uinput_fd, buffer[9]);
	}

	close(hidraw_fd);
	close(uinput_fd);
	return 0;
}