#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdarg.h>

#include <linux/input.h>
#include <linux/uinput.h>

#define DELAY_MS 30

#define DEFAULT_KBD "/dev/input/by-id/usb-Marson_Marson_Keyboard_and_Mouse_Link_Ver:ps2120L-event-kbd"

/* eventually, this will take options to set the device and
	delay for the Enter key, and will have an rc script to
	start it...? */

const char *self;

int debugging = 1;

const char *keyboard_dev;

/* variadic macros are apparently C99 and not just a GNU extension */
void logmsg(const char *prefix, const char *fmt, ...) {
	va_list ap;
	va_start(ap, fmt);
	fprintf(stderr, "%s: %s: ", self, prefix);
	vfprintf(stderr, fmt, ap);
	va_end(ap);
	fputc('\n', stderr);
}

#define die(fmt,  ...)  { logmsg("fatal",   fmt, ##__VA_ARGS__); exit(1); };
#define warn(fmt, ...)  logmsg("warning", fmt, ##__VA_ARGS__);
#define info(fmt, ...)  logmsg("info",    fmt, ##__VA_ARGS__);
#define debug(fmt, ...) { if(debugging) logmsg("debug",    fmt, ##__VA_ARGS__); };

void set_self(const char *argv0) {
   char *p;
   self = argv0;
   p = strrchr(self, '/');
   if(p) self = p + 1;
}

int main(int argc, char **argv) {
	int infd, outfd, i;
	struct uinput_user_dev dev;
	struct input_event ev;
	static struct input_event deferred_ev;

	set_self(argv[0]);
	debug("starting up");

	if(!keyboard_dev)
		keyboard_dev = DEFAULT_KBD;

	if((outfd = open("/dev/uinput", O_WRONLY | O_NONBLOCK)) >= 0) {
		debug("opened /dev/uinput");
	} else {
		die("failed to open /dev/uinput: %s", strerror(errno));
	}

	if((infd = open(keyboard_dev, O_RDONLY)) >= 0) {
		debug("opened %s", keyboard_dev);
	} else {
		die("failed to open %s: %s", keyboard_dev, strerror(errno));
	}

	if(ioctl(infd, EVIOCGRAB, 1) >= 0) {
		debug("grabbed %s", keyboard_dev);
	} else {
		die("failed to grab %s: %s", keyboard_dev, strerror(errno));
	}

	if(ioctl(outfd, UI_SET_EVBIT, EV_KEY) >= 0) {
		debug("UI_SET_EVBIT OK");
	} else {
		die("UI_SET_EVBIT failed: %s", strerror(errno));
	}

	for(i = 0; i < KEY_MAX; i++) {
		if(ioctl(outfd, UI_SET_KEYBIT, i) >= 0) {
			/* we don't wanna be *that* verbose */
		} else {
			die("UI_SET_EVBIT failed: %s", strerror(errno));
		}
	}

	memset(&dev, 0, sizeof(dev));
	snprintf(dev.name, UINPUT_MAX_NAME_SIZE, "marsond virtual keyboard");
	dev.id.bustype == BUS_USB;
	dev.id.vendor = 1;
	dev.id.product = 1;
	dev.id.version = 1;

	if(write(outfd, &dev, sizeof(dev)) >= 0) {
		debug("wrote dev structure to /dev/uinput");
	} else {
		die("write to /dev/uinput failed: %s", strerror(errno));
	}

	if(ioctl(outfd, UI_DEV_CREATE) >= 0) {
		debug("created virtual keyboard device");
	} else {
		die("UI_DEV_CREATE failed: %s", strerror(errno));
	}

	while(1) {
		if(read(infd, &ev, sizeof(ev)) < 0) {
			die("read from %s failed: %s", keyboard_dev, strerror(errno));
		}

		debug("event: type %d, code %d, value %d\n",
				ev.type, ev.code, ev.value);

		if(ev.type == EV_KEY && ev.code == KEY_ENTER && ev.value == 0) {
			debug("got Enter key release, delaying %d ms", DELAY_MS);
			usleep(DELAY_MS * 1000);
		}

		if(write(outfd, &ev, sizeof(ev)) < 0) {
			die("write to /dev/uinput failed: %s", strerror(errno));
		}
	}

	exit(0);
}

/*
for the A key:

event: type 4, code 4, value 458756
event: type 1, code 30, value 1
event: type 0, code 0, value 0
event: type 4, code 4, value 458756
event: type 1, code 30, value 0
event: type 0, code 0, value 0

for Enter:

event: type 4, code 4, value 458792
event: type 1, code 28, value 1
event: type 0, code 0, value 0
event: type 4, code 4, value 458792
event: type 1, code 28, value 0
event: type 0, code 0, value 0
*/