#define _DEFAULT_SOURCE /* for getopt() and optarg */

#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 VERSION "0.0.1"

#define DEFAULT_DELAY_MS 30

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

const char *self;

int debugging = 0;                      /* -v */
const char *keyboard_dev = DEFAULT_KBD; /* -k */
int delay_ms = DEFAULT_DELAY_MS;        /* -d */

/* 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;
}

void print_help(void) {
	/* helptext comes from usage.c, which gets generated by mkusage.pl,
	   from the content in the the .rst file. */
	extern const char *helptext[];

	const char **helpline;

	puts("marsond " VERSION ", by B. Watson <urchlay@slackware.uk>, WTFPL");
	puts("Usage:");

	for(helpline = helptext; *helpline; helpline++)
		puts(*helpline);
}

void version(void) {
	puts(VERSION);
}

void parse_args(int argc, char **argv) {
	int opt;

	opterr = 0;

   if(argc >= 2) {
      if(strcmp(argv[1], "--help") == 0) {
         print_help();
         exit(0);
      } else if(strcmp(argv[1], "--version") == 0) {
         version();
         exit(0);
      }
   }

	while( (opt = getopt(argc, argv, "d:hk:vV")) != -1) {
		switch(opt) {
			case 'v': debugging++;             break;
			case 'd': delay_ms = atoi(optarg); break;
			case 'k': keyboard_dev = optarg;   break;
			case 'h': print_help(); exit(0);   break;
			case 'V': version(); exit(0);      break;
			case '?': die("invalid option (try --help)"); break;
			default:  print_help(); exit(1);              break;
		}
	}

	if(delay_ms < 1) die("invalid -d argument");
}

void daemonize(void) {
	int pid;

	pid = fork();
	if(pid < 0) {
		die("fork() failed");
	} else if(pid) {
		/* parent */
		exit(0);
	}

	/* we are the child here */
	setsid();

	pid = fork();
	if(pid < 0) {
		die("fork() failed");
	} else if(pid) {
		/* 2nd generation parent */
		info("forked to background, PID %d\n", pid);
		exit(0);
	}

	/* we are the grandchild here */
	chdir("/");
	close(0);
	close(1);
	close(2);
}

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

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

	parse_args(argc, argv);

	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));
		}
	}
	debug("UI_SET_KEYBIT OK");

	memset(&dev, 0, sizeof(dev));
	snprintf(dev.name, UINPUT_MAX_NAME_SIZE, "marsond virtual keyboard");
	dev.id.bustype = BUS_USB;
	dev.id.vendor =  0x69;
	dev.id.product = 0x666;
	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));
	}

	if(!debugging) daemonize();

	/* note: don't call die() unless debugging is true, since daemonize()
	   closes our stderr (there's nowhere for the error message to print). */

	while(1) {
		if(read(infd, &ev, sizeof(ev)) < 0) {
			if(debugging)
				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) {
			if(debugging)
				die("write to /dev/uinput failed: %s", strerror(errno));
		}
	}

	exit(1);
}

/*
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
*/