#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <assert.h>
#include <string.h>
#include <time.h>
#include <getopt.h>
#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <X11/Xproto.h>
#include <X11/Xutil.h>

struct status{
	Display *dpy;
	Window root;
	char status[256];
	const char *time_format;
	unsigned int status_update_interval;
};

struct sigaction *s_act = NULL;
struct status *current_status_ptr = NULL;
XTextProperty *status_props_ptr = NULL;

void sighandler( int si_code, siginfo_t *si_info, void *si_adr ){
	int exit_status = EXIT_SUCCESS;
	if ( si_code == SIGSEGV ){
		fprintf( stderr, "error: SIGSEGV received: %s\n", strerror(errno) );
		exit_status = EXIT_FAILURE;
	}
	else
	{
		fprintf( stdout, "Received signal %i, exiting\n", si_code );
	}
	if ( current_status_ptr->dpy != NULL ){
		if ( XCloseDisplay(current_status_ptr->dpy) == BadGC )
			fputs( "XCloseDisplay returned BadGC error\n", stderr );
		current_status_ptr->dpy = NULL;
	}
	memset( (void*)status_props_ptr, 0, sizeof(*status_props_ptr) );
	free( s_act );
	s_act = NULL;
	exit( exit_status );
}

void update_status( struct status *status_info, XTextProperty *xprops ){
	if ( status_info == NULL || xprops == NULL )
		return;
	XSetTextProperty( status_info->dpy, status_info->root, xprops, XA_WM_NAME );
	XSync( status_info->dpy, 0 );
	return;
}

void status_update_loop( struct status *cstatus, XTextProperty *status_properties ){
	if ( cstatus == NULL || status_properties == NULL ){
		fputs( "error: status struct pointer is NULL\n", stderr );
		return;
	}
	time_t current_time = 0;
	struct tm *time_info = NULL;
	while ( 1 ){
		memset( (void*)&cstatus->status, 0, sizeof(cstatus->status) * sizeof(char) );
		current_time = time( NULL );
		time_info = localtime( (const time_t*)&current_time );
		if ( (status_properties->nitems = (unsigned long)strftime((char*)&cstatus->status, (sizeof(cstatus->status) * sizeof(char)) - 1, cstatus->time_format, time_info)) <= 0 ){
			sleep( cstatus->status_update_interval );
			continue;
		}
		update_status( cstatus, status_properties );
		sleep( cstatus->status_update_interval );
	}
	return;
}

int main( int argc, char **args ){
	if ( argc < 5 ){
		fprintf( stdout, "Usage: %s -i [update interval in seconds] -d [display] -f [time format]\n", args[0] );
		exit( EXIT_SUCCESS );
	}
	s_act = (struct sigaction*)calloc( 1, sizeof(struct sigaction) );
	if ( s_act == NULL ){
		perror( "sigaction struct allocation failed" );
		exit( EXIT_FAILURE );
	}
	if ( sigemptyset(&s_act->sa_mask) == -1 ){
		perror( "failed to create empty sigset" );
		free( s_act );
		exit( EXIT_FAILURE );
	}
	s_act->sa_flags = SA_SIGINFO;
	s_act->sa_sigaction = &sighandler;
	if ( sigaction(SIGABRT, (const struct sigaction*)s_act, NULL) == -1 ){
		perror( "failed to set SIGABRT handler" );
		free( s_act );
		exit( EXIT_FAILURE );
	}
	assert( sigaction(SIGSEGV, (const struct sigaction*)s_act, NULL) != -1 );
	assert( sigaction(SIGINT, (const struct sigaction*)s_act, NULL) != -1 );
	assert( sigaction(SIGTERM, (const struct sigaction*)s_act, NULL) != -1 );
	assert( sigaction(SIGPIPE, (const struct sigaction*)s_act, NULL) != -1 );
	struct status current_status = {0};
	memset( (void*)&current_status, 0, sizeof(struct status) );
	XTextProperty status_props = {
		.value = (unsigned char*)&current_status.status,
		.encoding = XA_STRING,
		.format = 8,
		.nitems = 0
	};
	const char *optstring = "i:d:f:";
	int opt_char = 0;
	while ( (opt_char = getopt(argc, args, optstring)) != -1 ){
		switch (opt_char){
			case 'i':
				current_status.status_update_interval = (unsigned int)strtoull( optarg, NULL, 10 );
				assert( errno == 0 );
				break;
			case 'd':
				current_status.dpy = XOpenDisplay( (_Xconst char*)optarg );
				assert( current_status.dpy != NULL );
				break;
			case 'f':
				current_status.time_format = (const char*)optarg;
				assert( current_status.time_format != NULL && strlen(current_status.time_format) > 0 );
				break;
			default:
				break;
		}
	}
	current_status.root = DefaultRootWindow( current_status.dpy );
	current_status_ptr = &current_status;
	status_props_ptr = &status_props;
	status_update_loop( &current_status, &status_props );
	exit( EXIT_SUCCESS );
}