#define _POSIX_C_SOURCE 200809L
#define _DEFAULT_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <X11/Xlib.h>

#define ELEMENT_NUMBER 2
#define CHARS 64
#define SEPARATOR " | "
#define BAR_LENGTH (CHARS - (ELEMENT_NUMBER - 1) * sizeof(SEPARATOR))
#define ELEMENT_SIZE (BAR_LENGTH / ELEMENT_NUMBER)
/* ANSI colors escape codes */
#define ANSI_COLOR_RED     "\x1b[31m"
#define ANSI_COLOR_GREEN   "\x1b[32m"
#define ANSI_COLOR_YELLOW  "\x1b[33m"
#define ANSI_COLOR_BLUE    "\x1b[34m"
#define ANSI_COLOR_MAGENTA "\x1b[35m"
#define ANSI_COLOR_CYAN    "\x1b[36m"
#define ANSI_COLOR_RESET   "\x1b[0m"

const char bat_base_dir[] = "/sys/class/power_supply/";

struct battery_descriptor {
	int f_cap; /* Capacity file pointer */
	int f_stat; /* Status file pointer */
};

static const char * get_date (void);
static const char * get_battery (void);
static void die (const char *, ...);

int main (void)
{
	static int screen;
	static Display *dpy = NULL;
	static Window root;
	static char bar[BAR_LENGTH] = {0};

	dpy = XOpenDisplay(NULL);
	if (!dpy)
		die("cannot open default display");
	screen = DefaultScreen(dpy);
	root = RootWindow(dpy, screen);

	// TODO: do not use sleep instead poll file desciptors for a change
	for (;;sleep(10)) {
		if (snprintf(bar, BAR_LENGTH, "%s" SEPARATOR "%s", get_battery(), get_date()) > BAR_LENGTH)
			bar[BAR_LENGTH - 1] = '\0';

		XStoreName(dpy, root, bar);
		XSync(dpy, False);
	}
	
	XCloseDisplay(dpy);
	return 0;
}

static const char * get_date (void)
{
	static char str[ELEMENT_SIZE] = {0};
	static time_t rawtime;
	time(&rawtime);
	strftime(str, ELEMENT_SIZE, "%a %d %b %H:%M", localtime(&rawtime));
	return str;
}

#if defined( __linux__ )
static const char * get_battery (void) {
	static char str[ELEMENT_SIZE] = {0};
	static int init = 1;
	static struct battery_descriptor *bat_arr = NULL;
	static int bat_num = 0;
	static char buf[sizeof(bat_base_dir) + 256 + 64];

	if (init) {
		DIR *bdir;
		struct dirent *dent = NULL;
		int tmpf;
		
		if (!(bdir = opendir(bat_base_dir)))
			die("error opening %s", bat_base_dir);
		while (1) {
			errno = 0;
			if (!(dent = readdir(bdir))) {
				if (errno)
					die("error reading %s", bat_base_dir);
				else
					break;
			}
		/*	if (dent->d_type != DT_DIR)
				continue;*/
			if (!strstr(dent->d_name, "BAT"))
				continue;

			bat_arr = realloc(bat_arr, sizeof(struct battery_descriptor) * ++bat_num);
			if(!bat_arr)
				die("bad realloc in get_battery");

			strcpy(buf, bat_base_dir);
			strcat(buf, dent->d_name);
			strcat(buf, "/capacity");
			if ((tmpf = open(buf, O_RDONLY | O_NONBLOCK)) < 0)
				die("error opening %s", buf);
			bat_arr[bat_num - 1].f_cap = tmpf;

			strcpy(buf, bat_base_dir);
			strcat(buf, dent->d_name);
			strcat(buf, "/status");
			if ((tmpf = open(buf, O_RDONLY | O_NONBLOCK)) < 0)
				die("error opening %s", buf);
			bat_arr[bat_num - 1].f_stat = tmpf;
		}
		closedir(bdir);
		if (!bat_arr)
			die("no batteries were found");
		init = 0;
	}
	memset(str, 0, ELEMENT_SIZE);
	int cap = 0;
	int level = 0;
	int barsize = 0;
	int charging = 0;
	for (int i = 0; i < bat_num; i++) {
		memset(buf, 0, sizeof(bat_base_dir) + 256 + 64);
		pread(bat_arr[i].f_cap, buf, 64, 0);
		cap = atoi(buf);
		barsize = (ELEMENT_SIZE / bat_num) - 5 - strlen(buf);
		level = (cap / 100.0) * barsize;
		pread(bat_arr[i].f_stat, buf, 64, 0);
		charging = strstr(buf, "Dis") ? 0 : 1;

		strcat(str, "[");
		for (int i = 0; i < level; i++)
			strcat(str, charging ? "+" : "=");
		for (int i = 0; i < barsize - level; i++)
			strcat(str, " ");
		snprintf(buf, 64, "] %d%%", cap);
		strcat(str, buf);
	}
	return str;
}
#elif defined( __OpenBSD__ )
static const char * get_battery (void) {
    return "not supported";
}
#endif

void die(const char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);

	fputs(ANSI_COLOR_RED, stderr);
     	vfprintf(stderr, fmt, ap);

	if (fmt[0] && fmt[strlen(fmt) - 1] == ':') {
		fputc(' ', stderr);
		perror(NULL);
	} else {
		fputc('\n', stderr);
	}
     	fputs(ANSI_COLOR_RESET, stderr);

	va_end(ap);
	exit(errno ? errno : 1);
}