#define _BSD_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <strings.h>
#include <sys/time.h>
#include <time.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <X11/Xlib.h>

#define BASE "/sys/class/power_supply/BAT0"

static Display *dpy;

char *
smprintf(char *fmt, ...)
{
	va_list fmtargs;
	char *ret;
	int len;

	va_start(fmtargs, fmt);
	len = vsnprintf(NULL, 0, fmt, fmtargs);
	va_end(fmtargs);

	ret = malloc(++len);
	if (ret == NULL) {
		perror("malloc");
		exit(1);
	}

	va_start(fmtargs, fmt);
	vsnprintf(ret, len, fmt, fmtargs);
	va_end(fmtargs);

	return ret;
}

char *
readfile(const char *base, const char *file)
{
	char *path, line[513];
	FILE *fd;

	memset(line, 0, sizeof(line));

	path = smprintf("%s/%s", base, file);
	fd = fopen(path, "r");
	if (fd == NULL)
		return NULL;
	free(path);

	if (fgets(line, sizeof(line)-1, fd) == NULL)
		return NULL;
	fclose(fd);

	return smprintf("%s", line);
}

char
statussymbol(const char *base)
{
	char *co;

	co = readfile(base, "status");
	if (co == NULL)
		return 'f';
	else if (!strncmp(co, "Charging", 8))
		return '+';
	else if (!strncmp(co, "Discharging", 11))
		return '-';
	else
		return '=';

	free(co);
}

/*
 * Linux seems to change the filenames after suspend/hibernate
 * according to a random scheme. So just check for both possibilities.
 */
char *
getbattery(const char *base)
{
	char *co;
	int descap, remcap;

	descap = -1;
	remcap = -1;

	co = readfile(base, "present");
	if (co == NULL || co[0] != '1') {
		if (co != NULL) free(co);
		return smprintf("not present");
	}
	free(co);

	co = readfile(base, "charge_full");
	if (co == NULL) {
		co = readfile(base, "energy_full");
		if (co == NULL)
			return smprintf("");
	}
	sscanf(co, "%d", &descap);
	free(co);

	co = readfile(base, "charge_now");
	if (co == NULL) {
		co = readfile(base, "energy_now");
		if (co == NULL)
			return smprintf("");
	}
	sscanf(co, "%d", &remcap);
	free(co);

	if (remcap < 0 || descap < 0)
		return smprintf("invalid");

	return smprintf("%.0f%c",
			((float)remcap / (float)descap) * 100,
			statussymbol(base));
}

char *
mktimes(char *fmt)
{
	char buf[129];
	time_t tim;
	struct tm *timtm;

	memset(buf, 0, sizeof(buf));
	tim = time(NULL);
	timtm = localtime(&tim);
	if (timtm == NULL) {
		perror("localtime");
		exit(1);
	}

	if (!strftime(buf, sizeof(buf)-1, fmt, timtm)) {
		fprintf(stderr, "strftime == 0\n");
		exit(1);
	}

	return smprintf("%s", buf);
}

void
setstatus(char *str)
{
	XStoreName(dpy, DefaultRootWindow(dpy), str);
	XSync(dpy, False);
}

int
main(void)
{
	char *batt;
	char *stat;
	char *time;

	if (!(dpy = XOpenDisplay(NULL))) {
		fprintf(stderr, "dwmstatus: cannot open display.\n");
		return 1;
	}

	for (;;sleep(90)) {
		batt = getbattery(BASE);
		time = mktimes("%a %d %b %H:%M");

		stat = smprintf("%s %s", time, batt);

		setstatus(stat);

		free(batt);
		free(stat);
		free(time);
	}

	XCloseDisplay(dpy);

	return 0;
}