#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <sys/types.h>
#include <regex.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <Xutil.h>
#include <Xatom.h>

#define BATTERY "BAT1"
#define BATT_INFO_PATH  "/proc/acpi/battery/"BATTERY"/info"
#define BATT_STATE_PATH "/proc/acpi/battery/"BATTERY"/state"
#define BATT_FULL_REGEX "^last full capacity:[ ]+([0-9]*) .*$"
#define BATT_CUR_REGEX  "^remaining capacity:[ ]+([0-9]*) .*$"
#define DATE_FORMAT "%H:%M (%Z) - %a %d.%m.%Y"
#define BUFFER_SIZE 4096
#define STATUS_SIZE 256

static char *buf;
static regex_t *batt_full_re, *batt_cur_re;
static Display *dpy;
static Window root;
static XTextProperty name;

void update_status(char *c) {
	name.value=(unsigned char*)c;
	name.nitems=strlen(c);
	XSetWMName(dpy, root, &name);
	XSync(dpy, False);
}

void cleanup(void) {
	regfree(batt_full_re);
	regfree(batt_cur_re);
	free(buf);
}

void die(int unused) {
	update_status("dwmrc died!");
	exit(EXIT_FAILURE);
}

int read_batt(const char *batt_path, const regex_t *batt_re) {
	FILE *f;
	int batt_total = -1;
	regmatch_t result_re[2];

	f = fopen(batt_path, "r");
	fread(buf, 1, BUFFER_SIZE, f);
	regexec(batt_re, buf, 2, result_re, 0);
	if(result_re[1].rm_so != -1 && result_re[1].rm_eo != -1) {
		buf[result_re[1].rm_eo]='\0';
		batt_total = atoi(buf+result_re[1].rm_so);
	}
	fclose(f);
	return batt_total;
}

int main(int argc, char **argv) {
	time_t cur_t;
	struct tm *cur_lt;
	char *status;
	int batt_full, batt_cur;
	int n;

	if( !(dpy = XOpenDisplay(NULL)) ||
		!(buf = calloc(1, sizeof(char)*BUFFER_SIZE)) ||
		!(status = calloc(1, sizeof(char)*STATUS_SIZE)) ||
		!(batt_full_re = calloc(1, sizeof(regex_t))) ||
		!(batt_cur_re = calloc(1, sizeof(regex_t))) ) die(0);

	regcomp(batt_full_re, BATT_FULL_REGEX, REG_EXTENDED|REG_NEWLINE);
	regcomp(batt_cur_re,  BATT_CUR_REGEX, REG_EXTENDED|REG_NEWLINE);

	root = RootWindow(dpy, DefaultScreen(dpy));
	name.encoding=XA_STRING;
	name.format=8;

	signal(SIGINT, die);
	signal(SIGILL, die);
	signal(SIGTERM, die);

	while(1) {
		batt_full=read_batt(BATT_INFO_PATH, batt_full_re);
		batt_cur =read_batt(BATT_STATE_PATH, batt_cur_re);

		if(batt_full > 0 && batt_cur >= 0) n=snprintf(status, STATUS_SIZE, "%3d%% -- ", (100*batt_cur/batt_full));
		else n=snprintf(status, STATUS_SIZE, " NAN -- ");

		cur_t = time(NULL);
		cur_lt = localtime(&cur_t);
		strftime(&status[n], STATUS_SIZE-n, DATE_FORMAT, cur_lt);
		update_status(status);

		sleep(10);
	}

	return EXIT_SUCCESS;
}