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

const char *bat_base_path = "/sys/class/power_supply/";
int dead = 0;

void usage (void)
{
	printf("usage: bmon [-wuh] [-f file] [-t interval]\n");
}

void int_handler (int signum)
{
        dead = 1;
}

int main (int argc, char *argv[])
{
	/* Handle SIGINT */
        dead = 0;
        struct sigaction action;
        memset(&action, 0, sizeof(action));
        action.sa_handler = int_handler;
        sigaction(SIGINT, &action, NULL);

	int wflag = 0;
	int wait_time = 10;
	int fflag = 0;
	int uflag = 0;
	char ofile_path[256];

	int opc;
	while ((opc = getopt(argc, argv, "uhwf:t:")) != -1) {
		switch (opc) {
		case 'w':
			wflag = 1;
			break;
		case 'f':
			fflag = 1;
			strncpy(ofile_path, optarg, 255);
			break;
		case 't':
			wait_time = atoi(optarg);
			if (wait_time < 1) {
				usage();
				exit(1);
			}
			break;
		case 'u':
			uflag = 1;
			break;
		case 'h':
		default: /* '?' */
			usage();
			exit(1);
		break;
		}

	}

	DIR *bdir = NULL;
	if (!(bdir = opendir(bat_base_path))) {
		perror("error opening base directory");
		exit(1);
	}

	struct dirent *ent = NULL;
	FILE **fp_list = NULL;
	int fp_num = 0;
	for (;;) {
		errno = 0;
		if (!(ent = readdir(bdir))) {
			if (errno) {
				perror("error reading base directory");
				exit(1);
			}
			else break;
		}

		if (!strstr(ent->d_name, "BAT1"))
			continue;

		FILE *fp;
		char path[sizeof(bat_base_path) + 256 + 64];
		strcpy(path, bat_base_path);
		strcat(path, ent->d_name);
		if (wflag) {
			char *tmp = malloc(1024);
			strcpy(tmp, path);
			strcat(tmp, "/status");
			FILE *tmf = fopen(tmp, "r");
			fgets(tmp, 1024, tmf);
			if (!strstr(tmp, "Dis")) {
				fprintf(stderr, "currently not discharging, cannot read power draw\n");
				dead = 1;
			}
			fclose(tmf);
			free(tmp);
			strcat(path, "/power_now");
		} else strcat(path, "/capacity");

		if ((fp = fopen(path, "r"))) {
			FILE **tmp = NULL;
			tmp = realloc(fp_list, sizeof(FILE *) * (fp_num + 1));
			if (!tmp)
				perror("failed realloc");
			fp_list = tmp;
			fp_list[fp_num++] = fp;
		} else printf("err: %s\n", strerror(errno));

	}
	closedir(bdir);
	if (!fp_num) {
		printf("no files were opened\n");
		dead = 1;
	}

	FILE * ofile_ptr = stdout;
	if (fflag) {
		if (!(ofile_ptr = fopen(ofile_path, "w"))) {
			char *tmp = malloc(1024);
			snprintf(tmp, 1024, "could not open %s", ofile_path);
			perror(tmp);
			free(tmp);
			exit(1);
		}
	}

	long int elapsed_time = 0;
	long val;
	char buf[64];
	for (; !dead ; sleep(wait_time)) {
		for (int i = 0; i < fp_num; i++) {
			if (!freopen(NULL, "r", fp_list[i])) {
				perror("error reading the file");
				dead = 1;
			}
			if (!fgets(buf, 64, fp_list[i]))
				dead = 1;
			val = atol(buf);
			fprintf(ofile_ptr, "%ld\t", wflag ? (long)(val / 1E3) : val);
		}
		fprintf(ofile_ptr, "%ld\n", uflag ? time(NULL) : elapsed_time);
		if (fflush(ofile_ptr)) {
			perror("error writing to file");
			dead = 1;
		}
		elapsed_time += wait_time;
	}

	if (fflag)
		fclose(ofile_ptr);
	for (int i = 0; i < fp_num; i++)
		fclose(fp_list[i]);
	free(fp_list);
	return 0;
}