#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>

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

void usage (void)
{
	printf("usage: bmon [-h] [-w] [-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;
	char ofile_path[256];

	int opc;
	while ((opc = getopt(argc, argv, "hwf: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 < 0) {
				usage();
				exit(1);
			}
			break;
		case 'h':
		default: /* '?' */
			usage();
			exit(1);
		break; 
		}
		
	}

	DIR *bdir = NULL;
	if (!(bdir = opendir(bat_base_path)))
		perror("error opening base directory");
	
	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");
			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)
			strcat(path, "/energy_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");
		goto main_end;
	}
	
	FILE * ofile_ptr;
	if (fflag) {
		if (!(ofile_ptr = fopen(ofile_path, "w"))) {
			char * tmp = malloc(1024);
			snprintf(tmp, 1024, "could not open %s", ofile_path);
			perror(tmp);
		}
	}

	long long elapsed_time = 0;
	char buf[64];
	for (; !dead ; sleep(wait_time)) {
		for (int i = 0; i < fp_num; i++) {
			freopen(NULL, "r", fp_list[i]);
			fgets(buf, 64, fp_list[i]);
			buf[strcspn(buf, "\r\n")] = 0;
			if (fflag)
				fprintf(ofile_ptr, "%s\t", buf);
			else
				printf("%s\t", buf);
		}
		if (fflag) {
			fprintf(ofile_ptr, "%lld\n", elapsed_time);
			fflush(ofile_ptr);
		} else { 
			printf("%lld\n", elapsed_time);
		}
		elapsed_time += wait_time;
	}
	
	main_end:
	if (fflag)
		fclose(ofile_ptr);
	for (int i = 0; i < fp_num; i++)
		fclose(fp_list[i]);
	free(fp_list);
	return 0;
}