#pragma once 

#include <limits.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>

int getpstartts(int pid, unsigned long long* startts) {
	char path[255], fc[1024];
	char* ptr = fc;

	snprintf(path, sizeof(path), "/proc/%d/stat", pid);
	int fd = open(path, O_RDONLY);

	if (fd < 0)
		err(1, "Could not open %s", path);

	int bytes_read = read(fd, fc, sizeof(fc));
	close(fd);

	if (memchr(ptr, '\0', bytes_read) != NULL)
		return -1;
	
	ptr = strrchr(fc, ')');
	
	char* token = strtok(ptr, " ");

	for (short i = 0; i<20 && token; i++)
		token = strtok(NULL, " ");

	if (!token)
		return -1;

	unsigned long long temp_ts = strtoull(token, NULL, 10);
	if (temp_ts == 0 || temp_ts == ULLONG_MAX)
		return -1;

	*startts = temp_ts;
	return 0;
}

int gethandle(int recur) {
	if (recur >= 2)
		errx(1, "Too many recursions in gethandle()");

	struct stat st;
	int fd = open("/run/rdo", O_RDONLY, O_DIRECTORY | O_NOFOLLOW);

	if (fd < 0) {
		if (errno == ENOENT) {
			if (mkdir("/run/rdo", 0700) < 0)
				err(1, "Could not create /run/rdo");
			return gethandle(++recur);
		}
		else
			err(1, "Could not open /run/rdo");
	} else {
		if (fstat(fd, &st) < 0)
			err(1, "Could not fstat /run/rdo");

		if (st.st_uid != 0 || st.st_mode != (0700 | S_IFDIR))
			return -1;
	}

	return fd;
}

void setsession(int pid, unsigned int ts_ttl) {
    if (ts_ttl == 0)
        return;

    unsigned long long startts;
	char path[1024], ts_str[32];

	int dirfd = gethandle(0);
	if (dirfd < 0 && errno == 0)
		return;
	
	if (getpstartts(pid, &startts) < 0)
		return;

	snprintf(path, sizeof(path), "/run/rdo/%d-%llu", pid, startts);

	int fd = openat(dirfd, path, O_CREAT | O_EXCL | O_WRONLY, 0700);
	if (fd < 0) {
		if (errno == EEXIST)
			return;
		err(1, "Could not open %s", path);
	}
	
    snprintf(ts_str, sizeof(ts_str), "%llu", (unsigned long long)time(NULL));

    if (write(fd, ts_str, strlen(ts_str)) < 0)
        err(1, "Could not write to %s", path);

    close(fd);

	return;
}

int getsession(int pid, unsigned int ts_ttl) {
    if (ts_ttl == 0)
        return -1;

    unsigned long long startts, current;
	char path[1024], ts_str[32];

    int dirfd = gethandle(0);
	if (dirfd < 0 && errno == 0)
		return -1;

	if (getpstartts(pid, &startts) < 0)
		return -1;

    snprintf(path, sizeof(path), "/run/rdo/%d-%llu", pid, startts);

	int fd = openat(dirfd, path, O_RDONLY);
    if (fd < 0) {
        if (errno == ENOENT)
            return -1;
        err(1, "Could not open %s", path);
    }

    if (read(fd, ts_str, sizeof(ts_str)) < 0)
        err(1, "Could not read %s", path);

    startts = strtoull(ts_str, NULL, 10);
    current = time(NULL);

    if (current - startts > ts_ttl) {
        unlink(path);
        return -1;
    }

    return 0;
}