#define _GNU_SOURCE
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sched.h>
#include <sys/syscall.h>
#include <linux/sched.h>
#include <stdarg.h>
#include <time.h>
#include <limits.h>
#include <signal.h>

#include "util.h"

struct params {
    char* shared_folder;
    int fd[2];
    int out_fd;
    char **argv;
};

struct limits {
    size_t memory;
    int core;
    int time;
};

struct killparams{
    int time;
    int pid;
};

#define READ_SIZE 100
char read_buf[READ_SIZE + 1];

#include "ns_exec.c"
#include "cgroup_prepare.c"

//time limit realisation
static int killafter(void *arg) {
    //die when parent dies
    if (prctl(PR_SET_PDEATHSIG, SIGKILL)) die("cannot PR_SET_PDEATHSIG for child process: %m\n");
    struct killparams* params = (struct killparams*) arg;
    struct timespec tw = {params -> time / 1000, ((params->time) % 1000) * 1000000};
    struct timespec tr;
    nanosleep(&tw, &tr);
    kill(params->pid, SIGKILL);
}

#define STACK_SIZE 1000000
static char nmstack[STACK_SIZE];
static char killstack[STACK_SIZE];

static void parse_args(int argc, char **argv, struct params *params,struct limits *limits){
    if (argc < 6) {
        puts("usage:\n starter <core_id> <memory_amount> <time limit in ms> <shared folder> <command, arg1,arg2,...>");
        exit(0);
    }
    argc--; argv++;
    limits->core = atoi(argv[0]);
    argc--; argv++;
    limits->memory = atoi(argv[0]);
    argc--; argv++;
    limits->time = atoi(argv[0]);
    argc--; argv++;
    params->shared_folder = argv[0];
    argc--; argv++;

    params->argv = argv;
}

//setup user namespace
static void prepare_userns(int pid) {
    char path[100];
    char line[100];

    int uid = 0;//root
    int gid = 0;//root
    int unprivileged_uid = 66534;//nobody
    int unprivileged_gid = 65534;//nogroup

    sprintf(path, "/proc/%d/uid_map", pid);
    sprintf(line, "0 %d 1\n1 %d 1000\n", uid, unprivileged_uid);//map root to uid 0,nobody to uid 1000
    write_file(path, line);

    sprintf(path, "/proc/%d/setgroups", pid);
    sprintf(line, "deny");
    write_file(path, line);

    sprintf(path, "/proc/%d/gid_map", pid);
    sprintf(line, "0 %d 1\n1 %d 1000\n", gid, unprivileged_gid);//map root to gid 0,nogroup to gid 1000
    write_file(path, line);
}

int main(int argc,char** argv) {
    if(setuid(0)) die("need to be run as root");
    if(setgid(0)) die("need to be run as root");
    //get binary folder
    char bin_path[PATH_MAX];
    if (realpath (argv[0], bin_path) == 0) die("unable to resolve real path: %m");//get absolute path to executable
    for(int i = strlen(bin_path); i > 0 && bin_path[i] != '/';i--) bin_path[i]=0;//cut filename to get directory name
    if(chdir(bin_path)) die("unable to chdir to binary path: %m");
    //set random seed
    srand(time(NULL));
    //setup parameters
    struct params params;
    memset(&params, 0, sizeof(struct params));
    struct limits limits;
    memset(&limits, 0, sizeof(struct limits));
    parse_args(argc, argv, &params, &limits);
    prepare_cgroup(&limits);
    if (pipe(params.fd) < 0) die("can't open pipe: %m");//a pipe to report readiness
    int clone_flags = SIGCHLD | CLONE_NEWUTS | CLONE_NEWUSER | CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWCGROUP;
    int nsrun_pid = clone(nsrun, nmstack + STACK_SIZE, clone_flags, &params);//make new namespace
    int pipe = params.fd[1];
    prepare_userns(nsrun_pid);
    if (nsrun_pid < 0) die("faled to clone");
    add_to_cgroup(nsrun_pid);
    if (write(pipe, "OK", 2) != 2) die("Failed to write to pipe: %m");//report readiness
    struct killparams killparams;
    killparams.time = limits.time;
    killparams.pid = nsrun_pid;
    clone(killafter, killstack + STACK_SIZE, SIGCHLD, &killparams);
    if (waitpid(nsrun_pid, NULL, 0) == -1) die("Failed to wait pid %d: %m\n", nsrun_pid);
    remove_cgroup();
    return 0;
}