#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"

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);
}

//const size_t STACK_SIZE=1000000;
#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;
}

static void prepare_userns(int pid) {
    char path[100];
    char line[100];

    int uid = 0;
    int gid = 0;
    int unprivileged_uid=66534;
    int unprivileged_gid=65534;

    sprintf(path, "/proc/%d/uid_map", pid);
    sprintf(line, "0 %d 1\n1 %d 1000\n", uid, unprivileged_uid);
    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);
    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");
    //getting binary folder
    char bin_path[PATH_MAX];
    if (realpath (argv[0], bin_path) == 0) die("unable to resolve real path: %m"); 
    for(int i = strlen(bin_path);i>0 && bin_path[i]!='/';i--) bin_path[i]=0;
    if(chdir(bin_path)) die("unable to chdir to binary path: %m");
    //setting random seed
    srand(time(NULL));
    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");
    int clone_flags = SIGCHLD | CLONE_NEWUTS | CLONE_NEWUSER | CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWCGROUP/* | CLONE_NEWTIME*/;
    int nsrun_pid=clone(nsrun,nmstack+STACK_SIZE,clone_flags,&params);
    int pipe=params.fd[1];
    //sleep(1);
    prepare_userns(nsrun_pid);
    if (nsrun_pid<0) {die("faled to clone");}
    add_to_cgroup(nsrun_pid);
    //dup2(STDOUT_FILENO,params.out[0]);
    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;
}