#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <spawn.h>
#include <shmem.h>

extern char **environ;

int main(int argc, char *argv[])
{
  if (argc == 1)
  {
    printf("Hello, from the child process\n");
    return 0;
  }

  shmem_init();

  const int spawn_mode = atoi(argv[1]);
  char * spawn_prog = argv[argc >= 3 ? 2 : 0];

  int rc, errnum;
  pid_t pid = 0;
  char *child_argv[2] = { spawn_prog, NULL };
  switch (spawn_mode)
  {
  case 1:
  case 2:
    errno = 0;
    pid = (spawn_mode == 1 ? fork() : vfork());
    errnum = errno;
    if (pid == -1)
    {
      fprintf(stderr, "ERROR: %s returned -1 (%d: %s)\n",
              (spawn_mode == 1 ? "fork()" : "vfork()"),
              errnum, strerror(errnum));
      exit(1);
    }
    else if (pid == 0)
    {
      errno = 0;
      rc = execvp(spawn_prog, child_argv);
      errnum = errno;
      if (rc == -1)
      {
        fprintf(stderr, "ERROR: execvp returned -1 (%d: %s)\n",
                errnum, strerror(errnum));
        _Exit(1); // _Exit is needed for vfork()
      }
    }
    break;
  case 3:
    rc = posix_spawn(&pid, spawn_prog, NULL, NULL, child_argv, environ);
    if (rc != 0)
    {
      fprintf(stderr, "ERROR: posix_spawn returned non-zero (%d: %s)\n",
              rc, strerror(rc));
      exit(1);
    }
    break;
  default:
    fprintf(stderr, "ERROR: invalid spawn mode\n");
    exit(1);
  }

  int status;
  waitpid(pid, &status, 0);
  if (WIFEXITED(status))
  {
    rc = WEXITSTATUS(status);
    printf("%d/%d: child exited with status %d\n",
           rc, shmem_my_pe(), shmem_n_pes());
  }
  else if (WIFSIGNALED(status))
  {
    rc = WTERMSIG(status);
    printf("%d/%d: child terminated by signal %d\n",
           rc, shmem_my_pe(), shmem_n_pes());
  }

  shmem_finalize();

  return 0;
}