#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void usage (void);

bool
is_util (char *str)
{
  char *utils[] = { "./bin/cat",  "./bin/chmod", "./bin/cut",   "./bin/env",
                    "./bin/head", "./bin/ls",    "./bin/repeat" };

  for (size_t i = 0; i < 7; i++)
    {
      if (strcmp (str, utils[i]) == 0)
        {
          return true;
        }
    }

  return false;
}

int
main (int argc, char *argv[], char *envp[])
{
  size_t envp_count = 0;
  while (envp[envp_count] != NULL) envp_count++;

  size_t env_args = 0;
  char* util = NULL;

  for (size_t i = 1; i < argc; i++)
    {
      if (is_util (argv[i])) {
        util = argv[i];
        break;
      }

      env_args++;
    }

  if (util == NULL) {
    usage();
    exit(EXIT_FAILURE);
  }

  char **combined_envp = calloc (envp_count + env_args + 1, sizeof (char *));
  memcpy (combined_envp, envp, envp_count * sizeof (char *));
  memcpy (combined_envp + envp_count, &argv[1], env_args * sizeof (char *));
  combined_envp[envp_count + env_args] = NULL;

  execve(util, &argv[env_args + 1], combined_envp);

  return EXIT_SUCCESS;
}

static void
usage (void)
{
  printf ("env, set environment variables and execute program\n");
  printf ("usage: env [name=value ...] PROG ARGS\n");
}