internal
void print_help(const char *argv0)
{
  fprintf(stderr,
    "rntviewer v" V_MAJOR "." V_MINOR " by silverweed"
    "\n"
    "\nUsage: %s [-t] [-s START] [-l LEN] [-w WIDTH] <ntuple_name> <ntuple_file.root>"   
    "\n\t-t: no graphics, output to terminal"
    "\n\t-s: set first displayed byte to START"
    "\n\t-l: display LEN bytes (only in terminal mode)"
    "\n\t-w: display WIDTH bytes per column"
    "\n"
  , argv0);
}

struct Cmdline_Args {
  b8 print_to_terminal;
  b8 show_help_and_exit;
  u64 start_addr;
  u64 nbytes_displayed;
  u16 n_cols;

  String8 ntpl_name;
  String8 file_name;
};

struct Conv_Res {
  u64 num;
  b8 error;
};

internal
Conv_Res str_to_u64(String8 s)
{
  Conv_Res res {};
  if (s.size > 2 && s[0] == '0' && s[1] == 'x') {
    // hexadecimal
    for (u64 i = 2; i < s.size; ++i) {
      u8 c = s.str[i];
      if (c >= '0' && c <= '9') {
        res.num *= 16;
        res.num += c - '0';
      } else if (c >= 'A' && c <= 'F') {
        res.num *= 16;
        res.num += 10 + c - 'A';
      } else if (c >= 'a' && c <= 'f') {
        res.num *= 16;
        res.num += 10 + c - 'a';
      } else {
        res.error = true;
        break;
      }
    }
  } else {
    // decimal
    for (u64 i = 0; i < s.size; ++i) {
      u8 c = s.str[i];
      if (c >= '0' && c <= '9') {
        res.num *= 10;
        res.num += c - '0';
      } else {
        res.error = true;
        break;
      }
    }
  }
  return res;
}

internal
void parse_int_arg(i32 &cur_arg_idx, i32 argc, char **argv, u64 &out)
{
  const char *arg = argv[cur_arg_idx];
  if (cur_arg_idx < argc - 1) {
    String8 nxt_arg = str8_from_c(argv[++cur_arg_idx]);
    Conv_Res res = str_to_u64(nxt_arg);
    if (res.error)
      fprintf(stderr, "Invalid integer after %s flag.\n", arg);
    else
      out = res.num;
  } else {
    fprintf(stderr, "Argument required after %s flag.\n", arg);
  }
}

internal
Cmdline_Args parse_args(i32 argc, char **argv)
{
  Cmdline_Args args {};
  if (argc < 3) {
    args.show_help_and_exit = true;
    return args;
  }

// TODO: refactor this probably
  for (i32 i = 1; i < argc; ++i) {
    String8 arg = str8_from_c(argv[i]);
    if (arg.str[0] == '-') {
      if (arg.size == 2) {
        if (arg.str[1] == 't')
          args.print_to_terminal = true;
        else if (arg.str[1] == 's')
          parse_int_arg(i, argc, argv, args.start_addr);
        else if (arg.str[1] == 'l')
          parse_int_arg(i, argc, argv, args.nbytes_displayed);
        else if (arg.str[1] == 'w') {
          u64 n_cols = 0;
          parse_int_arg(i, argc, argv, n_cols);
          args.n_cols = (u16)n_cols;
        }
        else
          args.show_help_and_exit = true;   
      } else {
        args.show_help_and_exit = true;   
      }
    } else if (args.ntpl_name.size) {
      if (args.file_name.size)
        args.show_help_and_exit = true;
      else
        args.file_name = arg;
    } else {
      args.ntpl_name = arg;
    }
  }
  return args;
}