use std::path::MAIN_SEPARATOR;
use path_parsing::{last_sep_i, last_non_sep_i, last_non_sep_i_before};

pub fn dirname(path: &str) -> String {
  let r_str = path;
  if r_str.is_empty() {
    return ".".to_string();
  }
  let non_sep_i = last_non_sep_i(r_str);
  if non_sep_i == -1 {
    return MAIN_SEPARATOR.to_string();
  }
  let sep_i = last_sep_i(r_str, non_sep_i);
  if sep_i == -1 {
    return ".".to_string();
  }
  if sep_i == 0 {
    return MAIN_SEPARATOR.to_string();
  }
  let non_sep_i2 = last_non_sep_i_before(r_str, sep_i);
  if non_sep_i2 != -1 {
    return r_str[..(non_sep_i2 + 1) as usize].to_string();
  } else {
    return MAIN_SEPARATOR.to_string();
  }
}

#[test]
fn returns_dot_for_empty_string(){
  assert_eq!(dirname(""), ".".to_string());
}