// Taken from: https://github.com/rust-lang/regex/issues/330#issuecomment-274058261
use regex::{CaptureMatches, Captures, Regex};

pub struct SplitCaptures<'r, 't> {
  finder: CaptureMatches<'r, 't>,
  text: &'t str,
  last: usize,
  caps: Option<Captures<'t>>,
}

impl<'r, 't> SplitCaptures<'r, 't> {
  pub fn new(re: &'r Regex, text: &'t str) -> SplitCaptures<'r, 't> {
    SplitCaptures {
      finder: re.captures_iter(text),
      text,
      last: 0,
      caps: None,
    }
  }
}

#[derive(Debug)]
pub enum SplitState<'t> {
  Unmatched(&'t str),
  Captured(Captures<'t>),
}

impl<'r, 't> Iterator for SplitCaptures<'r, 't> {
  type Item = SplitState<'t>;

  fn next(&mut self) -> Option<SplitState<'t>> {
    if let Some(caps) = self.caps.take() {
      return Some(SplitState::Captured(caps));
    }
    match self.finder.next() {
      None => {
        if self.last >= self.text.len() {
          None
        } else {
          let s = &self.text[self.last..];
          self.last = self.text.len();
          Some(SplitState::Unmatched(s))
        }
      }
      Some(caps) => {
        let m = caps.get(0).unwrap();
        let unmatched = &self.text[self.last..m.start()];
        self.last = m.end();
        self.caps = Some(caps);
        Some(SplitState::Unmatched(unmatched))
      }
    }
  }
}