lines.rs

struct LineIterator<'a> {
    iter: std::iter::Peekable<std::str::SplitWhitespace<'a>>,
    width: usize,
}

impl<'a> LineIterator<'a> {
    fn new(width: usize, text: &str) -> LineIterator {
        LineIterator {
            iter: text.split_whitespace().peekable(),
            width: width,
        }
    }
}

impl<'a> std::iter::Iterator for LineIterator<'a> {
    type Item = String;

    fn next(&mut self) -> Option<String> {
        let mut line = vec![];
        let mut length = 0;
        loop {
            match self.iter.peek() {
                Some(word) => {
                    if length == 0 || self.width > length + word.len() {
                        line.push(word.to_string());
                        length += word.len() + 1;
                    } else {
                        break;
                    }
                }
                None => {
                    if length == 0 {
                        return None;
                    } else {
                        break;
                    }
                }
            }
            self.iter.next();
        }
        Some(line.join(" "))
    }
}

fn chunk_text(width: usize, text: &str) -> Vec<String> {
    LineIterator::new(width, text).collect()
}