pub fn convert(word: impl AsRef<str>) -> String {
    let word = word.as_ref();

    let mut first_consonant = None;

    let prefix: String = word.chars().enumerate().filter_map(|(i, c)|{
        if i == 0 && !"aeiou".contains(c) {
            first_consonant = Some(c);
            None
        } else {
            Some(c)
        }
    }).collect();

    format!("{}-{}ay", prefix, first_consonant.unwrap_or('h'))
}

fn main() {
    println!("{}  {}", convert("apple"), convert("banana"));
}