fn to_acronym(word: &str) -> Option<String> {
    if word.chars().all(|c| c.is_uppercase() || !c.is_alphabetic())
        || word.chars().all(|c| c.is_lowercase() || !c.is_alphabetic())
    {
        word.chars()
            .find(|c| c.is_alphabetic())
            .map(|c| c.to_uppercase().to_string())
    } else {
        Some(word.chars().filter(|c| c.is_uppercase()).collect())
    }
}

pub fn abbreviate(phrase: &str) -> String {
    phrase
        .split(|c| " -:,".contains(c)) // Split into words
        .filter(|s| !s.is_empty())
        .flat_map(to_acronym)
        .collect()
}