cli-matcher.rs

enum DispatchResult<'a, T> {
    Matched(&'a T),
    Ambiguous(Vec<&'a String>),
    NotFound,
}

fn dispatch<'a, T>(command: &str, candidates: &'a Vec<(String, T)>) -> DispatchResult<'a, T> {
    let matches = candidates.iter()
        .filter(|c| c.0.starts_with(command))
        .collect::<Vec<_>>();
    if matches.len() == 1 {
        DispatchResult::Matched(&matches[0].1)
    } else if matches.len() == 0 {
        DispatchResult::NotFound
    } else {
        DispatchResult::Ambiguous(matches.iter().map(|c| &c.0).collect::<Vec<_>>())
    }
}

fn main() {
    let commands: Vec<(String, Box<dyn Fn()>)> = vec![
        (String::from("start"),  Box::new(|| start_work())),
        (String::from("status"), Box::new(|| show_status())),
    ];
    match env::args().nth(1) {
        Some(command) => match dispatch(&command, &commands) {
            DispatchResult::Matched(target) => target(),
            DispatchResult::Ambiguous(matches) => {
                println!("More than one command matches prefix '{}':", command);
                for m in matches {
                    println!("\t{}", m);
                }
                println!("Please be more specific");
            },
            DispatchResult::NotFound => usage(),
        }
        None => usage(),
    }
}