use rustyline::{
    Cmd, ConditionalEventHandler, DefaultEditor, Event, EventContext, EventHandler, KeyCode,
    KeyEvent, Modifiers, RepeatCount, Result,
};

struct FilteringEventHandler;
impl ConditionalEventHandler for FilteringEventHandler {
    fn handle(&self, evt: &Event, _: RepeatCount, _: bool, _: &EventContext) -> Option<Cmd> {
        if let Some(KeyEvent(KeyCode::Char(c), m)) = evt.get(0) {
            if m.contains(Modifiers::CTRL) || m.contains(Modifiers::ALT) || c.is_ascii_digit() {
                None
            } else {
                Some(Cmd::Noop) // filter out invalid input
            }
        } else {
            None
        }
    }
}

fn main() -> Result<()> {
    let mut rl = DefaultEditor::new()?;

    rl.bind_sequence(
        Event::Any,
        EventHandler::Conditional(Box::new(FilteringEventHandler)),
    );

    loop {
        let line = rl.readline("> ")?;
        println!("Num: {line}");
    }
}