use crate::*;

pub trait Command<S>: Send + Sync + Sized {
    fn execute (self, state: &mut S) -> Perhaps<Self>;
    fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
        where Self: Sized
    {
        Ok(self.execute(state)?.map(wrap))
    }
}

impl<S, T: Command<S>> Command<S> for Option<T> {
    fn execute (self, _: &mut S) -> Perhaps<Self> {
        Ok(None)
    }
    fn delegate <U> (self, _: &mut S, _: impl Fn(Self)->U) -> Perhaps<U>
        where Self: Sized
    {
        Ok(None)
    }
}