use crate::*;

/// Event source
pub trait Input: Sized {
    /// Type of input event
    type Event;
    /// Result of handling input
    type Handled; // TODO: make this an Option<Box dyn Command<Self>> containing the undo
    /// Currently handled event
    fn event (&self) -> &Self::Event;
    /// Whether component should exit
    fn is_done (&self) -> bool;
    /// Mark component as done
    fn done (&self);
}

flex_trait_mut!(Handle <E: Input> {
    fn handle (&mut self, _input: &E) -> Perhaps<E::Handled> {
        Ok(None)
    }
});

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)
    }
}