use crate::*;

macro_rules!dsl_sym(
    (|$state:ident:$State:ty| -> $type:ty {$($lit:literal => $exp:expr),* $(,)?})=>{
        impl<'t> DslSymNs<'t, $type> for $State {
            const NS: DslNs<'t, fn (&'t $State)->$type> =
                DslNs(&[$(($lit, |$state: &$State|$exp)),*]); } });

pub trait DslSymNs<'t, T: 't>: 't {
    const NS: DslNs<'t, fn (&'t Self)->T>;
}

pub struct DslNs<'t, T: 't>(pub &'t [(&'t str, T)]);

pub type DslCb = fn (&App) -> Box<dyn Render<TuiOut>>;

impl<'t, D: Dsl> std::ops::Index<D> for DslNs<'t, DslCb> {
    type Output = DslCb;
    fn index (&self, index: D) -> &Self::Output {
        if let Ok(Some(symbol)) = index.src() {
            for (key, value) in self.0.iter() {
                if symbol == *key {
                    return value
                }
            }
        }
        &(view_nil as DslCb)
    }
}
fn view_nil (_: &App) -> Box<dyn Render<TuiOut>> {
    Box::new(Fill::xy("·"))
}