use crate::*;
/// Implement `EdnProvide` for a type and context
#[macro_export] macro_rules! edn_provide {
    ($lt:lifetime: $type:ty:|$self:ident:$State:ty|{ $($pat:pat => $expr:expr),* $(,)? }) => {
        impl<$lt> EdnProvide<$lt, $type> for $State {
            fn get <S: AsRef<str>> (&$lt $self, edn: &$lt EdnItem<S>) -> Option<$type> {
                Some(match edn.to_ref() { $(EdnItem::Sym($pat) => $expr,)* _ => return None })
            }
        }
    };
    ($type:ty:|$self:ident:$State:ty|{ $($pat:pat => $expr:expr),* $(,)? }) => {
        impl<'a> EdnProvide<'a, $type> for $State {
            fn get <S: AsRef<str>> (&'a $self, edn: &'a EdnItem<S>) -> Option<$type> {
                Some(match edn.to_ref() { $(EdnItem::Sym($pat) => $expr,)* _ => return None })
            }
        }
    };
}
/// Map EDN tokens to parameters of a given type for a given context
pub trait EdnProvide<'a, U>: Sized {
    fn get <S: AsRef<str>> (&'a self, _edn: &'a EdnItem<S>) -> Option<U> {
        None
    }
    fn get_or_fail <S: AsRef<str>> (&'a self, edn: &'a EdnItem<S>) -> U {
        self.get(edn).expect("no value")
    }
}
impl<'a, T: EdnProvide<'a, U>, U> EdnProvide<'a, U> for &T {
    fn get <S: AsRef<str>> (&'a self, edn: &'a EdnItem<S>) -> Option<U> {
        (*self).get(edn)
    }
    fn get_or_fail <S: AsRef<str>> (&'a self, edn: &'a EdnItem<S>) -> U {
        (*self).get_or_fail(edn)
    }
}
impl<'a, T: EdnProvide<'a, U>, U> EdnProvide<'a, U> for Option<T> {
    fn get <S: AsRef<str>> (&'a self, edn: &'a EdnItem<S>) -> Option<U> {
        self.as_ref().map(|s|s.get(edn)).flatten()
    }
    fn get_or_fail <S: AsRef<str>> (&'a self, edn: &'a EdnItem<S>) -> U {
        self.as_ref().map(|s|s.get_or_fail(edn)).expect("no provider")
    }
}