use std::any::TypeId;
use any::Any;
use engine::{Engine, EvalAltResult};
pub trait RegisterFn<FN, ARGS, RET> {
fn register_fn(&mut self, name: &str, f: FN);
}
pub struct Ref<A>(A);
pub struct Mut<A>(A);
macro_rules! count_args {
() => {0usize};
($head:ident $($tail:ident)*) => {1usize + count_args!($($tail)*)};
}
macro_rules! def_register {
() => {
def_register!(imp);
};
(imp $($par:ident => $mark:ty => $param:ty => $clone:expr),*) => {
impl<$($par,)* FN, RET> RegisterFn<FN, ($($mark,)*), RET> for Engine
where
$($par: Any + Clone,)*
FN: Fn($($param),*) -> RET + 'static,
RET: Any,
{
fn register_fn(&mut self, name: &str, f: FN) {
let fun = move |mut args: Vec<&mut Any>| {
if args.len() != count_args!($($par)*) {
return Err(EvalAltResult::ErrorFunctionArgMismatch);
}
let mut drain = args.drain(..);
$(
let $par = ((*drain.next().unwrap()).downcast_mut() as Option<&mut $par>)
.ok_or(EvalAltResult::ErrorFunctionArgMismatch)?;
)*
Ok(Box::new(f($(($clone)($par)),*)) as Box<Any>)
};
self.register_fn_raw(name.to_owned(), Some(vec![$(TypeId::of::<$par>()),*]), Box::new(fun));
}
}
};
($p0:ident $(, $p:ident)*) => {
def_register!(imp $p0 => $p0 => $p0 => Clone::clone $(, $p => $p => $p => Clone::clone)*);
def_register!(imp $p0 => Ref<$p0> => &$p0 => |x| { x } $(, $p => $p => $p => Clone::clone)*);
def_register!(imp $p0 => Mut<$p0> => &mut $p0 => |x| { x } $(, $p => $p => $p => Clone::clone)*);
def_register!($($p),*);
};
}
#[cfg_attr(rustfmt, rustfmt_skip)]
def_register!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);