use super::{Env, FromValue, NativeFunction, Value};

macro_rules! impl_function {
    ( $($ty:ident),* $(,)? ) => {
        #[allow(non_snake_case, unused_variables, unused_mut, unused_assignments)]
        impl<F,R,$($ty,)*> NativeFunction<($($ty,)*)> for F
        where
            F: Fn($(&$ty,)*) -> R,
            R: Into<Value>,
            $($ty: FromValue,)*
        {
            fn native_execute(&self, _: &Env, args: &[Value]) -> Result<Value, String> {
                let mut args = args.iter();
                let total_count = {
                    let mut count = 0;
                    $(
                        let _: Option<$ty> = None;
                        count += 1;
                    )*
                    count
                };
                let mut count = 0;
                $(
                    let arg = args.next()
                    .ok_or_else(|| format!("method expected {} parameters, but parameter {} was missing", total_count, count))?;
                    let $ty = $ty::from_value(arg)
                    .ok_or_else(|| format!("Parameter {} was not of type {}, it was {}", count, std::any::type_name::<$ty>(), arg.value_kind()))?;
                    count += 1;
                )*
                Ok(self($($ty,)*).into())
            }
        }


        #[allow(non_snake_case, unused_variables, unused_mut, unused_assignments)]
        impl<F,R,$($ty,)*> NativeFunction<((), $($ty,)*)> for F
        where
            F: Fn(&Env, $(&$ty,)*) -> R,
            R: Into<Value>,
            $($ty: FromValue,)*
        {
            fn native_execute(&self, env: &Env, args: &[Value]) -> Result<Value, String> {
                let mut args = args.iter();
                let total_count = {
                    let mut count = 0;
                    $(
                        let _: Option<$ty> = None;
                        count += 1;
                    )*
                    count
                };
                let mut count = 0;
                $(
                    let arg = args.next()
                    .ok_or_else(|| format!("method expected {} parameters, but parameter {} was missing", total_count, count))?;
                    let $ty = $ty::from_value(arg)
                    .ok_or_else(|| format!("Parameter {} was not of type {}, it was {}", count, std::any::type_name::<$ty>(), arg.value_kind()))?;
                    count += 1;
                )*
                Ok(self(env, $($ty,)*).into())
            }
        }

    };
}

crate::macros::for_each_tuple!(impl_function);