#[allow(unused)] // for the doc comments
use std::any::Any;
#[allow(unused)] // for the doc comments
use std::fmt::Debug;

#[allow(unused)] // for the doc comments
use dyn_clone::DynClone;

#[allow(unused)] // for the doc comments
use crate::foreign::{Atomic, ExternFn};
#[allow(unused)] // for the doc comments
use crate::representations::Primitive;

/// A macro that generates implementations of [Atomic] to simplify the
/// development of external bindings for Orchid.
///
/// The macro depends on implementations of [AsRef<Clause>] and [From<(&Self,
/// Clause)>] for extracting the clause to be processed and then reconstructing
/// the [Atomic]. Naturally, supertraits of [Atomic] are also dependencies.
/// These are [Any], [Debug] and [DynClone].
///
/// The simplest form just requires the typename to be specified. This
/// additionally depends on an implementation of [ExternFn] because after the
/// clause is fully normalized it returns `Self` wrapped in a
/// [Primitive::ExternFn]. It is intended for intermediary stages of the
/// function where validation and the next state are defined in
/// [ExternFn::apply].
///
/// ```
/// atomic_impl!(Multiply1)
/// ```
///
/// The last stage of the function should use the extended form of the macro
/// which takes an additional closure to explicitly describe what happens when
/// the argument is fully processed.
///
/// ```
/// // excerpt from the exact implementation of Multiply
/// atomic_impl!(Multiply0, |Self(a, cls): &Self| {
///   let b: Numeric = cls.clone().try_into().map_err(AssertionError::into_extern)?;
///   Ok(*a * b).into())
/// })
/// ```
#[macro_export]
macro_rules! atomic_impl {
  ($typ:ident) => {
    atomic_impl! {$typ, |this: &Self, _: $crate::interpreter::Context| {
      use $crate::foreign::ExternFn;
      Ok(this.clone().to_xfn_cls())
    }}
  };
  ($typ:ident, $next_phase:expr) => {
    impl $crate::foreign::Atomic for $typ {
      $crate::atomic_defaults! {}

      fn run(
        &self,
        ctx: $crate::interpreter::Context,
      ) -> $crate::foreign::AtomicResult {
        // extract the expression
        let expr =
          <Self as AsRef<$crate::foreign::RcExpr>>::as_ref(self).clone();
        // run the expression
        let ret = $crate::interpreter::run(expr, ctx.clone())?;
        let $crate::interpreter::Return { gas, state, inert } = ret;
        // rebuild the atomic
        let next_self =
          <Self as From<(&Self, $crate::foreign::RcExpr)>>::from((self, state));
        // branch off or wrap up
        let clause = if inert {
          let closure = $next_phase;
          match closure(&next_self, ctx) {
            Ok(r) => r,
            Err(e) => return Err($crate::interpreter::RuntimeError::Extern(e)),
          }
        } else {
          next_self.to_atom_cls()
        };
        // package and return
        Ok($crate::foreign::AtomicReturn { clause, gas, inert: false })
      }
    }
  };
}