From 07c8ed0cf9472186dc178955083e3e7d0109d659 Mon Sep 17 00:00:00 2001
From: Denis Blank <denis.blank@outlook.com>
Date: Sun, 25 Nov 2018 02:54:35 +0100
Subject: [PATCH] Add invoker for the result class and specialized ones

---
 include/continuable/continuable-result.hpp |  9 +++
 include/continuable/detail/core/base.hpp   | 74 ++++++++++++++++++----
 2 files changed, 71 insertions(+), 12 deletions(-)

diff --git a/include/continuable/continuable-result.hpp b/include/continuable/continuable-result.hpp
index 4441a3d..bd48cbe 100644
--- a/include/continuable/continuable-result.hpp
+++ b/include/continuable/continuable-result.hpp
@@ -182,6 +182,15 @@ public:
   }
 };
 
+template <typename T>
+struct is_result : std::false_type {};
+template <typename... T>
+struct is_result<result<T...>> : std::true_type {};
+template <>
+struct is_result<empty_result> : std::true_type {};
+template <>
+struct is_result<exceptional_result> : std::true_type {};
+
 template <typename... T>
 constexpr auto make_result(T&&... values) {
   return result<detail::traits::unrefcv_t<T>...>(std::forward<T>(values)...);
diff --git a/include/continuable/detail/core/base.hpp b/include/continuable/detail/core/base.hpp
index 2f93595..faf83a0 100644
--- a/include/continuable/detail/core/base.hpp
+++ b/include/continuable/detail/core/base.hpp
@@ -159,9 +159,9 @@ constexpr auto make_invoker(T&& invoke, hints::signature_hint_tag<Args...>) {
 }
 
 /// - continuable<?...> -> result(next_callback);
-template <typename Data, typename Annotation>
+template <typename Hint, typename Data, typename Annotation>
 constexpr auto
-invoker_of(traits::identity<continuable_base<Data, Annotation>>) {
+invoker_of(Hint, traits::identity<continuable_base<Data, Annotation>>) {
   /// Get the hint of the unwrapped returned continuable
   using Type =
       decltype(std::declval<continuable_base<Data, Annotation>>().finish());
@@ -184,8 +184,8 @@ invoker_of(traits::identity<continuable_base<Data, Annotation>>) {
 }
 
 /// - ? -> next_callback(?)
-template <typename T>
-constexpr auto invoker_of(traits::identity<T>) {
+template <typename Hint, typename T>
+constexpr auto invoker_of(Hint, traits::identity<T>) {
   return make_invoker(
       [](auto&& callback, auto&& next_callback, auto&&... args) {
         CONTINUABLE_BLOCK_TRY_BEGIN
@@ -201,7 +201,8 @@ constexpr auto invoker_of(traits::identity<T>) {
 }
 
 /// - void -> next_callback()
-inline auto invoker_of(traits::identity<void>) {
+template <typename Hint>
+auto invoker_of(Hint, traits::identity<void>) {
   return make_invoker(
       [](auto&& callback, auto&& next_callback, auto&&... args) {
         CONTINUABLE_BLOCK_TRY_BEGIN
@@ -214,6 +215,51 @@ inline auto invoker_of(traits::identity<void>) {
       traits::identity<>{});
 }
 
+/// - empty_result -> <cancel>
+template <typename Hint>
+auto invoker_of(Hint, traits::identity<empty_result>) {
+  return make_invoker(
+      [](auto&& callback, auto&& next_callback, auto&&... args) {
+        /*CONTINUABLE_BLOCK_TRY_BEGIN
+          util::partial_invoke(std::forward<decltype(callback)>(callback),
+                               std::forward<decltype(args)>(args)...);
+          invoke_no_except(
+              std::forward<decltype(next_callback)>(next_callback));
+        CONTINUABLE_BLOCK_TRY_END*/
+      },
+      Hint{});
+}
+
+/// - exceptional_result -> Hint
+template <typename Hint>
+auto invoker_of(Hint, traits::identity<exceptional_result>) {
+  return make_invoker(
+      [](auto&& callback, auto&& next_callback, auto&&... args) {
+        /*CONTINUABLE_BLOCK_TRY_BEGIN
+        util::partial_invoke(std::forward<decltype(callback)>(callback),
+        std::forward<decltype(args)>(args)...);
+        invoke_no_except(
+        std::forward<decltype(next_callback)>(next_callback));
+        CONTINUABLE_BLOCK_TRY_END*/
+      },
+      Hint{});
+}
+
+/// - result<Args...> -> Args...
+template <typename Hint, typename... Args>
+auto invoker_of(Hint, traits::identity<result<Args...>>) {
+  return make_invoker(
+      [](auto&& callback, auto&& next_callback, auto&&... args) {
+        /*CONTINUABLE_BLOCK_TRY_BEGIN
+        util::partial_invoke(std::forward<decltype(callback)>(callback),
+        std::forward<decltype(args)>(args)...);
+        invoke_no_except(
+        std::forward<decltype(next_callback)>(next_callback));
+        CONTINUABLE_BLOCK_TRY_END*/
+      },
+      traits::identity<Args...>{});
+}
+
 /// Returns a sequenced invoker which is able to invoke
 /// objects where std::get is applicable.
 inline auto sequenced_unpack_invoker() {
@@ -240,15 +286,15 @@ inline auto sequenced_unpack_invoker() {
 } // namespace decoration
 
 // - std::pair<?, ?> -> next_callback(?, ?)
-template <typename First, typename Second>
-constexpr auto invoker_of(traits::identity<std::pair<First, Second>>) {
+template <typename Hint, typename First, typename Second>
+constexpr auto invoker_of(Hint, traits::identity<std::pair<First, Second>>) {
   return make_invoker(sequenced_unpack_invoker(),
                       traits::identity<First, Second>{});
 }
 
 // - std::tuple<?...>  -> next_callback(?...)
-template <typename... Args>
-constexpr auto invoker_of(traits::identity<std::tuple<Args...>>) {
+template <typename Hint, typename... Args>
+constexpr auto invoker_of(Hint, traits::identity<std::tuple<Args...>>) {
   return make_invoker(sequenced_unpack_invoker(), traits::identity<Args...>{});
 }
 
@@ -327,7 +373,9 @@ struct result_handler_base<handle_results::yes, Base,
         std::move(static_cast<Base*>(this)->callback_), std::move(args)...))>{};
 
     // Pick the correct invoker that handles decorating of the result
-    auto invoker = decoration::invoker_of(result);
+    auto invoker =
+        decoration::invoker_of(hints::signature_hint_tag<Args...>{}, //
+                               result);
 
     // Invoke the callback
     packed_dispatch(std::move(static_cast<Base*>(this)->executor_),
@@ -493,13 +541,15 @@ template <typename T, typename... Args>
 constexpr auto
 next_hint_of(std::integral_constant<handle_results, handle_results::yes>,
              traits::identity<T> /*callback*/,
-             hints::signature_hint_tag<Args...> /*current*/) {
+             hints::signature_hint_tag<Args...> current) {
   // Partial Invoke the given callback
   using Result = decltype(
       util::partial_invoke(std::declval<T>(), std::declval<Args>()...));
 
   // Return the hint of thr given invoker
-  return decltype(decoration::invoker_of(traits::identify<Result>{}).hint()){};
+  return decltype(decoration::invoker_of(current, //
+                                         traits::identify<Result>{})
+                      .hint()){};
 }
 /// Don't progress the hint when we don't continue
 template <typename T, typename... Args>