lazy callback (#539)

include/cinatra/coro_http_router.hpp

@@ -1,6 +1,4 @@
 #pragma once
-#include <async_simple/coro/Lazy.h>
-
 #include <algorithm>
 #include <functional>
 #include <set>
@@ -17,17 +15,6 @@
 #include "ylt/util/type_traits.h"
 
 namespace cinatra {
-template <template <typename...> class U, typename T>
-struct is_template_instant_of : std::false_type {};
-
-template <template <typename...> class U, typename... args>
-struct is_template_instant_of<U, U<args...>> : std::true_type {};
-
-template <typename T>
-constexpr inline bool is_lazy_v =
-    is_template_instant_of<async_simple::coro::Lazy,
-                           std::remove_cvref_t<T>>::value;
-
 template <class, class = void>
 struct has_before : std::false_type {};
 
@@ -64,7 +51,7 @@ class coro_http_router {
     // hold keys to make sure map_handles_ key is
     // std::string_view, avoid memcpy when route
     using return_type = typename util::function_traits<Func>::return_type;
-    if constexpr (is_lazy_v<return_type>) {
+    if constexpr (coro_io::is_lazy_v<return_type>) {
       std::function<async_simple::coro::Lazy<void>(coro_http_request & req,
                                                    coro_http_response & resp)>
           http_handler;

include/cinatra/coro_http_server.hpp

@@ -150,7 +150,7 @@ class coro_http_server {
     static_assert(std::is_member_function_pointer_v<Func>,
                   "must be member function");
     using return_type = typename util::function_traits<Func>::return_type;
-    if constexpr (is_lazy_v<return_type>) {
+    if constexpr (coro_io::is_lazy_v<return_type>) {
       std::function<async_simple::coro::Lazy<void>(coro_http_request & req,
                                                    coro_http_response & resp)>
           f = std::bind(handler, &owner, std::placeholders::_1,

include/cinatra/ylt/coro_io/coro_io.hpp

@@ -10,6 +10,8 @@
 #include <asio/ssl.hpp>
 #endif
 
+#include <async_simple/coro/Lazy.h>
+
 #include <asio/connect.hpp>
 #include <asio/dispatch.hpp>
 #include <asio/experimental/channel.hpp>
@@ -26,6 +28,9 @@
 #include "io_context_pool.hpp"
 
 namespace coro_io {
+template <typename T>
+constexpr inline bool is_lazy_v =
+    util::is_specialization_v<std::remove_cvref_t<T>, async_simple::coro::Lazy>;
 
 template <typename Arg, typename Derived>
 class callback_awaitor_base {
@@ -380,9 +385,64 @@ async_simple::coro::Lazy<std::pair<
   });
 }
 
+template <typename T>
+inline decltype(auto) select_impl(T &pair) {
+  using Func = std::tuple_element_t<1, std::remove_cvref_t<T>>;
+  using ValueType =
+      typename std::tuple_element_t<0, std::remove_cvref_t<T>>::ValueType;
+  using return_type = std::invoke_result_t<Func, async_simple::Try<ValueType>>;
+
+  auto &callback = std::get<1>(pair);
+  if constexpr (coro_io::is_lazy_v<return_type>) {
+    auto executor = std::get<0>(pair).getExecutor();
+    return std::make_pair(
+        std::move(std::get<0>(pair)),
+        [executor, callback = std::move(callback)](auto &&val) {
+          if (executor) {
+            callback(std::move(val)).via(executor).start([](auto &&) {
+            });
+          }
+          else {
+            callback(std::move(val)).start([](auto &&) {
+            });
+          }
+        });
+  }
+  else {
+    return pair;
+  }
+}
+
 template <typename... T>
-auto select(T &&...args) {
-  return async_simple::coro::collectAny(std::forward<T>(args)...);
+inline auto select(T &&...args) {
+  return async_simple::coro::collectAny(select_impl(args)...);
+}
+
+template <typename T, typename Callback>
+inline auto select(std::vector<T> vec, Callback callback) {
+  if constexpr (coro_io::is_lazy_v<Callback>) {
+    std::vector<async_simple::Executor *> executors;
+    for (auto &lazy : vec) {
+      executors.push_back(lazy.getExecutor());
+    }
+
+    return async_simple::coro::collectAny(
+        std::move(vec),
+        [executors, callback = std::move(callback)](size_t index, auto &&val) {
+          auto executor = executors[index];
+          if (executor) {
+            callback(index, std::move(val)).via(executor).start([](auto &&) {
+            });
+          }
+          else {
+            callback(index, std::move(val)).start([](auto &&) {
+            });
+          }
+        });
+  }
+  else {
+    return async_simple::coro::collectAny(std::move(vec), std::move(callback));
+  }
 }
 
 template <typename Socket, typename AsioBuffer>