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Telegram/lib_rpl/rpl/after_next.h

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+// This file is part of Desktop App Toolkit,
+// a set of libraries for developing nice desktop applications.
+//
+// For license and copyright information please follow this link:
+// https://github.com/desktop-app/legal/blob/master/LEGAL
+//
+#pragma once
+
+#include <rpl/producer.h>
+
+namespace rpl {
+namespace details {
+
+template <typename SideEffect>
+class after_next_helper {
+public:
+	template <typename OtherSideEffect>
+	after_next_helper(OtherSideEffect &&method)
+		: _method(std::forward<OtherSideEffect>(method)) {
+	}
+
+	template <typename Value, typename Error, typename Generator>
+	auto operator()(producer<Value, Error, Generator> &&initial) {
+		return make_producer<Value, Error>([
+			initial = std::move(initial),
+			method = std::move(_method)
+		](const auto &consumer) mutable {
+			return std::move(initial).start(
+			[method = std::move(method), consumer](auto &&value) {
+				auto copy = method;
+				consumer.put_next_copy(value);
+				details::callable_invoke(
+					std::move(copy),
+					std::forward<decltype(value)>(value));
+			}, [consumer](auto &&error) {
+				consumer.put_error_forward(
+					std::forward<decltype(error)>(error));
+			}, [consumer] {
+				consumer.put_done();
+			});
+		});
+	}
+
+private:
+	SideEffect _method;
+
+};
+
+} // namespace details
+
+template <typename SideEffect>
+inline auto after_next(SideEffect &&method)
+-> details::after_next_helper<std::decay_t<SideEffect>> {
+	return details::after_next_helper<std::decay_t<SideEffect>>(
+		std::forward<SideEffect>(method));
+}
+
+} // namespace rpl