From 1da06cc4d8b64b8d63782e356acb0cb946789d20 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Wed, 25 Oct 2023 17:12:45 +0200
Subject: codec: Added basic interface and function class

Preparation work for RPC functionality.
---
 c++/codec/rpc.h | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/codec.cpp | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 211 insertions(+)
 create mode 100644 c++/codec/rpc.h

diff --git a/c++/codec/rpc.h b/c++/codec/rpc.h
new file mode 100644
index 0000000..b1422a9
--- /dev/null
+++ b/c++/codec/rpc.h
@@ -0,0 +1,103 @@
+#pragma once
+
+#include <forstio/core/error.h>
+#include "schema.h"
+#include "data.h"
+
+namespace saw {
+template<typename SchemaFunc, typename Encode, typename Func>
+class function;
+
+template<typename Request, typename Response, typename Encode, typename Func>
+class function<schema::Function<Request, Response>, Encode, Func> {
+private:
+		Func func_;
+public:
+		function(Func func):
+				func_{std::move(func)}
+		{}
+
+		error_or<data<Response, Encode>> call(data<Request, Encode> req){
+				return func_(std::move(req));
+		}
+};
+
+template<typename T, typename Encode, typename... Funcs>
+class interface;
+
+template<typename... Requests, typename... Responses, string_literal... Names, typename Encode, typename... Funcs>
+class interface<schema::Interface<schema::Member<schema::Function<Requests, Responses>, Names>...>, Encode, Funcs...> {
+private:
+		std::tuple<function<schema::Function<Requests, Responses>, Encode, Funcs>...> funcs_;
+public:
+		interface(function<schema::Function<Requests, Responses>, Encode, Funcs>... funcs):
+				funcs_{std::move(funcs)...}
+		{}
+
+		/**
+		 * Get the function based on the string literal matching the position in the tuple
+		 */
+		template<string_literal Lit>
+		function<
+				schema::Function<
+						typename parameter_pack_type<
+								parameter_key_pack_index<
+										Lit, Names...
+								>::value
+						, Requests...>::type
+				,
+						typename parameter_pack_type<
+								parameter_key_pack_index<
+										Lit, Names...
+								>::value
+						, Responses...>::type
+				>
+		,
+				Encode
+		,
+				typename parameter_pack_type<
+						parameter_key_pack_index<
+								Lit, Names...
+						>::value
+				, Funcs...>::type
+		>& get(){
+				return std::get<parameter_key_pack_index<Lit, Names...>::value>(funcs_);
+		}
+
+		template<string_literal Lit>
+		error_or<data<
+				typename parameter_pack_type<
+						parameter_key_pack_index<
+								Lit, Names...
+						>::value
+				, Responses...>::type
+		, Encode>> call(
+						data<
+								typename parameter_pack_type<
+										parameter_key_pack_index<
+												Lit, Names...
+										>::value
+								, Requests...>::type
+						, Encode> req
+				){
+				return get<Lit>().call(std::move(req));
+		}
+
+};
+
+template<typename T, typename Encode>
+struct function_factory {
+		template<typename Func>
+		static function<T,Encode, Func> create(Func func){
+				return function<T,Encode,Func>{std::move(func)};
+		}
+};
+
+template<typename T, typename Encode>
+struct interface_factory {
+		template<typename... Func>
+		static interface<T,Encode, Func...> create(Func... func){
+				return interface<T,Encode, Func...>{std::move(func)...};
+		}
+};
+}
diff --git a/tests/codec.cpp b/tests/codec.cpp
index 7253ecc..439332a 100644
--- a/tests/codec.cpp
+++ b/tests/codec.cpp
@@ -1,6 +1,7 @@
 #include <forstio/test/suite.h>
 #include <forstio/codec/data.h>
 #include <forstio/codec/simple.h>
+#include <forstio/codec/rpc.h>
 
 #include <iostream>
 
@@ -27,6 +28,19 @@ using TestTuple = Tuple<
 	TwoDimArray,
 	UInt64
 >;
+
+using TestInt32Pair = Tuple<
+	Int32,
+	Int32
+>;
+
+using TestCalcFunction = Function<TestInt32Pair, Int32>;
+
+using TestInterface = Interface<
+	Member<TestCalcFunction, "add">,
+	Member<TestCalcFunction, "sub">,
+	Member<TestCalcFunction, "multiply">
+>;
 }
 SAW_TEST("One Dimensional Array") {
 	using namespace saw;
@@ -256,6 +270,7 @@ SAW_TEST("KelSimple Tuple write and read back"){
 	SAW_EXPECT(dec_tda.at(0,1).get() == 3, "Incorrect Decoding in array 0,1");
 	SAW_EXPECT(native.template get<1>().get() == 410, "Incorrect Decoding in number");
 }
+
 SAW_TEST("KelSimple String write and read back"){
 	using namespace saw;
 
@@ -279,4 +294,97 @@ SAW_TEST("KelSimple String write and read back"){
 
 	SAW_EXPECT(native == str, "String should've been decoded back correctly");
 }
+
+SAW_TEST("Function basics"){
+	using namespace saw;
+
+	{
+			data<schema::TestInt32Pair, encode::Native> native;
+
+			native.get<0>().set(5);
+			native.get<1>().set(40);
+
+			auto func_add = function_factory<schema::TestCalcFunction, encode::Native>::create(
+				[](data<schema::TestInt32Pair, encode::Native> req){
+						data<schema::Int32, encode::Native> resp;
+
+						resp.set(req.get<0>().get() + req.get<1>().get());
+
+						return resp;
+				}
+			);
+
+			auto eov = func_add.call(std::move(native));
+			SAW_EXPECT(eov.is_value(), "Returned value is an error");
+
+			auto& val = eov.get_value();
+			SAW_EXPECT(val.get() == 45, "Sum is incorrect");
+	}
+}
+
+SAW_TEST("Interface basics"){
+	using namespace saw;
+
+	data<schema::TestInt32Pair, encode::Native> native;
+
+	auto func_add = 
+		[](data<schema::TestInt32Pair, encode::Native> req){
+				data<schema::Int32, encode::Native> resp;
+
+				resp.set(req.get<0>().get() + req.get<1>().get());
+
+				return resp;
+		};
+	auto func_sub = 
+		[](data<schema::TestInt32Pair, encode::Native> req){
+				data<schema::Int32, encode::Native> resp;
+
+				resp.set(req.get<0>().get() - req.get<1>().get());
+
+				return resp;
+		};
+	auto func_multiply = [](data<schema::TestInt32Pair, encode::Native> req){
+				data<schema::Int32, encode::Native> resp;
+
+				resp.set(req.get<0>().get() * req.get<1>().get());
+
+				return resp;
+		};
+
+	auto iface = interface_factory<schema::TestInterface, encode::Native>::create(std::move(func_add), std::move(func_sub), std::move(func_multiply));
+
+    {
+			data<schema::TestInt32Pair, encode::Native> native;
+
+			native.get<0>().set(5);
+			native.get<1>().set(40);
+			auto eov = iface.template call<"add">(std::move(native));
+			SAW_EXPECT(eov.is_value(), "Returned value is an error");
+
+			auto& val = eov.get_value();
+			SAW_EXPECT(val.get() == 45, "Sum is incorrect");
+	}
+    {
+			data<schema::TestInt32Pair, encode::Native> native;
+
+			native.get<0>().set(5);
+			native.get<1>().set(40);
+			auto eov = iface.template call<"sub">(std::move(native));
+			SAW_EXPECT(eov.is_value(), "Returned value is an error");
+
+			auto& val = eov.get_value();
+			SAW_EXPECT(val.get() == -35, "Sum is incorrect");
+	}
+    {
+			data<schema::TestInt32Pair, encode::Native> native;
+
+			native.get<0>().set(5);
+			native.get<1>().set(40);
+			auto eov = iface.template call<"multiply">(std::move(native));
+			SAW_EXPECT(eov.is_value(), "Returned value is an error");
+
+			auto& val = eov.get_value();
+			SAW_EXPECT(val.get() == 200, "Sum is incorrect");
+	}
+}
 }
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