From e2b2f8b9a395a235e26e4b449b3498a2c0410f8f Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Thu, 29 Jun 2023 10:48:32 +0200
Subject: c++,codec-json: Added Struct decoding

---
 src/codec-json/json.tmpl.h | 99 +++++++++++++++++++++++++++++++++++++++++++++-
 tests/codec-json.cpp       |  5 +--
 2 files changed, 100 insertions(+), 4 deletions(-)

diff --git a/src/codec-json/json.tmpl.h b/src/codec-json/json.tmpl.h
index 8fb01a9..6cf7189 100644
--- a/src/codec-json/json.tmpl.h
+++ b/src/codec-json/json.tmpl.h
@@ -461,9 +461,106 @@ struct json_decode<schema::String, RootSchema, ToDecode> {
 
 template<typename... T, string_literal... Lits, typename RootSchema, typename ToDecode>
 struct json_decode<schema::Struct<schema::Member<T,Lits>...>, RootSchema, ToDecode> {
+	template<std::size_t i>
+	static error_or<void> decode_field_search(buffer_view& buff, data<schema::Struct<schema::Member<T,Lits>...>, ToDecode>& to, std::array<bool, sizeof...(T)>& fields, const data<schema::String,ToDecode>& search_name){
+		if constexpr ( i < sizeof...(T)){
+			using Type = typename parameter_pack_type<i, T...>::type;
+			constexpr static string_literal Literal = parameter_key_pack_type<i, Lits...>::literal;
+			if(search_name == Literal.view()){
+				if(fields[i]){
+					// TODO Change to this
+					// return make_error<err::already_exists>();
+					return make_error<err::invalid_state>();
+				}
+				fields[i] = true;
+				auto eov = json_decode<Type, RootSchema, ToDecode>::decode(buff, to.template get<Literal>());
+				if(eov.is_error()){
+					return eov;
+				}
+			}else {
+				decode_field_search<i+1>(buff, to, fields, search_name);
+			}
+		}else {
+			return make_error<err::invalid_state>();
+		}
+		return void_t{};
+	}
+
+	static error_or<void> decode_fields(buffer_view& buff, data<schema::Struct<schema::Member<T,Lits>...>, ToDecode>& to, std::array<bool, sizeof...(T)>& fields){
+		for(;;){
+			data<schema::String, ToDecode> name;
+			auto eov = json_decode<schema::String, RootSchema, ToDecode>::decode(buff, name);
+			if(eov.is_error()){
+				return eov;
+			}
+			json_helper::skip_whitespace(buff);
+			if(buff.read_composite_length() == 0){
+				return make_error<err::buffer_exhausted>();
+			}
+			if(buff.read() != ':'){
+				return make_error<err::invalid_state>();
+			}
+			buff.read_advance(1);
+			json_helper::skip_whitespace(buff);
+			if(buff.read_composite_length() == 0){
+				return make_error<err::buffer_exhausted>();
+			}
+			{
+				auto eov = decode_field_search<0>(buff, to, fields, name);
+				if(eov.is_error()){
+					return eov;
+				}
+			}
+			json_helper::skip_whitespace(buff);
+			if(buff.read_composite_length() == 0){
+				return make_error<err::buffer_exhausted>();
+			}
+			if(buff.read() == ','){
+				buff.read_advance(1);
+			}else if(buff.read() == '}'){
+				// If not all fields are set, the dataset is incomplete
+				for(auto& iter : fields){
+					if(!iter){
+						return make_error<err::invalid_state>();
+					}
+				}
+				buff.read_advance(1);
+				return void_t{};
+			}else{
+				return make_error<err::invalid_state>();
+			}
+			json_helper::skip_whitespace(buff);
+			if(buff.read_composite_length() == 0){
+				return make_error<err::buffer_exhausted>();
+			}
+		}
+		return void_t{};
+	}
+
 	static error_or<void> decode(buffer_view& buff, data<schema::Struct<schema::Member<T,Lits>...>, ToDecode>& to){
+		std::array<bool, sizeof...(T)> found_fields;
+		std::fill(found_fields.begin(), found_fields.end(), false);
+
+		assert(buff.read() == '{');
+		buff.read_advance(1);
+		json_helper::skip_whitespace(buff);
+		if(buff.read_composite_length() == 0){
+			return make_error<err::buffer_exhausted>();
+		}
+		if(buff.read() == '}'){
+			if(sizeof...(T) > 0){
+				return make_error<err::invalid_state>();
+			}
+			buff.read_advance(1);
+			return void_t{};
+		}
 
-		return make_error<err::not_implemented>();
+		auto eov = decode_fields(buff, to, found_fields);
+		if(eov.is_error()){
+			return eov;
+		}
+
+		return void_t{};
 	}
 };
 
diff --git a/tests/codec-json.cpp b/tests/codec-json.cpp
index 5b4700f..926f550 100644
--- a/tests/codec-json.cpp
+++ b/tests/codec-json.cpp
@@ -285,7 +285,7 @@ SAW_TEST("Three Dim Array write and read"){
 
 }
 
-SAW_TEST("Struct write"){
+SAW_TEST("Struct read and write"){
 	using namespace saw;
 	data<schema::TestStruct, encode::Native> native;
 	data<schema::TestStruct, encode::Json> json;
@@ -302,13 +302,12 @@ SAW_TEST("Struct write"){
 	std::string enc_val = convert_to_string(json.get_buffer());
 
 	SAW_EXPECT(enc_val == str_v, std::string{"Struct not encoded correctly. Encoded: "} + enc_val + std::string{" Expected: "} + std::string{str_v});
-/*
+
 	native = {};
 	eov = json_codec.decode(json, native);
 	SAW_EXPECT(eov.is_value(), "Decoding error");
 	SAW_EXPECT(native.get<"foo">().get() == 5, "Invalid value for foo");
 	SAW_EXPECT(native.get<"bar">() == "baz", "Invalid value for bar");
-*/
 }
 
 SAW_TEST("Int8 read"){
-- 
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