From abd7f486a0fb34320e3afae6780677cfd4ff85cc Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 25 Apr 2021 19:19:28 +0100
Subject: Erring toward complete JSON loader

---
 lib/jsonParse-persistance.cpp | 11 +++----
 lib/jsonParse-persistance.h   | 13 ++++-----
 lib/persistance.cpp           | 11 +++++--
 lib/persistance.h             | 68 +++++++++++++++++++++++++++----------------
 4 files changed, 63 insertions(+), 40 deletions(-)

(limited to 'lib')

diff --git a/lib/jsonParse-persistance.cpp b/lib/jsonParse-persistance.cpp
index 89887da..ad9fc2a 100644
--- a/lib/jsonParse-persistance.cpp
+++ b/lib/jsonParse-persistance.cpp
@@ -1,11 +1,10 @@
 #include "jsonParse-persistance.h"
 
 namespace Persistanace {
-	JsonParsePersistance::JsonParsePersistance(std::istream & in) : json::jsonParser {&in} { }
-
 	void
-	JsonParsePersistance::loadState()
+	JsonParsePersistance::loadState(std::istream & in)
 	{
+		this->switch_streams(&in, nullptr);
 		yy_push_state(0);
 		yylex();
 	}
@@ -13,7 +12,8 @@ namespace Persistanace {
 	void
 	JsonParsePersistance::BeginObject()
 	{
-		stk.push(current()->BeginObject());
+		current()->beforeValue(stk);
+		current()->BeginObject(stk);
 	}
 
 	void
@@ -61,7 +61,8 @@ namespace Persistanace {
 	void
 	JsonParsePersistance::EndObject()
 	{
-		stk.pop();
+		current()->EndObject(stk);
+		current()->EndObject(stk);
 	}
 
 	template<typename T>
diff --git a/lib/jsonParse-persistance.h b/lib/jsonParse-persistance.h
index d5c76ed..bea93e0 100644
--- a/lib/jsonParse-persistance.h
+++ b/lib/jsonParse-persistance.h
@@ -11,18 +11,18 @@
 namespace Persistanace {
 	class JsonParsePersistance : public json::jsonParser {
 	public:
-		explicit JsonParsePersistance(std::istream & in);
-
 		template<typename T>
-		void
-		loadState(T & t)
+		inline T
+		loadState(std::istream & in)
 		{
+			T t {};
 			stk.push(std::make_unique<SelectionT<T>>(std::ref(t)));
-			loadState();
+			loadState(in);
+			return t;
 		}
 
 	protected:
-		void loadState();
+		void loadState(std::istream & in);
 
 		void BeginObject() override;
 		void BeginArray() override;
@@ -34,7 +34,6 @@ namespace Persistanace {
 		void EndArray() override;
 		void EndObject() override;
 
-	private:
 		Stack stk;
 
 		template<typename T> inline void PushValue(T && value);
diff --git a/lib/persistance.cpp b/lib/persistance.cpp
index 7539b44..bdcbe9f 100644
--- a/lib/persistance.cpp
+++ b/lib/persistance.cpp
@@ -47,8 +47,8 @@ namespace Persistanace {
 		throw std::runtime_error("Unexpected array");
 	}
 
-	SelectionPtr
-	Selection::BeginObject()
+	void
+	Selection::BeginObject(Stack &)
 	{
 		throw std::runtime_error("Unexpected object");
 	}
@@ -62,7 +62,12 @@ namespace Persistanace {
 	SelectionPtr
 	Selection::select(const std::string &)
 	{
-		throw std::runtime_error("Unexpected persist");
+		throw std::runtime_error("Unexpected select");
+	}
+
+	void
+	Selection::EndObject(Stack &)
+	{
 	}
 
 	static_assert(!SelectionT<float>::ArrayLike);
diff --git a/lib/persistance.h b/lib/persistance.h
index 92366f2..7f28ad1 100644
--- a/lib/persistance.h
+++ b/lib/persistance.h
@@ -32,7 +32,8 @@ namespace Persistanace {
 		virtual void operator()(const std::nullptr_t &);
 		virtual void operator()(std::string &);
 		virtual void BeginArray(Stack &);
-		virtual SelectionPtr BeginObject();
+		virtual void BeginObject(Stack &);
+		virtual void EndObject(Stack &);
 		virtual void beforeValue(Stack &);
 		virtual SelectionPtr select(const std::string &);
 	};
@@ -94,28 +95,13 @@ namespace Persistanace {
 		explicit SelectionT(std::vector<T> & value) : v {value} { }
 
 		void
-		BeginArray(Stack &) override
-		{
-		}
-
-		void
-		beforeValue(Stack & stk) override
+		BeginArray(Stack & stk) override
 		{
 			stk.push(std::make_unique<SelectionT<T>>(std::ref(v.emplace_back())));
 		}
 
-		static constexpr bool ArrayLike {true};
-		std::vector<T> & v;
-	};
-
-	template<typename T>
-	concept ArrayLike = SelectionT<T>::ArrayLike;
-
-	template<ArrayLike T> struct SelectionT<std::vector<T>> : public Selection {
-		explicit SelectionT(std::vector<T> & value) : v {value} { }
-
 		void
-		BeginArray(Stack & stk) override
+		beforeValue(Stack & stk) override
 		{
 			stk.push(std::make_unique<SelectionT<T>>(std::ref(v.emplace_back())));
 		}
@@ -172,10 +158,12 @@ namespace Persistanace {
 				}
 				else {
 					if (!v) {
-						if constexpr (!std::is_abstract_v<T>) {
+						if constexpr (std::is_abstract_v<T>) {
+							throw std::runtime_error("cannot select member of null object");
+						}
+						else {
 							v = std::make_unique<T>();
 						}
-						throw std::runtime_error("cannot select member of null object");
 					}
 					PersistanceStore ps {mbr};
 					v->persist(ps);
@@ -183,18 +171,48 @@ namespace Persistanace {
 				}
 			}
 
+			void
+			EndObject(Stack & stk) override
+			{
+				if (!v) {
+					if constexpr (std::is_abstract_v<T>) {
+						throw std::runtime_error("cannot default create abstract object");
+					}
+					else {
+						v = std::make_unique<T>();
+					}
+				}
+				stk.pop();
+			}
+
 			Ptr & v;
 		};
 
-		explicit SelectionT(std::unique_ptr<T> & o) : v {o} { }
+		explicit SelectionT(Ptr & o) : v {o} { }
+
+		void
+		beforeValue(Stack &) override
+		{
+		}
+
+		void
+		operator()(const std::nullptr_t &) override
+		{
+			v.reset();
+		}
 
-		SelectionPtr
-		BeginObject() override
+		void
+		BeginObject(Stack & stk) override
+		{
+			stk.push(std::make_unique<SelectionObj>(v));
+		}
+		void
+		EndObject(Stack & stk) override
 		{
-			return std::make_unique<SelectionObj>(v);
+			stk.pop();
 		}
 
-		std::unique_ptr<T> & v;
+		Ptr & v;
 	};
 }
 
-- 
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