From b59ba638083122456bfeab0ff1fc7e3f3af99423 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 23 Feb 2023 00:39:06 +0000
Subject: Support parsing string values in persistence read

---
 lib/persistence.h            | 47 +++++++++++++++++++++++++++++++++++++++++---
 test/fixtures/json/conv.json |  4 ++++
 test/test-persistence.cpp    |  8 ++++++++
 3 files changed, 56 insertions(+), 3 deletions(-)
 create mode 100644 test/fixtures/json/conv.json

diff --git a/lib/persistence.h b/lib/persistence.h
index 0fc0200..bfd27f0 100644
--- a/lib/persistence.h
+++ b/lib/persistence.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <charconv>
 #include <functional>
 #include <glm/glm.hpp>
 #include <iosfwd>
@@ -87,13 +88,53 @@ namespace Persistence {
 		T & v;
 	};
 
-	template<typename T> struct SelectionT : public SelectionV<T> {
+	template<typename T>
+	concept Scalar = std::is_scalar_v<T>;
+	template<typename T>
+	concept NotScalar = (!Scalar<T>);
+
+	template<Scalar T> struct SelectionT<T> : public SelectionV<T> {
+		using SelectionV<T>::SelectionV;
+		using Selection::setValue;
+
+		void
+		setValue(T evalue) override
+		{
+			std::swap(this->v, evalue);
+		}
+
+		void
+		setValue(std::string && evalue) override
+		{
+			if constexpr (std::same_as<T, bool>) {
+				using namespace std::literals;
+				if (!(this->v = evalue == "true"sv)) {
+					if (evalue != "false"sv) {
+						throw std::runtime_error("Value conversion failure");
+					}
+				}
+			}
+			else {
+				if (auto res = std::from_chars(evalue.c_str(), evalue.c_str() + evalue.length(), this->v).ec;
+						res != std::errc {}) {
+					throw std::runtime_error("Value conversion failure");
+				}
+			}
+		}
+
+		void
+		write(const Writer & out) const override
+		{
+			out.pushValue(this->v);
+		}
+	};
+
+	template<NotScalar T> struct SelectionT<T> : public SelectionV<T> {
 		using SelectionV<T>::SelectionV;
 		using Selection::setValue;
-		using P = std::conditional_t<std::is_scalar_v<T>, T, T &&>;
 
 		void
-		setValue(P evalue) override
+		setValue(T && evalue) override
 		{
 			std::swap(this->v, evalue);
 		}
diff --git a/test/fixtures/json/conv.json b/test/fixtures/json/conv.json
new file mode 100644
index 0000000..1b690d5
--- /dev/null
+++ b/test/fixtures/json/conv.json
@@ -0,0 +1,4 @@
+{
+	"bl": "true",
+	"flt": "3.14"
+}
diff --git a/test/test-persistence.cpp b/test/test-persistence.cpp
index faa0d19..6bee010 100644
--- a/test/test-persistence.cpp
+++ b/test/test-persistence.cpp
@@ -208,6 +208,14 @@ BOOST_FIXTURE_TEST_CASE(load_vector_ptr, JPP)
 	BOOST_CHECK(to->vptr.at(3)->str.empty());
 }
 
+BOOST_FIXTURE_TEST_CASE(test_conversion, JPP)
+{
+	auto to = load_json<std::unique_ptr<TestObject>>(FIXTURESDIR "json/conv.json");
+	BOOST_REQUIRE(to);
+	BOOST_CHECK_EQUAL(to->bl, true);
+	BOOST_CHECK_EQUAL(to->flt, 3.14F);
+}
+
 struct SharedTestObject : public Persistence::Persistable {
 	SharedTestObject() = default;
 
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