From 01538457a54cc188f1cfa3f70993cc498cc6cb1d Mon Sep 17 00:00:00 2001
From: Slendi <slendi@socopon.com>
Date: Wed, 11 Mar 2026 23:26:37 +0200
Subject: [PATCH] Add interop API

Signed-off-by: Slendi <slendi@socopon.com>
---
 include/smath.hpp |  17 ++++++++
 tests/interop.cpp | 101 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 tests/interop.cpp

diff --git a/include/smath.hpp b/include/smath.hpp
index 5bda624..46e2899 100644
--- a/include/smath.hpp
+++ b/include/smath.hpp
@@ -1186,6 +1186,23 @@ template<typename T>
 	return m;
 }
 
+
+template<class Ext> struct interop_adapter;
+
+template<class Ext>
+constexpr auto from_external(Ext const &ext)
+    -> typename interop_adapter<Ext>::smath_type
+{
+	return interop_adapter<Ext>::to_smath(ext);
+}
+
+template<class Ext, class SMathT>
+constexpr auto to_external(SMathT const &value) -> Ext
+{
+	return interop_adapter<Ext>::from_smath(value);
+}
+
+
 } // namespace smath
 
 template<std::size_t N, typename T>
diff --git a/tests/interop.cpp b/tests/interop.cpp
new file mode 100644
index 0000000..30f9d13
--- /dev/null
+++ b/tests/interop.cpp
@@ -0,0 +1,101 @@
+#include <type_traits>
+
+#include <gtest/gtest.h>
+
+#include <smath.hpp>
+
+struct ExternalVec3f {
+	float x;
+	float y;
+	float z;
+};
+
+struct ExternalMat2f {
+	float m00;
+	float m01;
+	float m10;
+	float m11;
+};
+
+namespace smath {
+
+template<> struct interop_adapter<ExternalVec3f> {
+	using smath_type = Vec<3, float>;
+
+	static constexpr auto to_smath(ExternalVec3f const &v) -> smath_type
+	{
+		return { v.x, v.y, v.z };
+	}
+
+	static constexpr auto from_smath(smath_type const &v) -> ExternalVec3f
+	{
+		return { v[0], v[1], v[2] };
+	}
+};
+
+template<> struct interop_adapter<ExternalMat2f> {
+	using smath_type = Mat<2, 2, float>;
+
+	static constexpr auto to_smath(ExternalMat2f const &m) -> smath_type
+	{
+		smath_type out {};
+		out(0, 0) = m.m00;
+		out(0, 1) = m.m01;
+		out(1, 0) = m.m10;
+		out(1, 1) = m.m11;
+		return out;
+	}
+
+	static constexpr auto from_smath(smath_type const &m) -> ExternalMat2f
+	{
+		return { m(0, 0), m(0, 1), m(1, 0), m(1, 1) };
+	}
+};
+
+} // namespace smath
+
+TEST(Interop, FromExternalVec) {
+	ExternalVec3f ext { 1.0f, 2.0f, 3.0f };
+	auto v = smath::from_external(ext);
+
+	static_assert(std::is_same_v<decltype(v), smath::Vec<3, float>>);
+	EXPECT_EQ(v[0], 1.0f);
+	EXPECT_EQ(v[1], 2.0f);
+	EXPECT_EQ(v[2], 3.0f);
+}
+
+TEST(Interop, ToExternalVec) {
+	smath::Vec3 v { 4.0f, 5.0f, 6.0f };
+	auto ext = smath::to_external<ExternalVec3f>(v);
+
+	EXPECT_EQ(ext.x, 4.0f);
+	EXPECT_EQ(ext.y, 5.0f);
+	EXPECT_EQ(ext.z, 6.0f);
+}
+
+TEST(Interop, RoundtripVec) {
+	ExternalVec3f ext { 7.0f, 8.0f, 9.0f };
+	auto v = smath::from_external(ext);
+	auto ext2 = smath::to_external<ExternalVec3f>(v);
+
+	EXPECT_EQ(ext2.x, 7.0f);
+	EXPECT_EQ(ext2.y, 8.0f);
+	EXPECT_EQ(ext2.z, 9.0f);
+}
+
+TEST(Interop, MatrixConversion) {
+	ExternalMat2f ext { 1.0f, 2.0f, 3.0f, 4.0f };
+	auto m = smath::from_external(ext);
+
+	static_assert(std::is_same_v<decltype(m), smath::Mat<2, 2, float>>);
+	EXPECT_EQ(m(0, 0), 1.0f);
+	EXPECT_EQ(m(0, 1), 2.0f);
+	EXPECT_EQ(m(1, 0), 3.0f);
+	EXPECT_EQ(m(1, 1), 4.0f);
+
+	auto ext2 = smath::to_external<ExternalMat2f>(m);
+	EXPECT_EQ(ext2.m00, 1.0f);
+	EXPECT_EQ(ext2.m01, 2.0f);
+	EXPECT_EQ(ext2.m10, 3.0f);
+	EXPECT_EQ(ext2.m11, 4.0f);
+}