feat: add vec3 type to nhollman json / fix: scene serialisation stuff

destrum/src/Graphics/Resources/PrimitiveMeshes.cpp

@@ -1,7 +1,9 @@
 #include <destrum/Graphics/Resources/PrimitiveMeshes.h>
 
 #include <array>
+#include <charconv>
 #include <cstdint>
+#include <format>
 
 CPUMesh PrimitiveMeshes::MakeBox(const glm::vec3& size)
 {
@@ -22,7 +24,8 @@ CPUMesh PrimitiveMeshes::MakeBox(const glm::vec3& size)
     }};
 
     CPUMesh mesh{};
-    mesh.name = "Box";
+    // The name becomes the mesh cache key, saved scenes rebuild the box from it
+    mesh.name = BoxKey(size);
     mesh.minPos = -size * 0.5f;
     mesh.maxPos = size * 0.5f;
 
@@ -50,3 +53,65 @@ CPUMesh PrimitiveMeshes::MakeBox(const glm::vec3& size)
 
     return mesh;
 }
+
+namespace {
+    constexpr std::string_view PrimitiveScheme = "prim://";
+    constexpr std::string_view BoxPrefix = "prim://box?size=";
+}
+
+std::string PrimitiveMeshes::BoxKey(const glm::vec3& size)
+{
+    return std::format("{}{},{},{}", BoxPrefix, size.x, size.y, size.z);
+}
+
+bool PrimitiveMeshes::IsPrimitiveKey(std::string_view key)
+{
+    return key.starts_with(PrimitiveScheme);
+}
+
+std::string_view PrimitiveMeshes::StripDuplicateSuffix(std::string_view key)
+{
+    // MeshCache appends "#N" when the same key is added more than once
+    const auto separator = key.rfind('#');
+    if (separator == std::string_view::npos || separator + 1 >= key.size()) {
+        return key;
+    }
+    for (const char c : key.substr(separator + 1)) {
+        if (c < '0' || c > '9') {
+            return key;
+        }
+    }
+    return key.substr(0, separator);
+}
+
+std::optional<CPUMesh> PrimitiveMeshes::MakeFromKey(std::string_view key)
+{
+    key = StripDuplicateSuffix(key);
+    if (!key.starts_with(BoxPrefix)) {
+        return std::nullopt;
+    }
+
+    std::string_view rest = key.substr(BoxPrefix.size());
+    glm::vec3 size{0.0f};
+    for (int i = 0; i < 3; ++i) {
+        const char* end = rest.data() + rest.size();
+        float value = 0.0f;
+        const auto [next, error] = std::from_chars(rest.data(), end, value);
+        if (error != std::errc{} || !(value > 0.0f)) {
+            return std::nullopt;
+        }
+        size[i] = value;
+        rest.remove_prefix(static_cast<std::size_t>(next - rest.data()));
+        if (i < 2) {
+            if (!rest.starts_with(',')) {
+                return std::nullopt;
+            }
+            rest.remove_prefix(1);
+        }
+    }
+    if (!rest.empty()) {
+        return std::nullopt;
+    }
+
+    return MakeBox(size);
+}