1 files changed, 60 insertions, 0 deletions
diff --git a/entity/erased-constraints.hpp b/entity/erased-constraints.hpp
new file mode 100644
index 00000000..4f1262f1
--- /dev/null
+++ b/entity/erased-constraints.hpp
@@ -0,0 +1,60 @@
+#pragma once
+#include <cstddef>
+#include <limits>
+
+namespace floormat::entities::erased_constraints {
+
+static_assert(sizeof(std::size_t) == sizeof(std::uintptr_t));
+static_assert(sizeof(std::size_t) == sizeof(std::ptrdiff_t));
+
+struct range final
+{
+    using U = std::size_t;
+    using I = std::make_signed_t<U>;
+    enum type_ : unsigned char { type_none, type_float, type_uint, type_int, };
+    union element {
+        float f;
+        U u;
+        I i;
+    };
+
+    element min {.i = 0}, max {.i = 0};
+    type_ type = type_none;
+
+    template<typename T> constexpr std::pair<T, T> convert() const;
+};
+
+template<typename T> constexpr std::pair<T, T> range::convert() const
+{
+    if constexpr (!std::is_floating_point_v<T> && !std::is_integral_v<T>)
+        return {{}, {}};
+
+    using std::size_t;
+    static_assert(sizeof(T) <= sizeof(size_t) || !std::is_integral_v<T>);
+
+    constexpr auto min_ = []<typename V>(V a, V b) { return a < b ? a : b; };
+    constexpr auto max_ = []<typename V>(V a, V b) { return a > b ? a : b; };
+    using limits = std::numeric_limits<T>;
+    constexpr auto lmin = limits::min(), lmax = limits::max();
+
+    switch (type) {
+    case type_float:
+        if constexpr (limits::is_integer())
+            return { T(std::floor(min.f)), T(std::ceil(max.f)) };
+        else
+            return { T(min.f), T(max.f) };
+    case type_uint:  return { max_(T(min.u), lmin), T(min_(size_t(max.u), size_t(lmax))) };
+    case type_int:   return { max_(T(min.i), lmin), T(min_(size_t(max.i), size_t(lmax))) };
+    default: case type_none:  return { lmin, lmax };
+    }
+}
+
+struct length final {
+    std::size_t value = std::numeric_limits<std::size_t>::max();
+};
+
+struct group final {
+    StringView group_name;
+};
+
+} // namespace floormat::entities::erased_constraints