1 files changed, 78 insertions, 0 deletions
diff --git a/entity/constraints.hpp b/entity/constraints.hpp
new file mode 100644
index 00000000..21d549c5
--- /dev/null
+++ b/entity/constraints.hpp
@@ -0,0 +1,78 @@
+#pragma once
+#include <cmath>
+#include <type_traits>
+#include <utility>
+#include <algorithm>
+#include <Corrade/Containers/StringView.h>
+
+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
+{
+    using limits = std::numeric_limits<T>;
+    switch (type) {
+    case type_float:
+        if constexpr (limits::is_integer())
+            return { T(std::floor(min.f)), T(std::ceil(max.f)) };
+        else
+            return { min.f, max.f };
+    case type_uint:  return { std::max(T(min.u), limits::min()), std::min(T(max.u), limits::max()) };
+    case type_int:   return { std::max(T(min.i), limits::min()), std::min(T(max.i), limits::max()) };
+    default: case type_none:  return { limits::min(), limits::max() };
+    }
+}
+
+struct length final {
+    std::size_t value = (std::size_t)-1;
+};
+
+struct group final {
+    StringView group_name;
+};
+
+} // namespace floormat::entities::erased_constraints
+
+namespace floormat::entities::constraints {
+
+template<typename T> struct range {
+    using limits = std::numeric_limits<T>;
+    T min = limits::min(), max = limits::max();
+
+    constexpr operator erased_constraints::range() const;
+};
+
+template<typename T> constexpr range<T>::operator erased_constraints::range() const
+{
+    using enum erased_constraints::range::type_;
+    if constexpr (std::is_floating_point_v<T>)
+        return { { .f = min }, { .f = max }, type_float };
+    if constexpr (std::is_integral_v<T> && std::is_unsigned_v<T>)
+        return { {.u = min}, {.u = max}, type_uint };
+    if constexpr (std::is_integral_v<T> && std::is_signed_v<T>)
+        return { {.i = min}, {.i = max}, type_int };
+    return { {}, {}, type_none };
+}
+
+using length = erased_constraints::length;
+using group = erased_constraints::group;
+
+} // namespace floormat::entities::constraints