1 files changed, 173 insertions, 0 deletions
diff --git a/engine/src/reflection.rs b/engine/src/reflection.rs
new file mode 100644
index 0000000..83bc636
--- /dev/null
+++ b/engine/src/reflection.rs
@@ -0,0 +1,173 @@
+use std::alloc::Layout;
+use std::any::{TypeId, type_name};
+use std::fmt::Debug;
+
+pub use engine_macros::Reflection;
+
+/// Trait implemented by types that support runtime reflection on them.
+///
+/// # Safety
+/// Implementors of this trait must provide accurate reflection information in the
+/// `TYPE_REFLECTION` associated constant and the `type_reflection` and
+/// `get_type_reflection` methods.
+pub unsafe trait Reflection: 'static
+{
+    const TYPE_REFLECTION: &Type;
+
+    fn type_reflection() -> &'static Type
+    where
+        Self: Sized,
+    {
+        Self::TYPE_REFLECTION
+    }
+
+    fn get_type_reflection(&self) -> &'static Type
+    {
+        Self::TYPE_REFLECTION
+    }
+}
+
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum Type
+{
+    Struct(Struct),
+    Array(Array),
+    Slice(Slice),
+    Literal(Literal),
+}
+
+impl Type
+{
+    pub const fn as_struct(&self) -> Option<&Struct>
+    {
+        match self {
+            Self::Struct(struct_reflection) => Some(struct_reflection),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Struct
+{
+    pub fields: &'static [StructField],
+}
+
+#[derive(Debug, Clone)]
+pub struct StructField
+{
+    pub name: &'static str,
+    pub index: usize,
+    pub layout: Layout,
+    pub byte_offset: usize,
+    pub type_id: TypeId,
+    pub type_name: &'static str,
+    pub get_type: FnWithDebug<Option<&'static Type>>,
+}
+
+impl StructField
+{
+    pub fn type_reflection(&self) -> Option<&'static Type>
+    {
+        self.get_type.get()
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Array
+{
+    pub item_reflection: &'static Type,
+    pub length: usize,
+}
+
+#[derive(Debug, Clone)]
+pub struct Slice
+{
+    pub item_reflection: &'static Type,
+}
+
+#[derive(Debug)]
+pub struct Literal
+{
+    pub layout: Layout,
+    pub type_id: TypeId,
+    pub type_name: fn() -> &'static str,
+}
+
+macro_rules! impl_with_for_literals {
+    ($($literal: ty),*) => {
+        $(
+            unsafe impl Reflection for $literal
+            {
+                const TYPE_REFLECTION: &Type = &Type::Literal(Literal {
+                    layout: Layout::new::<$literal>(),
+                    type_id: TypeId::of::<$literal>(),
+                    type_name: || type_name::<$literal>()
+                });
+            }
+        )*
+    };
+}
+
+impl_with_for_literals!(
+    u8,
+    i8,
+    u16,
+    i16,
+    u32,
+    i32,
+    u64,
+    i64,
+    u128,
+    i128,
+    f32,
+    f64,
+    usize,
+    isize,
+    &'static str
+);
+
+unsafe impl<T: Reflection, const LEN: usize> Reflection for [T; LEN]
+{
+    const TYPE_REFLECTION: &Type = &Type::Array(Array {
+        item_reflection: T::TYPE_REFLECTION,
+        length: LEN,
+    });
+}
+
+unsafe impl<T: Reflection> Reflection for &'static [T]
+{
+    const TYPE_REFLECTION: &Type =
+        &Type::Slice(Slice { item_reflection: T::TYPE_REFLECTION });
+}
+
+#[derive(Clone)]
+pub struct FnWithDebug<Value>
+{
+    func: fn() -> Value,
+}
+
+impl<Value> FnWithDebug<Value>
+{
+    pub const fn new(func: fn() -> Value) -> Self
+    {
+        Self { func }
+    }
+
+    pub fn get(&self) -> Value
+    {
+        (self.func)()
+    }
+}
+
+impl<Value: Debug> Debug for FnWithDebug<Value>
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        formatter
+            .debug_tuple("FnWithDebug")
+            .field(&self.get())
+            .finish()
+    }
+}