feat(engine): add default value retrieval to type reflectionHEADmaster

5 files changed, 133 insertions, 4 deletions

diff --git a/engine-macros/src/reflection.rs b/engine-macros/src/reflection.rs
index 825094b..5d40e0c 100644
--- a/engine-macros/src/reflection.rs
+++ b/engine-macros/src/reflection.rs
@@ -1,3 +1,4 @@
+mod default_value;
 mod enum_impl;
 mod field;
 mod struct_impl;
diff --git a/engine-macros/src/reflection/default_value.rs b/engine-macros/src/reflection/default_value.rs
new file mode 100644
index 0000000..567c3b1
--- /dev/null
+++ b/engine-macros/src/reflection/default_value.rs
@@ -0,0 +1,42 @@
+use quote::quote;
+
+pub fn gen_get_default_value_fn(
+    type_ident: &proc_macro2::Ident,
+    type_generics: &syn::TypeGenerics,
+) -> proc_macro2::TokenStream
+{
+    quote! {
+        struct SpecializationTarget<T>(std::marker::PhantomData<T>);
+
+        trait HasDefaultValue
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>;
+        }
+
+        trait NoDefaultValue
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>;
+        }
+
+        impl<T> NoDefaultValue for &SpecializationTarget<T>
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>
+            {
+                None
+            }
+        }
+
+        impl<T> HasDefaultValue for SpecializationTarget<T>
+        where
+            T: std::default::Default + 'static
+        {
+            fn default_value_fn(&self) -> Option<fn() -> Box<dyn std::any::Any>>
+            {
+                Some(|| Box::new(T::default()))
+            }
+        }
+
+        (&SpecializationTarget::<#type_ident #type_generics>(std::marker::PhantomData))
+            .default_value_fn()
+    }
+}
diff --git a/engine-macros/src/reflection/enum_impl.rs b/engine-macros/src/reflection/enum_impl.rs
index 14142bf..611da6d 100644
--- a/engine-macros/src/reflection/enum_impl.rs
+++ b/engine-macros/src/reflection/enum_impl.rs
@@ -1,5 +1,6 @@
 use quote::{format_ident, quote, ToTokens};
 
+use crate::reflection::default_value::gen_get_default_value_fn;
 use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
 use crate::util::{find_engine_crate_path, syn_path, SynPathExt};
 
@@ -238,6 +239,8 @@ pub fn generate(input: syn::ItemEnum) -> proc_macro2::TokenStream
         }
     };
 
+    let get_default_value_fn = gen_get_default_value_fn(&input_ident, &type_generics);
+
     quote! {
         #[doc(hidden)]
         mod #mod_name {
@@ -254,7 +257,10 @@ pub fn generate(input: syn::ItemEnum) -> proc_macro2::TokenStream
                             variants: &[#(#variants),*],
                             is_unit_only: #is_unit_only,
                             discriminant_layout: #discriminant_layout,
-                            fields_layout: #fields_layout
+                            fields_layout: #fields_layout,
+                            get_default_value: || {
+                                #get_default_value_fn
+                            }
                         }
                     )
                 };
diff --git a/engine-macros/src/reflection/struct_impl.rs b/engine-macros/src/reflection/struct_impl.rs
index b1adea5..ce1086b 100644
--- a/engine-macros/src/reflection/struct_impl.rs
+++ b/engine-macros/src/reflection/struct_impl.rs
@@ -1,5 +1,6 @@
 use quote::quote;
 
+use crate::reflection::default_value::gen_get_default_value_fn;
 use crate::reflection::field::{generate as generate_field, ReflectionFieldGenOptions};
 use crate::util::{find_engine_crate_path, syn_path, SynPathExt};
 
@@ -49,6 +50,8 @@ pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
             )
         });
 
+    let get_default_value_fn = gen_get_default_value_fn(&input_ident, &type_generics);
+
     quote! {
         unsafe impl #impl_generics #engine_crate_path::reflection::Reflection for
             #input_ident #type_generics #where_clause
@@ -59,7 +62,10 @@ pub fn generate(input: syn::ItemStruct) -> proc_macro2::TokenStream
                         #engine_crate_path::reflection::Struct {
                             fields: &[
                                 #(#fields),*
-                            ]
+                            ],
+                            get_default_value: || {
+                                #get_default_value_fn
+                            }
                         }
                     )
                 };
diff --git a/engine-reflection/src/lib.rs b/engine-reflection/src/lib.rs
index c8b0004..4e5e8d8 100644
--- a/engine-reflection/src/lib.rs
+++ b/engine-reflection/src/lib.rs
@@ -1,5 +1,5 @@
 use std::alloc::Layout;
-use std::any::{type_name, TypeId};
+use std::any::{type_name, Any, TypeId};
 use std::borrow::Cow;
 use std::fmt::Debug;
 
@@ -64,12 +64,50 @@ impl Type
             _ => None,
         }
     }
+
+    #[inline]
+    pub fn default_value(&self) -> Option<Box<dyn Any>>
+    {
+        match self {
+            Self::Struct(struct_type) => struct_type.default_value(),
+            Self::Enum(enum_type) => enum_type.default_value(),
+            Self::Literal(literal_type) => literal_type.default_value(),
+            Self::Array(_) | Self::Slice(_) => None,
+        }
+    }
+
+    #[inline]
+    pub fn has_default_value(&self) -> bool
+    {
+        match self {
+            Self::Struct(struct_type) => struct_type.has_default_value(),
+            Self::Enum(enum_type) => enum_type.has_default_value(),
+            Self::Literal(literal_type) => literal_type.has_default_value(),
+            Self::Array(_) | Self::Slice(_) => false,
+        }
+    }
 }
 
 #[derive(Debug, Clone)]
 pub struct Struct
 {
     pub fields: &'static [Field],
+    pub get_default_value: fn() -> Option<DefaultValueFn>,
+}
+
+impl Struct
+{
+    #[inline]
+    pub fn default_value(&self) -> Option<Box<dyn Any>>
+    {
+        Some((self.get_default_value)()?())
+    }
+
+    #[inline]
+    pub fn has_default_value(&self) -> bool
+    {
+        (self.get_default_value)().is_some()
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -83,6 +121,23 @@ pub struct Enum
 
     pub discriminant_layout: Layout,
     pub fields_layout: Option<Layout>,
+
+    pub get_default_value: fn() -> Option<DefaultValueFn>,
+}
+
+impl Enum
+{
+    #[inline]
+    pub fn default_value(&self) -> Option<Box<dyn Any>>
+    {
+        Some((self.get_default_value)()?())
+    }
+
+    #[inline]
+    pub fn has_default_value(&self) -> bool
+    {
+        (self.get_default_value)().is_some()
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -169,6 +224,22 @@ pub struct Literal
     pub type_id: TypeId,
     pub ty: LiteralType,
     pub type_name: fn() -> &'static str,
+    pub get_default_value: fn() -> Option<DefaultValueFn>,
+}
+
+impl Literal
+{
+    #[inline]
+    pub fn default_value(&self) -> Option<Box<dyn Any>>
+    {
+        Some((self.get_default_value)()?())
+    }
+
+    #[inline]
+    pub fn has_default_value(&self) -> bool
+    {
+        (self.get_default_value)().is_some()
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -219,7 +290,8 @@ macro_rules! impl_reflection_for_literals {
                     layout: Layout::new::<$literal>(),
                     type_id: TypeId::of::<$literal>(),
                     ty: LiteralType::$literal_type,
-                    type_name: || type_name::<$literal>()
+                    type_name: || type_name::<$literal>(),
+                    get_default_value: || Some(|| Box::new(Self::default()))
                 });
             }
         )*
@@ -288,3 +360,5 @@ impl<Value: Debug> Debug for FnWithDebug<Value>
             .finish()
     }
 }
+
+type DefaultValueFn = fn() -> Box<dyn Any>;