1 files changed, 83 insertions, 0 deletions
diff --git a/syrette_macros/src/factory_type_alias.rs b/syrette_macros/src/factory_type_alias.rs
new file mode 100644
index 0000000..82e2315
--- /dev/null
+++ b/syrette_macros/src/factory_type_alias.rs
@@ -0,0 +1,83 @@
+use syn::parse::{Parse, ParseStream};
+use syn::{GenericArgument, ItemType, Path, Type, TypeParamBound, TypeTuple};
+
+pub struct FactoryTypeAlias
+{
+    pub type_alias: ItemType,
+    pub factory_interface: Path,
+    pub arg_types: TypeTuple,
+    pub return_type: Type,
+}
+
+impl Parse for FactoryTypeAlias
+{
+    fn parse(input: ParseStream) -> syn::Result<Self>
+    {
+        let type_alias = match input.parse::<ItemType>() {
+            Ok(type_alias) => Ok(type_alias),
+            Err(_) => Err(input.error("Expected a type alias")),
+        }?;
+
+        let aliased_trait = match &type_alias.ty.as_ref() {
+            Type::TraitObject(alias_type) => Ok(alias_type),
+            &_ => Err(input.error("Expected the aliased type to be a trait")),
+        }?;
+
+        if aliased_trait.bounds.len() != 1 {
+            return Err(input.error("Expected the aliased trait to have a single bound."));
+        }
+
+        let bound_path = &match aliased_trait.bounds.first().unwrap() {
+            TypeParamBound::Trait(trait_bound) => Ok(trait_bound),
+            &_ => {
+                Err(input.error("Expected the bound of the aliased trait to be a trait"))
+            }
+        }?
+        .path;
+
+        if bound_path.segments.is_empty()
+            || bound_path.segments.last().unwrap().ident != "IFactory"
+        {
+            return Err(input
+                .error("Expected the bound of the aliased trait to be 'dyn IFactory'"));
+        }
+
+        let angle_bracketed_args = match &bound_path.segments.last().unwrap().arguments {
+            syn::PathArguments::AngleBracketed(angle_bracketed_args) => {
+                Ok(angle_bracketed_args)
+            }
+            &_ => {
+                Err(input.error("Expected angle bracketed arguments for 'dyn IFactory'"))
+            }
+        }?;
+
+        let arg_types = match &angle_bracketed_args.args[0] {
+            GenericArgument::Type(arg_types_type) => match arg_types_type {
+                Type::Tuple(arg_types) => Ok(arg_types),
+                &_ => Err(input.error(concat!(
+                    "Expected the first angle bracketed argument ",
+                    "of 'dyn IFactory' to be a type tuple"
+                ))),
+            },
+            &_ => Err(input.error(concat!(
+                "Expected the first angle bracketed argument ",
+                "of 'dyn IFactory' to be a type"
+            ))),
+        }?;
+
+        let return_type = match &angle_bracketed_args.args[1] {
+            GenericArgument::Type(arg_type) => Ok(arg_type),
+            &_ => Err(input.error(concat!(
+                "Expected the second angle bracketed argument ",
+                "of 'dyn IFactory' to be a type"
+            ))),
+        }?;
+
+        Ok(Self {
+            type_alias: type_alias.clone(),
+            factory_interface: bound_path.clone(),
+            arg_types: arg_types.clone(),
+            return_type: return_type.clone(),
+        })
+    }
+}