From 316d02b72b08bd3a06806fab1795861ed376ec0e Mon Sep 17 00:00:00 2001
From: bitfl0wer <florian@pro-weber.com>
Date: Tue, 15 Aug 2023 12:13:49 +0200
Subject: [PATCH] Add macro and attributes for automatic watching of Composite
 structs and their components

---
 chorus-macros/src/lib.rs | 97 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/chorus-macros/src/lib.rs b/chorus-macros/src/lib.rs
index c8d5e87..7ae2e83 100644
--- a/chorus-macros/src/lib.rs
+++ b/chorus-macros/src/lib.rs
@@ -1,5 +1,6 @@
 use proc_macro::TokenStream;
 use quote::quote;
+use syn::{parse_macro_input, Data, DeriveInput, Field, Fields, FieldsNamed};
 
 #[proc_macro_derive(Updateable)]
 pub fn updateable_macro_derive(input: TokenStream) -> TokenStream {
@@ -16,3 +17,99 @@ pub fn updateable_macro_derive(input: TokenStream) -> TokenStream {
     }
     .into()
 }
+
+#[proc_macro_attribute]
+pub fn observe_option(_args: TokenStream, input: TokenStream) -> TokenStream {
+    input
+}
+
+#[proc_macro_attribute]
+pub fn observe_option_vec(_args: TokenStream, input: TokenStream) -> TokenStream {
+    input
+}
+
+#[proc_macro_attribute]
+pub fn observe(_args: TokenStream, input: TokenStream) -> TokenStream {
+    input
+}
+
+#[proc_macro_attribute]
+pub fn observe_vec(_args: TokenStream, input: TokenStream) -> TokenStream {
+    input
+}
+
+#[proc_macro_derive(
+    Composite,
+    attributes(observe_option_vec, observe_option, observe, observe_vec)
+)]
+pub fn composite_derive(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    let process_field = |field: &Field| {
+        let field_name = &field.ident;
+        let attrs = &field.attrs;
+
+        let observe_option = attrs
+            .iter()
+            .any(|attr| attr.path().is_ident("observe_option"));
+        let observe_option_vec = attrs
+            .iter()
+            .any(|attr| attr.path().is_ident("observe_option_vec"));
+        let observe = attrs.iter().any(|attr| attr.path().is_ident("observe"));
+        let observe_vec = attrs.iter().any(|attr| attr.path().is_ident("observe_vec"));
+
+        let field_is_arc_rwlock = if let syn::Type::Path(type_path) = &field.ty {
+            type_path.path.segments.last().map_or(false, |segment| {
+                segment.ident == "Arc" || segment.ident == "RwLock"
+            })
+        } else {
+            false
+        };
+
+        if field_is_arc_rwlock {
+            match (observe_option, observe_option_vec, observe, observe_vec) {
+                (true, _, _, _) => quote! {
+                    #field_name: option_observe_fn(self.#field_name)
+                },
+                (_, true, _, _) => quote! {
+                    #field_name: option_vec_observe_fn(self.#field_name)
+                },
+                (_, _, true, _) => quote! {
+                    #field_name: value_observe_fn(self.#field_name)
+                },
+                (_, _, _, true) => quote! {
+                    #field_name: vec_observe_fn(self.#field_name)
+                },
+                _ => quote! {
+                    #field_name: self.#field_name
+                },
+            }
+        } else {
+            panic!("Fields must be of type Arc<RwLock<T: Updateable>>");
+        }
+    };
+
+    match &input.data {
+        Data::Struct(data) => match &data.fields {
+            Fields::Named(FieldsNamed { named, .. }) => {
+                let field_exprs = named.iter().map(process_field);
+
+                let ident = &input.ident;
+
+                let expanded = quote! {
+                    impl<T: Updateable> Composite<T> for #ident {
+                        fn watch_whole(self) -> Self {
+                            Self {
+                                #(#field_exprs,)*
+                            }
+                        }
+                    }
+                };
+
+                TokenStream::from(expanded)
+            }
+            _ => panic!("Composite derive macro only supports named fields"),
+        },
+        _ => panic!("Composite derive macro only supports structs"),
+    }
+}