new & improved Control macro is back

Author: sowbug

proc-macros/src/control.rs

@@ -0,0 +1,237 @@
+use convert_case::{Case, Casing};
+use proc_macro::TokenStream;
+use quote::{format_ident, quote};
+use std::collections::HashSet;
+use syn::{parse_macro_input, Data, DataStruct, DeriveInput, Fields, Ident};
+
+use crate::core_crate_name;
+
+// TODO: see
+// https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=03943d1dfbf41bd63878bfccb1c64670
+// for an intriguing bit of code. Came from
+// https://users.rust-lang.org/t/is-implementing-a-derive-macro-for-converting-nested-structs-to-flat-structs-possible/65839/3
+
+pub(crate) fn impl_control_derive(input: TokenStream, primitives: &HashSet<Ident>) -> TokenStream {
+    TokenStream::from({
+        let input = parse_macro_input!(input as DeriveInput);
+        let generics = &input.generics;
+        let data = &input.data;
+        let struct_name = &input.ident;
+        let (_impl_generics, ty_generics, _where_clause) = generics.split_for_impl();
+        let core_crate = format_ident!("{}", core_crate_name());
+
+        // Code adapted from https://blog.turbo.fish/proc-macro-error-handling/
+        // Thank you!
+        let fields = match data {
+            Data::Struct(DataStruct {
+                fields: Fields::Named(fields),
+                ..
+            }) => &fields.named,
+            _ => panic!("this derive macro works only on structs with named fields"),
+        };
+        let attr_fields = fields.into_iter().fold(Vec::default(), |mut v, f| {
+            let attrs: Vec<_> = f
+                .attrs
+                .iter()
+                .filter(|attr| attr.path.is_ident("control"))
+                .collect();
+            if !attrs.is_empty() {
+                match &f.ty {
+                    syn::Type::Path(t) => {
+                        if let Some(ident) = t.path.get_ident() {
+                            v.push((f.ident.as_ref().unwrap().clone(), ident.clone()));
+                        }
+                    }
+                    _ => todo!(),
+                }
+            }
+            v
+        });
+
+        // FOO_SIZE = 3; self.foo contains 3 controlled fields
+        fn size_const_id(ident: &Ident) -> Ident {
+            format_ident!("{}_SIZE", ident.to_string().to_case(Case::UpperSnake))
+        }
+        // FOO_NAME = "foo"; self.foo is addressable by "foo"
+        fn name_const_id(ident: &Ident) -> Ident {
+            let ident_upper = ident.to_string().to_case(Case::UpperSnake);
+            format_ident!("{}_NAME", ident_upper)
+        }
+        // FOO_INDEX = 5; address the foo element with index 5 (and maybe higher if node)
+        fn index_const_id(ident: &Ident) -> Ident {
+            let ident_upper = ident.to_string().to_case(Case::UpperSnake);
+            format_ident!("{}_INDEX", ident_upper)
+        }
+        // FOO_RANGE_END = 7; address foo's flattened elements with indexes 5, 6, and 7.
+        fn index_range_end_const_id(ident: &Ident) -> Ident {
+            let ident_upper = ident.to_string().to_case(Case::UpperSnake);
+            format_ident!("{}_RANGE_END", ident_upper)
+        }
+
+        let mut size_const_ids = Vec::default();
+        let mut size_const_values = Vec::default();
+        attr_fields.iter().for_each(|(ident, ident_type)| {
+            let size_const_name = size_const_id(ident);
+            size_const_ids.push(size_const_name.clone());
+
+            if primitives.contains(ident_type) {
+                size_const_values.push(quote! { 1 });
+            } else {
+                size_const_values.push(quote! { #ident_type::STRUCT_SIZE });
+            }
+        });
+        let size_const_body = quote! {
+            #( const #size_const_ids: usize = #size_const_values; )*
+        };
+
+        let mut index_const_ids = Vec::default();
+        let mut index_const_range_end_ids = Vec::default();
+        let mut index_const_values = Vec::default();
+
+        // This loop calculates each field's index.
+        //
+        // Since proc macros don't have access to any other information than the
+        // struct TokenStream, we can't incorporate any sub-structure
+        // information (such as how big the field is) except by referring to
+        // consts. In other words, if Struct contains EmbeddedStruct, we can't
+        // ask how big EmbeddedStruct is, but we can refer to
+        // EmbeddedStruct::STRUCT_SIZE and let the compiler figure out that
+        // value during the build.
+        //
+        // Thus, a field's index will always be either (1) zero if it's the
+        // first, or (2) the index of the prior field + the size of the prior
+        // field. So we need to keep track of the prior field name, which
+        // enables us to build up the current value from the prior one.
+        let mut prior_ident: Option<&Ident> = None;
+        attr_fields.iter().for_each(|(ident, _)| {
+            index_const_ids.push(index_const_id(ident));
+            index_const_range_end_ids.push(index_range_end_const_id(ident));
+            if let Some(prior) = prior_ident {
+                let prior_index_const_name = index_const_id(prior);
+                let prior_size_const_name = size_const_id(prior);
+                index_const_values
+                    .push(quote! { Self::#prior_index_const_name + Self::#prior_size_const_name });
+            } else {
+                index_const_values.push(quote! { 0 });
+            }
+            prior_ident = Some(ident);
+        });
+        let mut name_const_ids = Vec::default();
+        let mut name_const_values = Vec::default();
+        attr_fields.iter().for_each(|(ident, _)| {
+            let name_const = name_const_id(ident);
+            name_const_ids.push(name_const.clone());
+            name_const_values.push(ident.to_string().to_case(Case::Kebab));
+        });
+
+        let main_const_body = quote! {
+            #( pub const #index_const_ids: usize = #index_const_values; )*
+            #( pub const #name_const_ids: &str = #name_const_values; )*
+        };
+        let range_const_body = quote! {
+            #( pub const #index_const_range_end_ids: usize = #index_const_values + #size_const_values - 1; )*
+        };
+        let struct_size_const_body = quote! {
+            pub const STRUCT_SIZE: usize = 0 + #( Self::#size_const_ids )+* ;
+        };
+
+        let mut id_bodies = Vec::default();
+        let mut setter_bodies = Vec::default();
+        attr_fields.iter().for_each(|(ident, ident_type)| {
+            let id = ident.to_string().to_case(Case::Kebab);
+            if primitives.contains(ident_type) {
+                let name_const = format_ident!("set_{}", ident);
+                id_bodies.push(quote! {Some(#id.to_string())});
+                setter_bodies.push(quote! {self.#name_const(value.into());});
+            } else {
+                let field_index_name = index_const_id(ident);
+                let name_const = name_const_id(ident);
+                id_bodies.push(quote! { Some(format!("{}-{}", Self::#name_const, self.#ident.control_name_for_index(index - Self::#field_index_name).unwrap()))});
+                setter_bodies
+                    .push(quote! {self.#ident.control_set_param_by_index(index - Self::#field_index_name, value);});
+            }
+        });
+        let control_name_for_index_body = quote! {
+            fn control_name_for_index(&self, index: usize) -> Option<String> {
+                match index {
+                    #( Self::#index_const_ids..=Self::#index_const_range_end_ids => {#id_bodies} ),*
+                    _ => {None},
+                }
+            }
+        };
+        let control_set_param_by_index_bodies = quote! {
+            fn control_set_param_by_index(&mut self, index: usize, value: #core_crate::control::F32ControlValue) {
+                match index {
+                    #( Self::#index_const_ids..=Self::#index_const_range_end_ids => {#setter_bodies} ),*
+                    _ => {},
+                }
+            }
+        };
+
+        // These need to be separate vecs because we divide the fields into
+        // groups of maybe different sizes, which is a repetitions no-no.
+        let mut leaf_names = Vec::default();
+        let mut leaf_indexes = Vec::default();
+        let mut node_names = Vec::default();
+        let mut node_indexes = Vec::default();
+        let mut node_fields = Vec::default();
+        let mut node_field_lens = Vec::default();
+        attr_fields.iter().for_each(|(ident, ident_type)| {
+            let const_name = name_const_id(ident);
+            let field_index_name = index_const_id(ident);
+            if primitives.contains(ident_type) {
+                leaf_names.push(quote! { Self::#const_name });
+                leaf_indexes.push(quote! { Self::#field_index_name });
+            } else {
+                node_names.push(quote! { Self::#const_name });
+                node_indexes.push(quote! { Self::#field_index_name });
+                node_fields.push(ident);
+                // Includes the dash at the end that separates the field parts in the ID
+                let node_field_len = ident.to_string().len() + 1;
+                node_field_lens.push(quote! {#node_field_len});
+            }
+        });
+        let control_index_for_name_body = quote! {
+            fn control_index_for_name(&self, name: &str) -> Option<usize> {
+                match name {
+                    #( #leaf_names => Some(#leaf_indexes), )*
+                    _ => {
+                        #(
+                            if name.starts_with(#node_names) {
+                                if let Some(r) = self.#node_fields.control_index_for_name(&name[#node_field_lens..]) {
+                                    return Some(r + #node_indexes)
+                                }
+                            }
+                        )*
+                        None
+                    },
+                }
+            }
+        };
+
+        let quote = quote! {
+            #[automatically_derived]
+            impl #generics #struct_name #ty_generics {
+                #size_const_body
+                #main_const_body
+                #range_const_body
+                #struct_size_const_body
+            }
+            #[automatically_derived]
+            impl #generics #core_crate::traits::Controllable for #struct_name #ty_generics {
+                fn control_index_count(&self) -> usize { Self::STRUCT_SIZE }
+                fn control_set_param_by_name(&mut self, name: &str, value: #core_crate::control::F32ControlValue) {
+                    if let Some(index) = self.control_index_for_name(name) {
+                        self.control_set_param_by_index(index, value);
+                    } else {
+                        eprintln!("Warning: couldn't set param named '{}'", name);
+                    }
+                }
+                #control_name_for_index_body
+                #control_index_for_name_body
+                #control_set_param_by_index_bodies
+            }
+        };
+        quote
+    })
+}

proc-macros/src/lib.rs

@@ -2,15 +2,18 @@
 
 //! This crate provides macros that make Entity development easier.
 
+use control::impl_control_derive;
 use everything::parse_and_generate_everything;
 use nano::impl_nano_derive;
 use proc_macro::TokenStream;
 use proc_macro_crate::crate_name;
 use quote::{format_ident, quote};
-use syn::{parse_macro_input, DeriveInput};
+use std::collections::HashSet;
+use syn::{parse_macro_input, DeriveInput, Ident};
 use uid::impl_uid_derive;
 use views::parse_and_generate_views;
 
+mod control;
 mod everything;
 mod nano;
 mod uid;
@@ -49,6 +52,45 @@ pub fn derive_views(input: TokenStream) -> TokenStream {
     ))
 }
 
+/// field types that don't recurse further for #[derive(Control)] purposes
+fn make_primitives() -> HashSet<Ident> {
+    vec![
+        "BipolarNormal",
+        "FrequencyHz",
+        "Normal",
+        "ParameterType",
+        "Ratio",
+        "String",
+        "Waveform",
+        "bool",
+        "char",
+        "f32",
+        "f64",
+        "i128",
+        "i16",
+        "i32",
+        "i64",
+        "i8",
+        "u128",
+        "u16",
+        "u32",
+        "u64",
+        "u8",
+        "usize",
+    ]
+    .into_iter()
+    .fold(HashSet::default(), |mut hs, e| {
+        hs.insert(format_ident!("{}", e));
+        hs
+    })
+}
+
+/// The [Control] macro derives the code that allows automation (one entity's output driving another entity's control).
+#[proc_macro_derive(Control, attributes(control))]
+pub fn derive_control(input: TokenStream) -> TokenStream {
+    impl_control_derive(input, &make_primitives())
+}
+
 // Some of the code generated in these macros uses the groove-core crate, but
 // groove-core also uses this proc-macro lib. So we need to correct the
 // reference to groove-core to sometimes be just `crate`.