buffered_derive/
lib.rs

1use convert_case::{Case, Casing};
2use proc_macro::TokenStream;
3use quote::{format_ident, quote};
4use syn::{Data, DeriveInput, Fields};
5
6#[proc_macro_attribute]
7pub fn buffered(args: TokenStream, mut input: TokenStream) -> TokenStream {
8    let item = syn::parse::<DeriveInput>(input.clone()).expect("Failed to parse");
9    let ty = match item.data {
10        Data::Struct(x) => x,
11        _ => panic!("Buffed only works for structs"),
12    };
13
14    let (fields, types): (Vec<_>, Vec<_>) = match ty.fields {
15        Fields::Named(x) => x.named,
16        _ => panic!("Buffed only supports named field structs"),
17    }
18    .into_iter()
19    .map(|f| (format_ident!("{}", f.ident.unwrap()), f.ty))
20    .unzip();
21
22    let buffered_name = format_ident!("{}Buffered", item.ident);
23    let buffered_fields_name = format_ident!("{}Fields", item.ident);
24    let buffered_fields_selector_name = format_ident!("{}FieldSelectors", item.ident);
25    let uppercase_fields: Vec<_> = fields
26        .iter()
27        .map(|f| format!("{}", f).to_case(Case::UpperCamel))
28        .map(|f| format_ident!("{}", f))
29        .collect();
30
31    let output: TokenStream = quote! {
32        #[derive(Debug)]
33        struct #buffered_name {
34            #(#fields : Vec<#types>),*
35        }
36
37        #[derive(Debug)]
38        enum #buffered_fields_name {
39            #(#uppercase_fields(#types)),*
40        }
41
42        #[derive(Debug)]
43        enum #buffered_fields_selector_name {
44            #(#uppercase_fields),*
45        }
46
47        impl Buffered for #buffered_name {
48            type Fields = #buffered_fields_name;
49
50            fn push_field(&mut self, field: Self::Fields) -> Result<(), Self::Fields> {
51                match field {
52                    #(Self::Fields::#uppercase_fields(x) => self.#fields.push(x)),*
53                }
54
55                Ok(())
56            }
57        }
58
59        impl #buffered_name {
60            fn new() -> Self {
61                Self {
62                    #(#fields : Vec::new()),*
63                }
64            }
65        }
66
67    }
68    .into();
69
70    input.extend(output);
71    input
72}
buffered_derive/lib.rs

buffered_derive/
lib.rs
