ireko/paramacro/src/lib.rs

extern crate proc_macro;

use proc_macro::TokenStream;
use quote::{quote, ToTokens};
use syn::{parse_macro_input, Expr, Fields, Item, Lit};

// TODO: clean up this mess.

/// Helps read and write serialized structs. These are structs that have named fields with known types.
/// Note: This adds a hidden "None" at the end of the struct as well.
#[proc_macro_attribute]
pub fn serialized_struct(_metadata: TokenStream, input: TokenStream)
                  -> TokenStream {
    let mut input = syn::parse_macro_input!(input as syn::ItemStruct);
    let Lit::Str(struct_name) = syn::parse_macro_input!(_metadata as syn::Lit) else {
        panic!("This must be given a name!")
    };

    let mut field_types = vec![];
    let mut field_idents = vec![];
    let mut field_names = vec![];

    for field in &mut input.fields {
        let our_custom = &field.attrs[0];
        let our_custom_name = our_custom.meta.require_name_value().unwrap();
        let our_custom_name = match &our_custom_name.value {
            Expr::Lit(_0) => {
                match &_0.lit {
                    Lit::Str(_0) => {
                        Some(_0.value())
                    }
                    _ => None
                }
            }
            _ => None
        }.unwrap();
        field.attrs.clear();
        field_types.push(field.ty.clone());
        field_idents.push(field.ident.clone());
        field_names.push(our_custom_name.clone());
        let field_tokens = field.to_token_stream();
        let new_field_token_stream = quote! {
            #[br(parse_with = crate::structs::read_struct_field, args(#our_custom_name))]
            #[bw(write_with = crate::structs::write_struct_field, args(#our_custom_name))]
            #field_tokens
        };
        let buffer = ::syn::parse::Parser::parse2(
            syn::Field::parse_named,
            new_field_token_stream,
        ).unwrap();
        *field = buffer;
    }

    // Add "None" field
    let none_field_stream = quote! {
        #[br(temp)]
        #[bw(calc = crate::structs::GenericProperty { property_name: "None".to_string(), type_name: "".to_string(), key: None } )]
        none_field: crate::structs::GenericProperty
    };
    let buffer = ::syn::parse::Parser::parse2(
        syn::Field::parse_named,
        none_field_stream,
    ).unwrap();
    match &mut input.fields {
        Fields::Named(_0) => {
            _0.named.push(buffer)
        }
        _ => {}
    }

    let id = &input.ident;

    let output = quote! {
        #[binrw]
        #input

        #[automatically_derived]
        impl crate::structs::PropertyBase for #id {
            fn type_name() -> &'static str {
                return "StructProperty";
            }

            fn struct_name() -> Option<&'static str> {
                return Some(#struct_name);
            }

            fn size_in_bytes(&self) -> u32 {
                #( #field_types::size_in_bytes(&self.#field_idents) )+* + #( (crate::structs::calc_struct_field_prelude_byte_size(stringify!(#field_types), #field_names, #field_types::struct_name()) ) )+* + 9 // for "none" field
            }
        }
    };

    output.into_token_stream().into()
}

/// Denotes a field with a known name.
#[proc_macro_attribute]
pub fn serialized_field(attr: TokenStream, input: TokenStream) -> TokenStream {
    let input2 = parse_macro_input!(input as Item);

    let output = quote! {
        #[binrw]
        #input2
    };

    output.into_token_stream().into()
}