lemmy/crates/apub_lib_derive/src/lib.rs

130 lines
3.8 KiB
Rust

use proc_macro2::{TokenStream, TokenTree};
use quote::quote;
use syn::{parse_macro_input, Attribute, Data, DeriveInput, Fields::Unnamed, Ident, Variant};
/// Generates implementation ActivityHandler for an enum, which looks like the following (handling
/// all enum variants).
///
/// Based on this code:
/// ```ignore
/// #[derive(serde::Deserialize, serde::Serialize, ActivityHandler)]
/// #[serde(untagged)]
/// pub enum PersonInboxActivities {
/// CreateNote(CreateNote),
/// UpdateNote(UpdateNote),
/// ```
/// It will generate this:
/// ```ignore
/// impl ActivityHandler for PersonInboxActivities {
///
/// async fn verify(
/// &self,
/// context: &LemmyContext,
/// request_counter: &mut i32,
/// ) -> Result<(), LemmyError> {
/// match self {
/// PersonInboxActivities::CreateNote(a) => a.verify(context, request_counter).await,
/// PersonInboxActivities::UpdateNote(a) => a.verify(context, request_counter).await,
/// }
/// }
///
/// async fn receive(
/// &self,
/// context: &LemmyContext,
/// request_counter: &mut i32,
/// ) -> Result<(), LemmyError> {
/// match self {
/// PersonInboxActivities::CreateNote(a) => a.receive(context, request_counter).await,
/// PersonInboxActivities::UpdateNote(a) => a.receive(context, request_counter).await,
/// }
/// }
/// fn common(&self) -> &ActivityCommonFields {
/// match self {
/// PersonInboxActivities::CreateNote(a) => a.common(),
/// PersonInboxActivities::UpdateNote(a) => a.common(),
/// }
/// }
///
/// ```
#[proc_macro_derive(ActivityHandler, attributes(activity_handler))]
pub fn derive_activity_handler(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let attrs: Vec<&Attribute> = input
.attrs
.iter()
.filter(|attr| attr.path.is_ident("activity_handler"))
.collect();
let attrs: &Vec<TokenStream> = &attrs
.first()
.expect("Could not decode first attribute from token stream")
.tokens
.clone()
.into_iter()
.map(|t| {
if let TokenTree::Group(g) = t {
g.stream()
} else {
panic!()
}
})
.collect();
let attrs = attrs.first();
let enum_name = input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let enum_variants = if let Data::Enum(d) = input.data {
d.variants
} else {
unimplemented!()
};
let body_verify = quote! {a.verify(context, request_counter).await};
let impl_verify = enum_variants
.iter()
.map(|v| generate_match_arm(&enum_name, v, &body_verify));
let body_receive = quote! {a.receive(context, request_counter).await};
let impl_receive = enum_variants
.iter()
.map(|v| generate_match_arm(&enum_name, v, &body_receive));
let expanded = quote! {
#[async_trait::async_trait(?Send)]
impl #impl_generics lemmy_apub_lib::traits::ActivityHandler for #enum_name #ty_generics #where_clause {
type DataType = #attrs;
async fn verify(
&self,
context: &lemmy_apub_lib::data::Data<Self::DataType>,
request_counter: &mut i32,
) -> Result<(), lemmy_utils::LemmyError> {
match self {
#(#impl_verify)*
}
}
async fn receive(
self,
context: &lemmy_apub_lib::data::Data<Self::DataType>,
request_counter: &mut i32,
) -> Result<(), lemmy_utils::LemmyError> {
match self {
#(#impl_receive)*
}
}
}
};
expanded.into()
}
fn generate_match_arm(enum_name: &Ident, variant: &Variant, body: &TokenStream) -> TokenStream {
let id = &variant.ident;
match &variant.fields {
Unnamed(_) => {
quote! {
#enum_name::#id(a) => #body,
}
}
_ => unimplemented!(),
}
}