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#![feature(drain_filter)] extern crate proc_macro; use std::collections::HashSet; use proc_macro::TokenStream; use quote::{format_ident, quote}; use syn::{parse_macro_input, parse_quote, FnArg, ItemTrait, PatType, TraitItem}; const SERVER_STREAMING: &str = "server_streaming"; const CLIENT_STREAMING: &str = "client_streaming"; #[proc_macro_attribute] pub fn rpc(_attr: TokenStream, item: TokenStream) -> TokenStream { let mut item = parse_macro_input!(item as ItemTrait); let item_name = item.ident.clone(); let methods: Vec<_> = item .items .iter_mut() .filter_map(|item| match item { TraitItem::Method(method) => { let rpc_attrs: HashSet<_> = method .attrs .drain_filter(|attr| attr.path == parse_quote! { rpc }) .flat_map(|attr| { attr.tokens .to_string() .trim_start_matches('(') .trim_end_matches(')') .to_string() .split(',') .map(|s| s.trim().to_string()) .collect::<Vec<String>>() }) .collect(); Some((method, rpc_attrs)) } _ => None, }) .collect(); let method_variants: Vec<_> = methods .iter() .map(|(method, attrs)| { let name = method.sig.ident.clone(); let method_uri = format!("/{}", name); if method.sig.inputs.len() != 2 { panic!("All RPC methods have to take one argument"); } let call = match method.sig.inputs.iter().nth(1) { Some(FnArg::Typed(PatType { .. })) if attrs.contains(CLIENT_STREAMING) => quote! { self.#name(Box::pin(decode_stream(body))).await }, Some(FnArg::Typed(PatType { ty, .. })) => { quote! {{ let input: #ty = Box::pin(decode_stream(body)) .try_next() .await .context("Could not retrieve request body")? .context("Expected argument")?; self.#name(input).await }} } _ => unreachable!(), }; let method_handler = if attrs.contains(SERVER_STREAMING) { quote! { Box::pin(encode_stream(#call.context("Could not handle the request")?)) } } else { quote! { Box::pin(encode_stream(once(ready(#call)))) } }; quote! { #method_uri => #method_handler } }) .collect(); let client_methods: Vec<_> = methods .iter() .map(|(method, attrs)| { let method_name = method.sig.ident.clone().to_string(); let sig = method.sig.clone(); let call = match method.sig.inputs.iter().nth(1) { Some(FnArg::Typed(PatType { pat, .. })) if attrs.contains(CLIENT_STREAMING) => quote! { self.0.get(#method_name, #pat) }, Some(FnArg::Typed(PatType { pat, .. })) => quote! { self.0.get(#method_name, once(ready(Ok(#pat)))) }, _ => unreachable!(), }; let method_body = if attrs.contains(SERVER_STREAMING) { quote! { Ok(#call.await.context("Could not send request to server")?) } } else { quote! { Ok(#call.await.context("Could not send request to server")? .try_next() .await? .context("Expected message")?) } }; quote! { #sig { use ar_pe_ce::re::*; #method_body } } }) .collect(); item.items.push(parse_quote! { #[ar_pe_ce::re::instrument(skip(self))] async fn handle( self: std::sync::Arc<Self>, req: ar_pe_ce::re::Request<ar_pe_ce::re::Body>) -> ar_pe_ce::Result<ar_pe_ce::re::Response<ar_pe_ce::re::Body>> where Self: Send + Sync{ use ar_pe_ce::{Stream, Error, re::*, encode_stream, decode_stream}; let uri = req.uri().clone(); let uri = uri.path(); let body = req.into_body(); tracing::info!(?uri, "Handling"); let stream: Stream<Bytes> = match uri { #(#method_variants,)* _ => { let mut res = Response::new(Body::empty()); *res.status_mut() = StatusCode::NOT_FOUND; return Ok(res); } }; Ok(Response::new(Body::wrap_stream(stream))) } }); item.items.push(parse_quote! { async fn serve(self, addr: std::net::SocketAddr) -> ar_pe_ce::Result<()> where Self: Sized + Send + Sync + 'static { use ar_pe_ce::{Error, re::*}; use std::sync::Arc; let service = Arc::new(self); let make_svc = make_service_fn(|_conn| { let service = service.clone(); async move { Ok::<_, Error>(service_fn(move |req| service.clone().handle(req))) } }); Server::bind(&addr).http2_only(true).serve(make_svc).await .context("Could not serve the RPC service")?; Ok(()) } }); let client_name = format_ident!("{}Client", item_name); let result = quote! { #[ar_pe_ce::async_trait] #item pub struct #client_name(ar_pe_ce::ClientInner); impl #client_name { pub fn new(url: ar_pe_ce::re::Url) -> Self { Self(ar_pe_ce::ClientInner::new(url)) } } #[ar_pe_ce::async_trait] impl #item_name for #client_name { async fn serve(self, _addr: std::net::SocketAddr) -> ar_pe_ce::Result<()> where Self: Sized + Send + Sync + 'static { unimplemented!(concat!("Please implement ", stringify!(#item_name), " manually. This is a client implementation")) } async fn handle(self: std::sync::Arc<Self>, req: ar_pe_ce::re::Request<ar_pe_ce::re::Body>) -> ar_pe_ce::Result<ar_pe_ce::re::Response<ar_pe_ce::re::Body>> where Self: Send + Sync { unimplemented!(concat!("Please implement ", stringify!(#item_name), " manually. This is a client implementation")) } #(#client_methods)* } }; result.into() }