From c642c9716e463ee33f41a30ab5a0d4e6380f855d Mon Sep 17 00:00:00 2001
From: Konstantin Tcepliaev <f355@f355.org>
Date: Thu, 5 Mar 2020 14:54:06 +0000
Subject: [PATCH] support asynchronous responses to unary requests.

---
 src/grpcbox_stream.erl | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/grpcbox_stream.erl b/src/grpcbox_stream.erl
index 76f71ba..2302da5 100644
--- a/src/grpcbox_stream.erl
+++ b/src/grpcbox_stream.erl
@@ -8,6 +8,7 @@
 
 -export([send/2,
          send/3,
+         unary_reply/2,
          send_headers/2,
          add_headers/2,
          add_trailers/2,
@@ -50,6 +51,7 @@
                 resp_trailers=[]    :: list(),
                 headers_sent=false  :: boolean(),
                 trailers_sent=false :: boolean(),
+                async_unary=false   :: boolean(),
                 unary_interceptor   :: fun() | undefined,
                 stream_interceptor  :: fun() | undefined,
                 stream_id           :: stream_id(),
@@ -260,6 +262,8 @@ handle_unary(Ctx, Message, State=#state{unary_interceptor=UnaryInterceptor,
         {ok, Response, Ctx2} ->
             State1 = from_ctx(Ctx2),
             send(false, Response, State1);
+        {noreply, Ctx2} ->
+            (from_ctx(Ctx2))#state{async_unary=true};
         E={grpc_error, _} ->
             throw(E)
     end.
@@ -268,6 +272,9 @@ on_end_stream(State) ->
     on_end_stream_(State),
     {ok, State}.
 
+
+on_end_stream_(#state{async_unary=true}) ->
+    ok;
 on_end_stream_(#state{input_ref=Ref,
                       callback_pid=Pid,
                       method=#method{input={_Input, true},
@@ -365,10 +372,16 @@ ctx(#state{handler=Pid}) ->
 ctx(#state{handler=Pid}, Ctx) ->
     h2_stream:call(Pid, {ctx, Ctx}).
 
+unary_reply(Message, Ctx) ->
+    #state{handler=Pid} = from_ctx(Ctx),
+    h2_stream:call(Pid, {unary_reply, Message}).
+
 handle_call(ctx, State=#state{ctx=Ctx}) ->
     {ok, Ctx, State};
 handle_call({ctx, Ctx}, State) ->
-    {ok, ok, State#state{ctx=Ctx}}.
+    {ok, ok, State#state{ctx=Ctx}};
+handle_call({unary_reply, Message}, State) ->
+    {ok, ok, end_stream(send(false, Message, State))}.
 
 handle_info({add_headers, Headers}, State) ->
     update_headers(Headers, State);