fix(event-stream): handle initial response 🚧

packages/eventstream-serde-universal/src/EventStreamMarshaller.ts

@@ -11,11 +11,6 @@ import { Decoder, Encoder, EventStreamMarshaller as IEventStreamMarshaller, Mess
 import { getChunkedStream } from "./getChunkedStream";
 import { getMessageUnmarshaller } from "./getUnmarshalledStream";
 
-/**
- * @internal
- */
-export interface EventStreamMarshaller extends IEventStreamMarshaller {}
-
 /**
  * @internal
  */
@@ -27,7 +22,7 @@ export interface EventStreamMarshallerOptions {
 /**
  * @internal
  */
-export class EventStreamMarshaller {
+export class EventStreamMarshaller implements IEventStreamMarshaller {
   private readonly eventStreamCodec: EventStreamCodec;
   private readonly utfEncoder: Encoder;
 
@@ -41,11 +36,9 @@ export class EventStreamMarshaller {
     deserializer: (input: Record<string, Message>) => Promise<T>
   ): AsyncIterable<T> {
     const inputStream = getChunkedStream(body);
-    // @ts-expect-error Type 'SmithyMessageDecoderStream<Record<string, any>>' is not assignable to type 'AsyncIterable<T>'
-    return new SmithyMessageDecoderStream({
+    return new SmithyMessageDecoderStream<T>({
       messageStream: new MessageDecoderStream({ inputStream, decoder: this.eventStreamCodec }),
-      // @ts-expect-error Type 'T' is not assignable to type 'Record<string, any>'
-      deserializer: getMessageUnmarshaller(deserializer, this.utfEncoder),
+      deserializer: getMessageUnmarshaller<any>(deserializer, this.utfEncoder),
     });
   }
 

packages/eventstream-serde-universal/src/getUnmarshalledStream.ts

@@ -61,9 +61,7 @@ export function getMessageUnmarshaller<T extends Record<string, any>>(
       const event = {
         [message.headers[":event-type"].value as string]: message,
       };
-      const deserialized = await deserializer(event);
-      if (deserialized.$unknown) return;
-      return deserialized;
+      return deserializer(event);
     } else {
       throw Error(`Unrecognizable event type: ${message.headers[":event-type"].value}`);
     }

packages/eventstream-serde-universal/src/initialRequestResponse.ts

@@ -0,0 +1,36 @@
+/**
+ * Peeks the first frame of the async iterable and writes the values into
+ * the container if it is an initial-response event.
+ *
+ * @internal
+ *
+ * @param container - write destination for initial-response.
+ * @param responseIterable - the response event stream.
+ */
+export async function writeResponse<T>(
+  container: Record<string, any>,
+  responseIterable: AsyncIterable<T>
+): Promise<AsyncIterable<T>> {
+  const asyncIterator = responseIterable[Symbol.asyncIterator]();
+  // todo: handle empty iterator or timeout.
+  const firstFrame = await asyncIterator.next();
+  if (firstFrame.value.$unknown?.["initial-response"]) {
+    console.log("assigned initial response into container", {
+      initialResponse: firstFrame.value.$unknown["initial-response"],
+    });
+    Object.assign(container, firstFrame.value.$unknown["initial-response"]);
+    return {
+      [Symbol.asyncIterator]: () => ({
+        next: asyncIterator.next.bind(asyncIterator),
+      }),
+    };
+  }
+  return responseIterable;
+}
+
+/**
+ * @internal
+ */
+export async function writeRequest<T>() {
+  throw new Error("not implemented");
+}

packages/types/src/eventStream.ts

@@ -119,7 +119,7 @@ export interface EventStreamMarshallerSerFn<StreamType> {
  * @public
  *
  * An interface which provides functions for serializing and deserializing binary event stream
- * to/from corresponsing modeled shape.
+ * to/from corresponding modeled shape.
  */
 export interface EventStreamMarshaller<StreamType = any> {
   deserialize: EventStreamMarshallerDeserFn<StreamType>;

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/EventStreamGenerator.java

@@ -48,7 +48,7 @@
 import software.amazon.smithy.utils.SmithyUnstableApi;
 
 /**
- * Evnetstream code generator.
+ * Event stream code generator.
  */
 @SmithyUnstableApi
 public class EventStreamGenerator {