fix: event parsing iterator

The EventParsingIterator implementation does not parse correctly events when their payload do not have the eventpayload property set. The current behavior is that if said property "eventpayload" is not present then it fallback to extracting the value from the headers, but this is not a reliable method for parsing event streams since seems that not all services uses this pattern to provide the events. One example is the InvokeModelWithResponseStream operation from bedrock-runtime service. To fix this we pretty much followed the specs found in the smithy reference: https://smithy.io/2.0/spec/streaming.html#eventpayload-trait#id6, which explains that when eventpayload and eventheader is not set for any of the members of the shape then, the payload  itself should be considered as the top level shape structure to be parsed.
The test implementation for eventstream  have also been refactored as follow:
 - We now have to specify the rest protocol that the input test data will be using, and based on that protocol we have a factory method to create either a rest xml or rest JSON parser.
 - Instead of validating if a specific member is present to validate if the parsed data type is the correct one, we now validate each parsed member to make sure they are all parsed into the expected data type.

src/Api/Parser/EventParsingIterator.php

@@ -69,37 +69,81 @@ private function parseEvent(array $event)
             if ($event['headers'][':message-type'] === 'error') {
                 return $this->parseError($event);
             }
+
             if ($event['headers'][':message-type'] !== 'event') {
                 throw new ParserException('Failed to parse unknown message type.');
             }
         }
 
-        if (empty($event['headers'][':event-type'])) {
+        $eventType = $event['headers'][':event-type'] ?? null;
+        if (empty($eventType)) {
             throw new ParserException('Failed to parse without event type.');
         }
-        $eventShape = $this->shape->getMember($event['headers'][':event-type']);
-
-        $parsedEvent = [];
-        foreach ($eventShape['members'] as $shape => $details) {
-            if (!empty($details['eventpayload'])) {
-                $payloadShape = $eventShape->getMember($shape);
-                if ($payloadShape['type'] === 'blob') {
-                    $parsedEvent[$shape] = $event['payload'];
+
+        $eventShape = $this->shape->getMember($eventType);
+        $eventPayload = $event['payload'];
+
+        return [
+            $eventType => array_merge(
+                $this->parseEventHeaders($event['headers'], $eventShape),
+                $this->parseEventPayload($eventPayload, $eventShape)
+            )
+        ];
+    }
+
+    /**
+     * @param $headers
+     * @param $eventShape
+     *
+     * @return array
+     */
+    private function parseEventHeaders($headers, $eventShape): array
+    {
+        $parsedHeaders = [];
+        foreach ($eventShape->getMembers() as $memberName => $memberProps) {
+            if (isset($memberProps['eventheader'])) {
+                $parsedHeaders[$memberName] = $headers[$memberName];
+            }
+        }
+
+        return $parsedHeaders;
+    }
+
+    /**
+     * @param $payload
+     * @param $eventShape
+     *
+     * @return array
+     */
+    private function parseEventPayload($payload, $eventShape): array
+    {
+        $parsedPayload = [];
+        foreach ($eventShape->getMembers() as $memberName => $memberProps) {
+            $memberShape = $eventShape->getMember($memberName);
+            if (isset($memberProps['eventpayload'])) {
+                if ($memberShape->getType() === 'blob') {
+                    $parsedPayload[$memberName] = $payload;
                 } else {
-                    $parsedEvent[$shape] = $this->parser->parseMemberFromStream(
-                        $event['payload'],
-                        $payloadShape,
+                    $parsedPayload[$memberName] = $this->parser->parseMemberFromStream(
+                        $payload,
+                        $memberShape,
                         null
                     );
                 }
-            } else {
-                $parsedEvent[$shape] = $event['headers'][$shape];
+
+                break;
             }
         }
 
-        return [
-            $event['headers'][':event-type'] => $parsedEvent
-        ];
+        if (empty($parsedPayload) && !empty($payload->getContents())) {
+            /**
+             * If we did not find a member with an eventpayload trait, then we should deserialize the payload
+             * using the event's shape.
+             */
+            $parsedPayload = $this->parser->parseMemberFromStream($payload, $eventShape, null);
+        }
+
+        return $parsedPayload;
     }
 
     private function parseError(array $event)
@@ -109,4 +153,4 @@ private function parseError(array $event)
             $event['headers'][':error-message']
         );
     }
-}
+}