Abri relay exchange reads as serialise, post, parse, then dispatch on the failure document 🟪

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

infrastructure/abri/abri_client.py

@@ -39,51 +39,66 @@ class AbriClient:
                 ("resource_group", RESOURCE_GROUP),
             ],
         )
+
         if isinstance(outcome, AbriRequestRejected):
             return outcome
+
         return self._parse_job_logged(outcome)
 
     def _exchange(
         self, request_type: str, parameters: List[Tuple[str, str]]
     ) -> Union[ET.Element, AbriRequestRejected]:
-        """Send one relay request; return the success root or the typed rejection.
-
-        Shared by all four relay request types: transport failures raise
-        AbriTransportError, ambiguous bodies raise AbriResponseParseError, and
-        only a well-formed <success>false</success> body becomes a rejection.
-        """
-        body = serialise_relay_request(
+        envelope = serialise_relay_request(
             request_type=request_type,
             parameters=parameters,
             username=self._config.username,
             password=self._config.password,
         )
+
+        reply = self._parse_reply(self._post(envelope))
+
+        if self._is_failure_document(reply):
+            return self._parse_rejection(reply)
+
+        return reply
+
+    def _post(self, envelope: bytes) -> bytes:
         try:
-            response = self._session.post(self._config.endpoint_url, data=body)
+            response = self._session.post(self._config.endpoint_url, data=envelope)
             response.raise_for_status()
         except requests.RequestException as error:
             raise AbriTransportError(str(error)) from error
+
+        return response.content
+
+    @staticmethod
+    def _parse_reply(body: bytes) -> ET.Element:
         try:
-            root = ET.fromstring(response.content)
+            return ET.fromstring(body)
         except ET.ParseError as error:
             raise AbriResponseParseError(str(error)) from error
-        if root.tag == "response":
-            return self._parse_rejection(root)
-        return root
+
+    @staticmethod
+    def _is_failure_document(reply: ET.Element) -> bool:
+        return reply.tag == "response"
 
     @staticmethod
     def _parse_job_logged(root: ET.Element) -> JobLogged:
         job_logged = root.find("Jobs/Job_logged")
+
         if job_logged is None:
             raise AbriResponseParseError(
                 "Job_logged element missing from relay response"
             )
+
         job_no = job_logged.get("job_no")
         logged_info = job_logged.get("logged_info")
+
         if job_no is None or logged_info is None:
             raise AbriResponseParseError(
                 "Job_logged element missing job_no or logged_info"
             )
+
         return JobLogged(job_no=job_no, logged_info=logged_info)
 
     @staticmethod
@@ -91,6 +106,8 @@ class AbriClient:
         success = root.findtext("success")
         code = root.findtext("code")
         message = root.findtext("message")
+
         if success != "false" or code is None or message is None:
             raise AbriResponseParseError("malformed relay failure response")
+
         return AbriRequestRejected(code=code, message=message)