refactor: centralize ndjson streaming transport

app/backend/application.py

@@ -1020,16 +1020,6 @@ class RequestHandler(
             return
         self.send_json({"error": "Not found"}, HTTPStatus.NOT_FOUND)
 
-
-
-    def _write_stream_event(self, payload: dict[str, Any]) -> None:
-        self.wfile.write(
-            (json.dumps(payload, ensure_ascii=False, separators=(",", ":")) + "\n").encode("utf-8")
-        )
-        self.wfile.flush()
-
-
-
     def save_reason(self) -> None:
         try:
             body = self.read_json_body()

app/backend/features/mentor/http.py

@@ -14,19 +14,4 @@ class MentorHttpMixin:
         except (ValueError, json.JSONDecodeError) as exc:
             self.send_json({"error": str(exc)}, HTTPStatus.BAD_REQUEST)
             return
-        self.send_response(HTTPStatus.OK)
-        self.send_header("Content-Type", "application/x-ndjson; charset=utf-8")
-        self.send_header("Cache-Control", "no-cache, no-transform")
-        self.send_header("X-Accel-Buffering", "no")
-        self.send_header("Connection", "close")
-        self.end_headers()
-        try:
-            for event in stream:
-                self._write_stream_event(event)
-            self._write_stream_event({"type": "done"})
-        except (ValueError, MentorAgentError) as exc:
-            self._write_stream_event({"type": "error", "error": str(exc)})
-        except (BrokenPipeError, ConnectionResetError):
-            pass
-        finally:
-            self.close_connection = True
+        self.send_ndjson_stream(stream, (ValueError, MentorAgentError))

app/backend/features/review/http.py

@@ -26,22 +26,8 @@ class ReviewHttpMixin:
         except (ValueError, json.JSONDecodeError) as exc:
             self.send_json({"error": str(exc)}, HTTPStatus.BAD_REQUEST)
             return
-        self.send_response(HTTPStatus.OK)
-        self.send_header("Content-Type", "application/x-ndjson; charset=utf-8")
-        self.send_header("Cache-Control", "no-cache, no-transform")
-        self.send_header("X-Accel-Buffering", "no")
-        self.send_header("Connection", "close")
-        self.end_headers()
-        try:
-            for chunk in stream:
-                self._write_stream_event({"type": "delta", "content": chunk})
-            self._write_stream_event({"type": "done"})
-        except (ValueError, ReviewAssistantError) as exc:
-            self._write_stream_event({"type": "error", "error": str(exc)})
-        except (BrokenPipeError, ConnectionResetError):
-            pass
-        finally:
-            self.close_connection = True
+        events = ({"type": "delta", "content": chunk} for chunk in stream)
+        self.send_ndjson_stream(events, (ValueError, ReviewAssistantError))
 
     def save_watchlist(self) -> None:
         try:

app/backend/http/handler.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import json
 import mimetypes
 import secrets
+from collections.abc import Iterable
 from http import HTTPStatus
 from http.cookies import SimpleCookie
 from typing import Any
@@ -142,5 +143,33 @@ class HttpTransportMixin:
         self.end_headers()
         self.wfile.write(content)
 
+    def _write_stream_event(self, payload: dict[str, Any]) -> None:
+        self.wfile.write(
+            (json.dumps(payload, ensure_ascii=False, separators=(",", ":")) + "\n").encode("utf-8")
+        )
+        self.wfile.flush()
+
+    def send_ndjson_stream(
+        self,
+        events: Iterable[dict[str, Any]],
+        error_types: tuple[type[Exception], ...],
+    ) -> None:
+        self.send_response(HTTPStatus.OK)
+        self.send_header("Content-Type", "application/x-ndjson; charset=utf-8")
+        self.send_header("Cache-Control", "no-cache, no-transform")
+        self.send_header("X-Accel-Buffering", "no")
+        self.send_header("Connection", "close")
+        self.end_headers()
+        try:
+            for event in events:
+                self._write_stream_event(event)
+            self._write_stream_event({"type": "done"})
+        except error_types as exc:
+            self._write_stream_event({"type": "error", "error": str(exc)})
+        except (BrokenPipeError, ConnectionResetError):
+            pass
+        finally:
+            self.close_connection = True
+
     def log_message(self, format_string: str, *args: Any) -> None:
         print(f"[{self.log_date_time_string()}] {format_string % args}")