webrtcd: endpoint for message schema retrieval (#30578)

* Capnp json schema conversion

* Schema get endpoint

* Type annotation for generate_field

* Filter empty services

system/webrtc/schema.py

@@ -0,0 +1,43 @@
+import capnp
+from typing import Union, List, Dict, Any
+
+
+def generate_type(type_walker, schema_walker) -> Union[str, List[Any], Dict[str, Any]]:
+  data_type = next(type_walker)
+  if data_type.which() == 'struct':
+    return generate_struct(next(schema_walker))
+  elif data_type.which() == 'list':
+    _ = next(schema_walker)
+    return [generate_type(type_walker, schema_walker)]
+  elif data_type.which() == 'enum':
+    return "text"
+  else:
+    return str(data_type.which())
+
+
+def generate_struct(schema: capnp.lib.capnp._StructSchema) -> Dict[str, Any]:
+  return {field: generate_field(schema.fields[field]) for field in schema.fields if not field.endswith("DEPRECATED")}
+
+
+def generate_field(field: capnp.lib.capnp._StructSchemaField) -> Union[str, List[Any], Dict[str, Any]]:
+  def schema_walker(field):
+    yield field.schema
+
+    s = field.schema
+    while hasattr(s, 'elementType'):
+      s = s.elementType
+      yield s
+
+  def type_walker(field):
+    yield field.proto.slot.type
+
+    t = field.proto.slot.type
+    while hasattr(getattr(t, t.which()), 'elementType'):
+      t = getattr(t, t.which()).elementType
+      yield t
+
+  if field.proto.which() == "slot":
+    schema_gen, type_gen = schema_walker(field), type_walker(field)
+    return generate_type(type_gen, schema_gen)
+  else:
+    return generate_struct(field.schema)

system/webrtc/webrtcd.py

@@ -23,8 +23,9 @@ from teleoprtc.info import parse_info_from_offer
 
 from openpilot.system.webrtc.device.video import LiveStreamVideoStreamTrack
 from openpilot.system.webrtc.device.audio import AudioInputStreamTrack, AudioOutputSpeaker
+from openpilot.system.webrtc.schema import generate_field
 
-from cereal import messaging
+from cereal import messaging, log
 
 
 class CerealOutgoingMessageProxy:
@@ -205,6 +206,14 @@ async def get_stream(request: web.Request):
   return web.json_response({"sdp": answer.sdp, "type": answer.type})
 
 
+async def get_schema(request: web.Request):
+  services = request.query["services"].split(",")
+  services = [s for s in services if s]
+  assert all(s in log.Event.schema.fields and not s.endswith("DEPRECATED") for s in services), "Invalid service name"
+  schema_dict = {s: generate_field(log.Event.schema.fields[s]) for s in services}
+  return web.json_response(schema_dict)
+
+
 async def on_shutdown(app: web.Application):
   for session in app['streams'].values():
     session.stop()
@@ -223,6 +232,7 @@ def webrtcd_thread(host: str, port: int, debug: bool):
   app['debug'] = debug
   app.on_shutdown.append(on_shutdown)
   app.router.add_post("/stream", get_stream)
+  app.router.add_get("/schema", get_schema)
 
   web.run_app(app, host=host, port=port)