feat: add agent that is able to receive messages from UI

Inside the `/message` enpoint we put a message onto the internal event
queue, which gets read by TestAgent. This agent, in turn, logs the
message (temporary behaviour until we implement RI integration).

The name TestAgent is of course temporary, this is just for exploratory
purposes.

ref: N25B-165

src/control_backend/agents/test_agent.py

@@ -1,4 +1,37 @@
+import json
+import logging
 from spade.agent import Agent
+from spade.behaviour import CyclicBehaviour
+import zmq
+
+from control_backend.core.config import settings
+from control_backend.core.zmq_context import context
+from control_backend.schemas.message import Message
+
+logger = logging.getLogger(__name__)
 
 class TestAgent(Agent):
-    pass
+    socket: zmq.Socket
+
+    class ListenBehaviour(CyclicBehaviour):
+        async def run(self):
+            assert self.agent is not None
+            topic, body = await self.agent.socket.recv_multipart()
+            
+            try:
+                message_json = json.loads(body.decode("utf-8"))
+                message = Message.model_validate(message_json)
+                logger.info("Received message \"%s\"", message.message)
+            except Exception as e:
+                logger.error("Error processing message: %s", e)
+
+    async def setup(self):
+        logger.info("Setting up %s", self.jid)
+        self.socket = context.socket(zmq.SUB)
+        self.socket.connect(settings.zmq_settings.internal_comm_address)
+        self.socket.setsockopt(zmq.SUBSCRIBE, b"message")
+
+        b = self.ListenBehaviour()
+        self.add_behaviour(b)
+
+        logger.info("Finished setting up %s", self.jid)

src/control_backend/api/v1/endpoints/message.py

@@ -1,13 +1,23 @@
 from fastapi import APIRouter, Request
 import logging
 
+from zmq import Socket
+
 from control_backend.schemas.message import Message
 
 logger = logging.getLogger(__name__)
 
 router = APIRouter()
 
-# TODO: implement
-@router.post("/message")
+@router.post("/message", status_code=202)
 async def receive_message(message: Message, request: Request):
     logger.info("Received message: %s", message.message)
+
+    topic = b"message"
+    body = message.model_dump_json().encode("utf-8")
+
+    pub_socket: Socket = request.app.state.internal_comm_socket
+
+    pub_socket.send_multipart([topic, body])
+
+    return {"status": "Message received"}

src/control_backend/core/config.py

@@ -1,11 +1,16 @@
-from pydantic import HttpUrl
+from pydantic import BaseModel
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
+class ZMQSettings(BaseModel):
+    internal_comm_address: str = "tcp://localhost:5560"
+
 class Settings(BaseSettings):
     app_title: str = "PepperPlus"
     
     ui_url: str = "http://localhost:5173"
+
+    zmq_settings: ZMQSettings = ZMQSettings()
     
     model_config = SettingsConfigDict(env_file=".env")
     
-settings = Settings()
+settings = Settings()

src/control_backend/core/zmq_context.py

@@ -0,0 +1,3 @@
+from zmq.asyncio import Context
+
+context = Context()

src/control_backend/main.py

@@ -3,10 +3,13 @@ import contextlib
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 import logging
+import zmq
 
 # Internal imports
+from control_backend.agents.test_agent import TestAgent
 from control_backend.api.v1.router import api_router
 from control_backend.core.config import settings
+from control_backend.core.zmq_context import context
 
 logger = logging.getLogger(__name__)
 logging.basicConfig(level=logging.INFO)
@@ -14,6 +17,17 @@ logging.basicConfig(level=logging.INFO)
 @contextlib.asynccontextmanager
 async def lifespan(app: FastAPI):
     logger.info("%s starting up.", app.title)
+
+    # Initiate sockets
+    internal_comm_socket = context.socket(zmq.PUB)
+    internal_comm_address = settings.zmq_settings.internal_comm_address
+    internal_comm_socket.bind(internal_comm_address)
+    app.state.internal_comm_socket = internal_comm_socket
+    logger.info("Internal publishing socket bound to %s", internal_comm_socket)
+
+    # Initiate agents
+    test_agent = TestAgent("test_agent@localhost", "test_agent")
+    await test_agent.start()
     
     yield
     
@@ -34,4 +48,4 @@ app.include_router(api_router, prefix="") # TODO: make prefix /api/v1
 
 @app.get("/")
 async def root():
-    return {"status": "ok"}
+    return {"status": "ok"}