Added Ruff linting

pyproject.toml

@@ -0,0 +1,28 @@
+[tool.ruff]
+line-length = 120
+target-version = "py312"
+[tool.ruff.lint]
+select = [
+	"E", "F", # pycodestyle errors, pyflakes (unused imports/variables, undefined names)
+	"I", # import sorting (replaces isort)
+	"B", # bugbear: likely bugs
+	"ASYNC", # async mistakes
+	"RUF006", # un-referenced asyncio.create_task (tasks can be garbage-collected)
+]
+ignore = ["E501"]
+
+[tool.ruff.lint.isort]
+known-first-party = ["db_module", "metrics_server", "rabbitmq_handler", "secret_manager",
+					"simple_logger_handler", "uvicorn_logger_config", "validator"]
+
+[tool.ruff.format]
+indent-style = "tab"
+
+[tool.ruff.lint.flake8-bugbear]
+extend-immutable-calls = [
+	"fastapi.Depends",
+	"fastapi.Query",
+	"fastapi.Header",
+	"fastapi.Body",
+	"fastapi.Security",
+]

requirements-dev.txt

@@ -0,0 +1 @@
+ruff==0.17.0

src/main.py

@@ -106,10 +106,10 @@ async def pull_notifications(
 		)
 	except (AMQPException, OSError) as e:
 		logger.error(f"[FastAPI] RabbitMQ unavailable for user_id={user_id}: {e}")
-		raise HTTPException(status_code=503, detail="Message broker unavailable")
+		raise HTTPException(status_code=503, detail="Message broker unavailable") from e
 	except RuntimeError as e:
 		logger.error(f"[FastAPI] Consumer not ready: {e}")
-		raise HTTPException(status_code=503, detail="Service not ready")
+		raise HTTPException(status_code=503, detail="Service not ready") from e
 
 	logger.info(f"[FastAPI] Retrieved {len(messages)} message(s) for user_id={user_id}")
 	return PullResponse(messages=messages, count=len(messages), has_more=len(messages) >= MAX_MESSAGES)

src/metrics_server.py

@@ -1,5 +1,5 @@
 from fastapi import FastAPI, Response
-from prometheus_client import generate_latest, CONTENT_TYPE_LATEST, Counter
+from prometheus_client import CONTENT_TYPE_LATEST, Counter, generate_latest
 
 metrics_api = FastAPI(title="Metrics Server", description="Prometheus metrics endpoint")
 

src/rabbitmq_handler.py

@@ -78,11 +78,11 @@ class RabbitMQConsumer:
 
 		- Only one fetch per user runs at a time; different users run concurrently.
 		- Messages are acked after the whole batch has been read, so an error mid-read
-		  puts the batch back on the queue and re-raises.
+		puts the batch back on the queue and re-raises.
 		- Undecodable messages are rejected without requeue (discarded).
 		- Returns an empty list if nothing is queued.
 		- Delivery is at-most-once towards the client: messages are acked before the
-		  HTTP response is sent.
+		HTTP response is sent.
 		"""
 
 		if self._closing: