Updates

backend/app/core/rate_limit.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import time
+from collections import deque
+from dataclasses import dataclass
+from threading import Lock
+
+from fastapi import HTTPException, Request, status
+
+
+@dataclass
+class SlidingWindowRateLimiter:
+    limit: int
+    window_seconds: int
+
+    def __post_init__(self) -> None:
+        self._events: dict[str, deque[float]] = {}
+        self._lock = Lock()
+
+    def hit(self, key: str) -> None:
+        now = time.time()
+        floor = now - self.window_seconds
+
+        with self._lock:
+            bucket = self._events.setdefault(key, deque())
+            while bucket and bucket[0] <= floor:
+                bucket.popleft()
+            if len(bucket) >= self.limit:
+                raise HTTPException(
+                    status_code=status.HTTP_429_TOO_MANY_REQUESTS,
+                    detail="Too many requests. Please try again later.",
+                )
+            bucket.append(now)
+
+
+def request_client_key(request: Request, *, suffix: str = "") -> str:
+    forwarded_for = request.headers.get("x-forwarded-for", "")
+    client_ip = forwarded_for.split(",", 1)[0].strip() if forwarded_for else (request.client.host if request.client else "unknown")
+    return f"{client_ip}:{suffix}" if suffix else client_ip