Add initial versionHEADmain

1 files changed, 67 insertions, 0 deletions

diff --git a/src/nvd/rate_limiter.py b/src/nvd/rate_limiter.py
new file mode 100644
index 0000000..be0fddf
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+++ b/src/nvd/rate_limiter.py
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+"""Async rate limiter for NVD API requests."""
+
+import asyncio
+import time
+from collections import deque
+from typing import Deque
+
+
+class RateLimiter:
+    """Sliding window rate limiter for async operations.
+
+    NVD API rate limits:
+    - Without API key: 5 requests per 30 seconds
+    - With API key: 50 requests per 30 seconds
+    """
+
+    def __init__(self, max_requests: int = 5, window_seconds: int = 30) -> None:
+        """Initialize rate limiter.
+
+        Args:
+            max_requests: Maximum number of requests allowed in the time window
+            window_seconds: Time window in seconds
+        """
+        self.max_requests = max_requests
+        self.window_seconds = window_seconds
+        self._requests: Deque[float] = deque()
+        self._lock = asyncio.Lock()
+
+    async def acquire(self) -> None:
+        """Acquire permission to make a request, waiting if necessary."""
+        async with self._lock:
+            now = time.time()
+
+            # Remove requests outside the current window
+            while self._requests and self._requests[0] <= now - self.window_seconds:
+                self._requests.popleft()
+
+            # If at limit, wait until oldest request expires
+            if len(self._requests) >= self.max_requests:
+                sleep_time = self._requests[0] + self.window_seconds - now
+                if sleep_time > 0:
+                    await asyncio.sleep(sleep_time)
+                    # Recursively try again after waiting
+                    return await self.acquire()
+
+            # Record this request
+            self._requests.append(now)
+
+    def configure(self, has_api_key: bool) -> None:
+        """Configure rate limiter based on whether an API key is present.
+
+        Args:
+            has_api_key: Whether an API key is being used
+        """
+        if has_api_key:
+            self.max_requests = 50
+        else:
+            self.max_requests = 5
+
+    async def __aenter__(self) -> "RateLimiter":
+        """Async context manager entry."""
+        await self.acquire()
+        return self
+
+    async def __aexit__(self, *args: object) -> None:
+        """Async context manager exit."""
+        pass