feat: add RateLimiter utility class

Author: LifeJiggy

src/gradient/_utils/__init__.py

@@ -29,6 +29,7 @@
     get_required_header as get_required_header,
     maybe_coerce_boolean as maybe_coerce_boolean,
     maybe_coerce_integer as maybe_coerce_integer,
+    RateLimiter as RateLimiter,
 )
 from ._compat import (
     get_args as get_args,

src/gradient/_utils/_utils.py

@@ -419,3 +419,48 @@ def json_safe(data: object) -> object:
         return data.isoformat()
 
     return data
+
+
+# Rate Limiting Classes
+class RateLimiter:
+    """Simple token bucket rate limiter."""
+
+    def __init__(self, requests_per_minute: int = 60) -> None:
+        """Initialize rate limiter.
+
+        Args:
+            requests_per_minute: Maximum requests allowed per minute
+        """
+        self.requests_per_minute: int = requests_per_minute
+        self.tokens: float = float(requests_per_minute)
+        self.last_refill: float = self._now()
+        self.refill_rate: float = requests_per_minute / 60.0  # tokens per second
+
+    def _now(self) -> float:
+        """Get current time in seconds."""
+        import time
+        return time.time()
+
+    def _refill(self) -> None:
+        """Refill tokens based on elapsed time."""
+        now = self._now()
+        elapsed = now - self.last_refill
+        self.tokens = min(self.requests_per_minute, self.tokens + elapsed * self.refill_rate)
+        self.last_refill = now
+
+    def acquire(self, tokens: int = 1) -> bool:
+        """Try to acquire tokens. Returns True if successful."""
+        self._refill()
+        if self.tokens >= tokens:
+            self.tokens -= tokens
+            return True
+        return False
+
+    def wait_time(self, tokens: int = 1) -> float:
+        """Get seconds to wait for tokens to be available."""
+        self._refill()
+        if self.tokens >= tokens:
+            return 0.0
+
+        needed = tokens - self.tokens
+        return needed / self.refill_rate

tests/test_rate_limiter.py

@@ -0,0 +1,56 @@
+"""Tests for rate limiting functionality."""
+
+import time
+import pytest
+from gradient._utils import RateLimiter
+
+
+class TestRateLimiter:
+    """Test rate limiting functionality."""
+
+    def test_rate_limiter_basic(self):
+        """Test basic rate limiter operations."""
+        limiter = RateLimiter(requests_per_minute=10)
+
+        # Should allow initial requests
+        assert limiter.acquire() is True
+        assert limiter.acquire() is True
+
+        # Should deny when tokens exhausted
+        limiter.tokens = 0  # Force exhaustion
+        assert limiter.acquire() is False
+
+    def test_rate_limiter_wait_time(self):
+        """Test wait time calculation."""
+        limiter = RateLimiter(requests_per_minute=60)  # 1 request per second
+
+        # Exhaust tokens
+        limiter.tokens = 0
+
+        # Should calculate correct wait time
+        wait_time = limiter.wait_time()
+        assert wait_time > 0
+        assert wait_time <= 1.0  # Should not exceed 1 second
+
+    def test_rate_limiter_refill(self):
+        """Test token refill over time."""
+        limiter = RateLimiter(requests_per_minute=60)  # 1 token per second
+
+        # Exhaust tokens
+        limiter.tokens = 0
+        start_time = limiter._now()
+
+        # Wait for refill
+        time.sleep(0.1)
+
+        # Should have refilled some tokens
+        limiter._refill()
+        assert limiter.tokens > 0
+
+    def test_rate_limiter_custom_rate(self):
+        """Test custom rate limits."""
+        limiter = RateLimiter(requests_per_minute=120)  # 2 requests per second
+
+        # Should have double the tokens of default
+        assert limiter.requests_per_minute == 120
+        assert limiter.refill_rate == 2.0