Initial commit: fastapi-traffic rate limiting library

- Core rate limiting with multiple algorithms (sliding window, token bucket, etc.)
- SQLite and memory backends
- Decorator and dependency injection patterns
- Middleware support
- Example usage files

fastapi_traffic/core/config.py

@@ -0,0 +1,81 @@
+"""Configuration for rate limiting."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import TYPE_CHECKING, Any, Callable
+
+from fastapi_traffic.core.algorithms import Algorithm
+
+if TYPE_CHECKING:
+    from starlette.requests import Request
+
+    from fastapi_traffic.backends.base import Backend
+
+
+KeyExtractor = Callable[["Request"], str]
+
+
+def default_key_extractor(request: Request) -> str:
+    """Extract client IP as the default rate limit key."""
+    forwarded = request.headers.get("X-Forwarded-For")
+    if forwarded:
+        return forwarded.split(",")[0].strip()
+
+    real_ip = request.headers.get("X-Real-IP")
+    if real_ip:
+        return real_ip
+
+    if request.client:
+        return request.client.host
+
+    return "unknown"
+
+
+@dataclass(slots=True)
+class RateLimitConfig:
+    """Configuration for a rate limit rule."""
+
+    limit: int
+    window_size: float = 60.0
+    algorithm: Algorithm = Algorithm.SLIDING_WINDOW_COUNTER
+    key_prefix: str = "ratelimit"
+    key_extractor: KeyExtractor = field(default=default_key_extractor)
+    burst_size: int | None = None
+    include_headers: bool = True
+    error_message: str = "Rate limit exceeded"
+    status_code: int = 429
+    skip_on_error: bool = False
+    cost: int = 1
+    exempt_when: Callable[[Request], bool] | None = None
+    on_blocked: Callable[[Request, Any], Any] | None = None
+
+    def __post_init__(self) -> None:
+        if self.limit <= 0:
+            msg = "limit must be positive"
+            raise ValueError(msg)
+        if self.window_size <= 0:
+            msg = "window_size must be positive"
+            raise ValueError(msg)
+        if self.cost <= 0:
+            msg = "cost must be positive"
+            raise ValueError(msg)
+
+
+@dataclass(slots=True)
+class GlobalConfig:
+    """Global configuration for the rate limiter."""
+
+    backend: Backend | None = None
+    enabled: bool = True
+    default_limit: int = 100
+    default_window_size: float = 60.0
+    default_algorithm: Algorithm = Algorithm.SLIDING_WINDOW_COUNTER
+    key_prefix: str = "fastapi_traffic"
+    include_headers: bool = True
+    error_message: str = "Rate limit exceeded. Please try again later."
+    status_code: int = 429
+    skip_on_error: bool = False
+    exempt_ips: set[str] = field(default_factory=set)
+    exempt_paths: set[str] = field(default_factory=set)
+    headers_prefix: str = "X-RateLimit"