"""Configuration for rate limiting."""

from __future__ import annotations

from collections.abc import Callable
from dataclasses import dataclass, field
from typing import TYPE_CHECKING, Any

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"