# utils/rate_limit.py — 基于 Redis 缓存的频控与失败计数（同步/异步兼容）
from django.core.cache import caches

default_cache = caches['default']


def get_client_ip(request) -> str:
    """
    安全提取客户端真实 IP：优先取反向代理注入的 X-Real-IP，杜绝伪造 X-Forwarded-For 绕过限流
    """
    if not request:
        return ''
    real_ip = request.META.get('HTTP_X_REAL_IP')
    if real_ip:
        return real_ip.strip()
    fwd = request.META.get('HTTP_X_FORWARDED_FOR')
    if fwd:
        return fwd.split(',')[0].strip()
    return request.META.get('REMOTE_ADDR', '').strip()


def _client_key(scope: str, identifier: str) -> str:
    return f'rl_{scope}_{identifier}'


def check_rate_limit(scope: str, identifier: str, limit: int, window_seconds: int) -> bool:
    """
    固定窗口频控：同 identifier 在 window_seconds 秒内允许最多 limit 次请求。
    返回 True 表示放行，False 表示已被限流。
    """
    if not identifier:
        return True
    key = _client_key(scope, identifier)
    try:
        count = default_cache.get(key)
    except Exception:
        # Redis 异常时保持放行，避免误伤业务
        return True

    if count is None:
        try:
            default_cache.set(key, 1, timeout=window_seconds)
        except Exception:
            return True
        return True

    try:
        count = int(count)
    except (TypeError, ValueError):
        count = 0

    if count >= limit:
        return False

    try:
        default_cache.set(key, count + 1, timeout=window_seconds)
    except Exception:
        return True
    return True


def record_failure(scope: str, identifier: str, max_failures: int = 5, window_seconds: int = 300) -> int:
    """
    记录一次失败并返回当前累计失败次数。
    """
    if not identifier:
        return 0
    key = f'fail_{scope}_{identifier}'
    try:
        count = default_cache.get(key)
        new_count = (int(count) + 1) if count is not None else 1
        default_cache.set(key, new_count, timeout=window_seconds)
        return new_count
    except Exception:
        return 0


def get_failure_count(scope: str, identifier: str) -> int:
    """
    获取当前失败次数
    """
    if not identifier:
        return 0
    key = f'fail_{scope}_{identifier}'
    try:
        count = default_cache.get(key)
        return int(count) if count is not None else 0
    except Exception:
        return 0


def reset_failures(scope: str, identifier: str):
    """
    重置失败计数
    """
    if not identifier:
        return
    key = f'fail_{scope}_{identifier}'
    try:
        default_cache.delete(key)
    except Exception:
        pass