import hashlib
import time
from django.conf import settings
from django.core.cache import cache
from django.http import JsonResponse


class RateLimitMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        if not getattr(settings, "RATE_LIMIT_ENABLE", False):
            return self.get_response(request)

        path = request.path or ""
        rate_limit_paths = getattr(settings, "RATE_LIMIT_PATHS", ["/api/"])
        if not any(path.startswith(prefix) for prefix in rate_limit_paths):
            return self.get_response(request)

        window = int(getattr(settings, "RATE_LIMIT_WINDOW_SECONDS", 60))
        max_requests = int(getattr(settings, "RATE_LIMIT_REQUESTS", 120))
        now = int(time.time())
        window_key = now // max(window, 1)

        ident = request.META.get("HTTP_X_FORWARDED_FOR", "").split(",")[0].strip()
        if not ident:
            ident = request.META.get("REMOTE_ADDR", "unknown")
        cache_key = f"rate:{ident}:{window_key}"

        try:
            current = cache.incr(cache_key)
        except ValueError:
            cache.add(cache_key, 1, timeout=window)
            current = 1

        if current > max_requests:
            return JsonResponse(
                {"message": "请求过于频繁，请稍后再试", "success": False},
                status=429,
            )

        return self.get_response(request)


class ETagMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        response = self.get_response(request)

        if request.method not in {"GET", "HEAD"}:
            return response
        if response.status_code != 200:
            return response
        if response.has_header("ETag"):
            return response

        content_type = response.get("Content-Type", "")
        if "application/json" not in content_type:
            return response

        content = getattr(response, "content", b"") or b""
        max_bytes = int(getattr(settings, "ETAG_MAX_BYTES", 2 * 1024 * 1024))
        if len(content) > max_bytes:
            return response

        etag = hashlib.sha256(content).hexdigest()
        etag_value = f'W/"{etag}"'
        response["ETag"] = etag_value
        response["Cache-Control"] = "private, max-age=0"

        if_none_match = request.META.get("HTTP_IF_NONE_MATCH")
        if if_none_match and if_none_match == etag_value:
            response.status_code = 304
            response.content = b""

        return response