import json
from datetime import datetime, timezone as dt_tz
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.permissions import AllowAny
from rest_framework.throttling import AnonRateThrottle
from rest_framework.parsers import BaseParser
from rest_framework.settings import api_settings
from tracker.models import Site
from tracker.services.ingest import ingest_batch

class PlainJSONParser(BaseParser):
    media_type = "text/plain"
    def parse(self, stream, *args, **kwargs):
        try:
            return json.loads(stream.read().decode("utf-8") or "{}")
        except (ValueError, UnicodeDecodeError):
            from rest_framework.exceptions import ParseError
            raise ParseError("invalid_json")   # DRF 对 parser 异常是 re-raise 不是包装，不自包就是 500

class CollectThrottle(AnonRateThrottle):
    scope = "collect"

    def get_rate(self):
        # SimpleRateThrottle.THROTTLE_RATES 在 import 时固化为类属性，
        # override_settings 改 DEFAULT_THROTTLE_RATES 对它不生效——改读实时 api_settings（DRF 收 setting_changed 会 reload）
        return api_settings.DEFAULT_THROTTLE_RATES[self.scope]

def _iso(dt):
    if isinstance(dt, str):
        s = dt.replace("Z", "+00:00")
        d = datetime.fromisoformat(s)
        return d if d.tzinfo else d.replace(tzinfo=dt_tz.utc)  # Django≥5 已删除 django.utils.timezone.utc
    return dt

class CollectBatchView(APIView):
    permission_classes = [AllowAny]
    parser_classes = [PlainJSONParser]
    throttle_classes = [CollectThrottle]
    authentication_classes = []

    def post(self, request):
        origin = request.headers.get("Origin") or request.headers.get("Referer") or ""
        if int(request.headers.get("Content-Length") or 0) > 262144:
            return self._deny(400, "payload_too_large")   # 应用层兜底（nginx 另设 client_max_body_size）
        site = self._match_site(request)
        if site is None or not site.is_active:
            return self._deny(403, "not_allowed")         # 三种拒绝统一 reason，防 site_id 枚举探测
        host = (origin.split("//")[-1].split("/")[0].split(":")[0].lower()
                if origin else "")
        if host and host not in [d.lower() for d in site.domains]:
            return self._deny(403, "not_allowed")
        if not host and not site.allow_no_origin:
            return self._deny(403, "not_allowed")
        payload = request.data if isinstance(request.data, dict) else {}
        for ev in payload.get("events") or []:
            if isinstance(ev, dict) and "occurred_at" in ev:
                try:
                    ev["occurred_at"] = _iso(ev["occurred_at"])
                except (ValueError, TypeError):
                    return self._deny(400, "invalid_occurred_at")
        if not payload.get("visitor_id") or not payload.get("session_id"):
            return self._deny(400, "invalid_payload")
        ip = self._client_ip(request)
        r = ingest_batch(site, payload, ip, request.headers.get("User-Agent", ""))
        resp = Response({"code": 200,
            "data": {"accepted": r["accepted"], "duplicated": r["duplicated"]},
            "message": "ok"})
        if origin:   # 成功分支回显 ACAO（SDK fetch 需读响应）
            resp["Access-Control-Allow-Origin"] = origin
            resp["Access-Control-Allow-Headers"] = "content-type"
        return resp

    def options(self, request):   # 预检兜底（SDK text/plain 简单请求通常不触发）
        origin = request.headers.get("Origin") or ""
        resp = Response(status=200)
        if origin:
            resp["Access-Control-Allow-Origin"] = origin
            resp["Access-Control-Allow-Methods"] = "POST, OPTIONS"
            resp["Access-Control-Allow-Headers"] = "content-type"
        return resp

    def _match_site(self, request):
        sid = (request.data or {}).get("site_id") if isinstance(request.data, dict) else None
        return Site.objects.filter(site_id=sid).first() if sid else None

    def _client_ip(self, request):
        """nginx 前置时取 X-Forwarded-For 最后一段（与 DRF NUM_PROXIES=1 一致；套 CDN 时按层数前移）。"""
        xff = request.META.get("HTTP_X_FORWARDED_FOR", "")
        ip = xff.split(",")[-1].strip() if xff else request.META.get("REMOTE_ADDR")
        # 归一 IPv4 映射地址（::ffff:1.2.3.4 → 1.2.3.4），防地理解析丢失
        if ip and ip.lower().startswith("::ffff:"):
            ip = ip[7:]
        return ip

    def _deny(self, code, reason):
        resp = Response({"code": code, "data": None, "message": reason}, status=code)
        origin = self.request.headers.get("Origin")
        if origin:   # 拒绝也要回 ACAO，否则浏览器读不到错误体、SDK 误判为网络错误走重试
            resp["Access-Control-Allow-Origin"] = origin
        return resp