from datetime import datetime, time, timedelta
from django.db.models import Count, Sum
from django.utils import timezone
from rest_framework.views import APIView
from rest_framework.response import Response
from tracker.api.envelope import EnvelopeMixin, ok
from tracker.models import DailyStat, Event, Site, VisitSession, Visitor
from tracker.services.stats import daily_counts

METRICS = ("pv", "uv", "sessions", "new_visitors")


def _day_bounds(date):
    """上海自然日窗口，与 daily_counts 同款 make_aware。"""
    start = timezone.make_aware(datetime.combine(date, time.min))
    return start, start + timedelta(days=1)


class OverviewView(EnvelopeMixin, APIView):
    def get(self, request):
        site = None
        sid = request.query_params.get("site")
        if sid:
            site = Site.objects.filter(site_id=sid).first()
            if not site:
                return Response({"code": 404, "data": None,
                                 "message": "site_not_found"}, status=404)
        today = timezone.localdate()
        counts = daily_counts(site, today)          # 与 refresh_daily 共享口径（Task8 审查结论）
        counts["active_now"] = self._active_now(site)
        return ok({"today": counts,
                   "trend": self._trend(site, today, counts),
                   "sources": self._today_sources(site, today),
                   "top_pages": self._today_pages(site, today)})

    @staticmethod
    def _active_now(site):
        # 5 分钟内有行为的访客（last_seen_at 有 site,-last_seen_at 索引；不用无索引的 received_at）
        q = Visitor.objects.filter(is_bot=False,
                                   last_seen_at__gt=timezone.now() - timedelta(minutes=5))
        if site is not None:
            q = q.filter(site=site)
        return q.count()

    def _trend(self, site, today, today_counts):
        """DailyStat 近 30 天（缺日补零；今天一位用 daily_counts 实时值覆盖——聚合作业未跑也不缺当日）。"""
        days = 30
        start = today - timedelta(days=days - 1)
        qs = DailyStat.objects.filter(date__gte=start, date__lte=today)
        if site is not None:
            qs = qs.filter(site=site)
        rows = {r["date"]: r for r in qs.values("date").annotate(
            pv=Sum("pv"), uv=Sum("uv"), sessions=Sum("sessions"),
            new_visitors=Sum("new_visitors"))}
        out = []
        for i in range(days):
            date = start + timedelta(days=i)
            if date == today:
                out.append({"date": date.isoformat(),
                            **{k: today_counts[k] for k in METRICS}})
            else:
                r = rows.get(date, {})
                out.append({"date": date.isoformat(),
                            **{k: r.get(k, 0) for k in METRICS}})
        return out

    def _today_sources(self, site, today):
        start, end = _day_bounds(today)
        q = VisitSession.objects.filter(visitor__is_bot=False,
                                        started_at__gte=start, started_at__lt=end)
        if site is not None:
            q = q.filter(site=site)
        return [{"source": r["referrer_domain"] or "直接访问", "sessions": r["n"]}
                for r in q.values("referrer_domain")
                         .annotate(n=Count("id"))
                         .order_by("-n", "referrer_domain")[:8]]   # 平局时次序跨请求稳定

    def _today_pages(self, site, today):
        start, end = _day_bounds(today)
        q = Event.objects.filter(is_bot=False, event_name="page_view",
                                 occurred_at__gte=start, occurred_at__lt=end)
        if site is not None:
            q = q.filter(site=site)
        return [{"path": r["path"], "pv": r["n"]}
                for r in q.values("path")
                         .annotate(n=Count("id"))
                         .order_by("-n", "path")[:8]]   # 平局时次序跨请求稳定