"""历史来源分类全量重算（幂等可重复）。

规则引擎升级（constants.ATTRIBUTION_RULE_VERSION bump）后执行：
    python manage.py recompute_attribution            # 全部站点
    python manage.py recompute_attribution --site site_xxx

数据源约束：重算只能用"落库时保住的信号"——
  - 访客首触：最早 page_view 的 properties.referrer/utm（无则档案字段兜底，
    referrer_domain 合成 URL 后搜索词已丢失，诚实降级）+ first_landing_path；UA 未存档 → 空。
  - 会话入口：referrer_domain 合成 URL + utm + landing_path。
逐条 upsert（first_touch 键 site+visitor+scope；session_entry 键 site+session+scope），
跑两遍计数不变。
"""
from django.core.management.base import BaseCommand

from tracker import constants as C
from tracker.models import Event, Site, SourceClassification, VisitSession, Visitor
from tracker.services.attribution import classify


def _first_touch_signals(visitor):
    """最早一条 page_view 的原始信号优先；旧数据无事件属性时回落访客档案字段。"""
    ev = (Event.objects.filter(visitor=visitor, event_name="page_view")
          .order_by("occurred_at", "pk").first())
    props = (ev.properties or {}) if ev else {}
    referrer = props.get("referrer") if isinstance(props.get("referrer"), str) else ""
    domain = props.get("referrer_domain") or visitor.first_referrer_domain
    if not referrer and domain:
        referrer = f"https://{str(domain).strip().strip('/')}"
    utm = props.get("utm") if isinstance(props.get("utm"), dict) else None
    return referrer, (utm or visitor.first_utm or {}), visitor.first_landing_path


def _upsert(site, visitor, session, scope, result):
    vals = {"channel": (result["channel"] or "")[:32],
            "platform": (result["platform"] or "")[:64],
            "variant": (result["variant"] or "")[:64],
            "search_term": (result["search_term"] or "")[:200],
            "evidence_kind": (result["evidence_kind"] or "")[:32],
            "resolution": (result["resolution"] or "")[:16],
            "detail": result["detail"] or {}, "session": session,
            "rule_version": C.ATTRIBUTION_RULE_VERSION}   # 重算即升到当前规则版本
    if session is None:
        SourceClassification.objects.update_or_create(
            site=site, visitor=visitor, scope=scope, defaults=vals)
    else:
        SourceClassification.objects.update_or_create(
            site=site, session=session, scope=scope,
            defaults={**vals, "visitor": visitor})


class Command(BaseCommand):
    help = "按当前规则版本全量重算来源分类（first_touch + session_entry，幂等）"

    def add_arguments(self, parser):
        parser.add_argument("--site", default=None,
                            help="只重算指定 site_id（缺省全部站点）")

    def handle(self, *args, **opts):
        sites = Site.objects.all()
        if opts["site"]:
            sites = sites.filter(site_id=opts["site"])
            if not sites.exists():
                self.stdout.write(self.style.WARNING(
                    f"site not found: {opts['site']}"))
                return
        v_total = s_total = 0
        for site in sites:
            domains = site.domains or []
            for visitor in Visitor.objects.filter(site=site).only("pk", "first_referrer_domain",
                                                                  "first_utm", "first_landing_path"):
                referrer, utm, landing = _first_touch_signals(visitor)
                _upsert(site, visitor, None, "first_touch",
                        classify(referrer_url=referrer, utm=utm,
                                 landing_path=landing or "",
                                 internal_domains=domains))
                v_total += 1
            for sess in VisitSession.objects.filter(site=site).select_related("visitor"):
                referrer = f"https://{sess.referrer_domain.strip().strip('/')}" \
                    if sess.referrer_domain else ""
                _upsert(site, sess.visitor, sess, "session_entry",
                        classify(referrer_url=referrer, utm=sess.utm or {},
                                 landing_path=sess.landing_path or "",
                                 internal_domains=domains))
                s_total += 1
        self.stdout.write(
            f"recomputed attribution: {v_total} first_touch, {s_total} session_entry "
            f"(rule version {C.ATTRIBUTION_RULE_VERSION})")