"""套餐与计费 API（批次 C1）。

- GET  /api/v1/billing/plans/          套餐列表（官网价格页数据源）
- GET  /api/v1/billing/subscription/   我的套餐 + 用量
- POST /api/v1/billing/subscribe/      变更套餐（真实支付接入后由回调驱动）
"""

from asgiref.sync import sync_to_async
from adrf.decorators import api_view
from rest_framework import status
from rest_framework.decorators import authentication_classes, permission_classes
from rest_framework.permissions import AllowAny
from rest_framework.response import Response
from rest_framework.exceptions import ValidationError

from apps.core.viewset import resolve_tenant
from .models import Plan, Subscription, upgrade, get_subscription, seed_plans
from . import quota as billing_quota


async def _tenant(request):
    code = request.META.get("HTTP_X_TENANT_ID", "")
    tenant = await sync_to_async(resolve_tenant)(code)
    if tenant is None:
        raise ValidationError({"tenant": "无法识别租户"})
    return tenant


@api_view(["GET"])
@authentication_classes([])
@permission_classes([AllowAny])
async def plan_list(request):
    """套餐列表（价格 + 功能对比）。公开：官网价格页/登录页都需要。"""

    def _load():
        seed_plans()
        return list(Plan.objects.filter(is_active=True).order_by("sort_order", "code"))

    plans = await sync_to_async(_load)()
    return Response([
        {
            "code": p.code,
            "name": p.name,
            "price_monthly": str(p.price_monthly),
            "description": p.description,
            "limits": p.limits,
        }
        for p in plans
    ])


@api_view(["GET"])
async def my_subscription(request):
    """我的套餐状态 + 各项用量（升级引导弹窗数据源）。"""
    tenant = await _tenant(request)
    snap = await sync_to_async(billing_quota.usage_snapshot)(tenant)
    return Response(snap)


@api_view(["POST"])
async def change_plan(request):
    """变更套餐：POST {plan_code, months?}。

    真实支付接入前：直接切换（演示/内部开通用）；接入支付后应改为
    "创建订单 → 支付回调 → upgrade"，此接口仅保留给管理员。
    """
    tenant = await _tenant(request)
    payload = request.data or {}
    plan_code = (payload.get("plan_code") or "").strip()
    if not plan_code:
        raise ValidationError({"detail": "plan_code 必填"})
    months = int(payload.get("months") or 1)

    def _do():
        sub = upgrade(tenant, plan_code, months=months)
        return sub

    try:
        sub = await sync_to_async(_do)()
    except ValueError as exc:
        return Response({"detail": str(exc)}, status=status.HTTP_400_BAD_REQUEST)

    return Response({
        "ok": True,
        "plan_code": sub.plan.code,
        "plan_name": sub.plan.name,
        "status": sub.status,
        "period_end": sub.period_end.isoformat() if sub.period_end else None,
    })


@api_view(["GET"])
async def quota_check(request):
    """预检某配额项：?kind=products（前端按钮置灰/拦截提示用）。

    语义是"还能不能再加一个"：delta=1，因此 used 已达上限即返回 403。
    """
    tenant = await _tenant(request)
    kind = request.query_params.get("kind") or ""
    if not kind:
        raise ValidationError({"detail": "kind 必填（products/bills_monthly/ai_parse_order/...）"})

    def _check():
        return billing_quota.check_and_count(tenant, kind, delta=1)

    try:
        out = await sync_to_async(_check)()
    except billing_quota.QuotaExceeded as exc:
        return Response(exc.as_dict(), status=status.HTTP_403_FORBIDDEN)
    return Response(out)