package gateway

import (
	"context"
	"errors"
	"fmt"
	"log"
	"time"

	"github.com/wangjia/pay/internal/model"
	"github.com/wangjia/pay/internal/provider"
	"github.com/wangjia/pay/internal/store"
	"github.com/wangjia/pay/internal/util"

	"github.com/wangjia/pay/internal/accounts"
)

// webhook event 常量集中在 internal/gateway(Task 7 收敛业务方声明)。
const (
	EvtPaymentSucceeded     = "payment.succeeded"
	EvtSubscriptionCreated  = "subscription.created"
	EvtSubscriptionRenewed  = "subscription.renewed"
	EvtSubscriptionPastDue  = "subscription.past_due"
	EvtSubscriptionCanceled = "subscription.canceled"
	EvtChargebackReceived   = "chargeback.received"
)

type CreateSubscriptionInput struct {
	SKU       string
	Method    string
	BizSystem string
	BizRef    string
	ReturnURL string
}

type SubscriptionResult struct {
	SubID   string      `json:"sub_id"`
	OrderNo string      `json:"order_no"`
	Session SessionView `json:"session"`
}

// CreateSubscription 解析套餐权威金额 → 选 stripe 账户(须实现 SubscriptionProvider 且
// SupportsRecurring)→ 落 pending 首购 OrderV2 + Attempt → 返回订阅 Checkout redirect。
// 订阅在首期支付回调时诞生(见 onSubscriptionActivated)。
func (g *Gateway) CreateSubscription(ctx context.Context, in CreateSubscriptionInput) (*SubscriptionResult, error) {
	prov, err := g.providers.Get(in.Method)
	if err != nil {
		return nil, err
	}
	caps := prov.Capabilities()
	subProv, ok := prov.(provider.SubscriptionProvider)
	if !ok || !caps.SupportsRecurring {
		return nil, provider.ErrNotSupported
	}
	if len(caps.SettleCurrencies) == 0 {
		return nil, ErrNoSettleCurrency
	}
	currency := caps.SettleCurrencies[0]
	amount, subject, bizCode, err := g.products.Resolve(in.SKU, currency)
	if err != nil {
		return nil, err // ErrProductNotFound(含"该币种无价")
	}
	outTradeNo := util.NewOutTradeNo("pay")
	acct, err := g.picker.Pick(in.Method, g.region, accounts.PickHint{OutTradeNo: outTradeNo, AmountMinor: amount})
	if err != nil {
		if errors.Is(err, accounts.ErrNoAccount) {
			return nil, ErrNoAccount
		}
		return nil, err
	}
	// SubID 确定性派生自 out_trade_no(与 onSubscriptionActivated 一致,消除双号)。
	subID := "SUB-" + outTradeNo
	sess, err := subProv.CreateSubscriptionCheckout(ctx, provider.CreateRequest{
		OutTradeNo: outTradeNo, Subject: subject, AmountMinor: amount, Currency: currency,
		Account: acct, ReturnURL: in.ReturnURL, Metadata: map[string]string{"pay_sub_id": subID},
	})
	if err != nil {
		return nil, fmt.Errorf("gateway.CreateSubscription: %w", err)
	}
	order := &model.OrderV2{
		OutTradeNo: outTradeNo, BizSystem: in.BizSystem, BizRef: in.BizRef, BizCode: bizCode,
		Subject: subject, AmountMinor: amount, Currency: currency, Status: model.OrderPendingV2,
	}
	if err := g.orders.CreateOrder(order); err != nil {
		return nil, err
	}
	att := &model.Attempt{
		OutTradeNo: outTradeNo, Channel: in.Method, AccountID: acct.AccountID, Provider: in.Method,
		ProviderRef: sess.ProviderRef, RenderType: string(sess.RenderType),
		AmountMinor: amount, Currency: currency, Status: model.AttemptPending, ExpiresAt: sess.ExpiresAt,
	}
	if err := g.orders.CreateAttempt(att); err != nil {
		return nil, err
	}
	return &SubscriptionResult{
		SubID: subID, OrderNo: outTradeNo,
		Session: SessionView{RenderType: string(sess.RenderType), Payload: sess.Payload, ExpiresAt: sess.ExpiresAt},
	}, nil
}

// onSubscriptionActivated 幂等诞生订阅 + 入队 subscription.created。首期支付回调触发。
// created 事件走首购 order 的 out_trade_no + event_type=subscription.created(唯一键天然不撞 payment.succeeded)。
func (g *Gateway) onSubscriptionActivated(ctx context.Context, ev *provider.PaidEvent) error {
	att, err := g.orders.AttemptByProviderRef(ev.ProviderRef)
	if err != nil {
		return nil // 首期会话未落库(不该发生);交由 Settle 侧日志,订阅侧静默
	}
	o, err := g.orders.GetOrder(att.OutTradeNo)
	if err != nil {
		return err
	}
	if !o.Status.Settled() {
		// 纵深防御:HandleCallback 的门(res==Processed/Duplicate)已挡住未结算订单,
		// 这里再核一遍订单状态,防止未来调用点绕过门直接调用本函数。
		log.Printf("[subscription] onSubscriptionActivated 订单未结算 out_trade_no=%s status=%s,拒绝激活", o.OutTradeNo, o.Status)
		return nil
	}
	subID := "SUB-" + att.OutTradeNo // 与 CreateSubscription 同式派生 → 重投算出同一 SubID,Create 幂等
	created, err := g.subs.Create(&model.Subscription{
		SubID: subID, OutTradeNo: o.OutTradeNo, BizSystem: o.BizSystem, BizRef: o.BizRef, BizCode: o.BizCode,
		Channel: att.Channel, ProviderSubRef: ev.SubscriptionRef, RecurringKind: provider.RecurringKindGatewayScheduled,
		AmountMinor: o.AmountMinor, Currency: o.Currency, Status: model.SubActive,
	})
	if err != nil {
		return err
	}
	if !created || o.BizSystem == "" {
		return nil // 已诞生过(重投)/ 独立收款无业务方回调
	}
	return g.webhook.Enqueue(o.OutTradeNo, o.BizSystem, EvtSubscriptionCreated, "", map[string]any{
		"event_type": EvtSubscriptionCreated, "out_trade_no": o.OutTradeNo, "sub_id": subID,
		"biz_system": o.BizSystem, "biz_ref": o.BizRef, "product_biz_code": o.BizCode,
		"amount_minor": o.AmountMinor, "currency": o.Currency, "channel": att.Channel,
		"created_at": time.Now().Format(time.RFC3339),
	})
}

// SubscriptionView — GET /api/v2/subscriptions/:sub_id 返回视图(状态 + 续费锚点)。
type SubscriptionView struct {
	SubID            string     `json:"sub_id"`
	Status           string     `json:"status"`
	CurrentPeriodEnd *time.Time `json:"current_period_end,omitempty"`
	CanceledAt       *time.Time `json:"canceled_at,omitempty"`
}

func (g *Gateway) GetSubscription(subID string) (*SubscriptionView, error) {
	sub, err := g.subs.GetBySubID(subID)
	if err != nil {
		return nil, err // store.ErrSubNotFound
	}
	return &SubscriptionView{
		SubID: sub.SubID, Status: string(sub.Status),
		CurrentPeriodEnd: sub.CurrentPeriodEnd, CanceledAt: sub.CanceledAt,
	}, nil
}

// CancelSubscription 主动取消(POST /api/v2/subscriptions/:sub_id/cancel):查订阅 → 已终态则
// 幂等 no-op(不再打渠道,避免重复取消命中渠道 400)→ 渠道侧取消 → 本地翻 canceled + 入队
// subscription.canceled。Stripe 随后异步发 customer.subscription.deleted,入站处理器
// (settleSubscriptionCanceled)再次调用同一 finalizeCanceled,两路收敛同一终态、天然幂等。
func (g *Gateway) CancelSubscription(ctx context.Context, subID string) error {
	sub, err := g.subs.GetBySubID(subID)
	if err != nil {
		return err // store.ErrSubNotFound
	}
	if sub.Status == model.SubCanceled {
		return nil // 已取消(重复调用/webhook 已先到):幂等 no-op,不再打渠道
	}
	prov, err := g.providers.Get(sub.Channel)
	if err != nil {
		return err
	}
	if sp, ok := prov.(provider.SubscriptionProvider); ok {
		if err := sp.CancelSubscription(ctx, sub.ProviderSubRef); err != nil {
			return err
		}
	}
	return g.finalizeCanceled(sub)
}

// settleSubscriptionCanceled 处理入站 customer.subscription.deleted:反查订阅 → finalizeCanceled。
// 未知 provider_sub_ref(订阅未诞生/已清理)忽略,不报错(与 settleRenewal 同惯例)。
func (g *Gateway) settleSubscriptionCanceled(ctx context.Context, method string, ev *provider.PaidEvent) (SettleResult, error) {
	sub, err := g.subs.GetByProviderRef(method, ev.SubscriptionRef)
	if err != nil {
		if errors.Is(err, store.ErrSubNotFound) {
			return SettleIgnored, nil
		}
		return SettleFailed, err
	}
	if err := g.finalizeCanceled(sub); err != nil {
		return SettleFailed, err
	}
	return SettleProcessed, nil
}

// finalizeCanceled 是取消的唯一落地点(主动取消 API + 入站 webhook 两路收敛于此):
// MarkCanceled 幂等翻转 canceled;仅首次真正翻转(flipped)且有业务方(BizSystem 非空)
// 才入队 subscription.canceled——重投/独立收款不重复发。
//
// outbox 键取真实首购单号 sub.OutTradeNo(不用合成后缀键):该单已 paid,Notifier 投递门禁
// (orderPaid)天然放行;event_type=subscription.canceled 与该单已有的 payment.succeeded /
// subscription.created 行不同 event_type,唯一键 (out_trade_no,event_type,refund_id) 不撞。
// canceled 每订阅只发生一次,不存在"同订阅多次 canceled 被吞"的问题(不同于 past_due)。
func (g *Gateway) finalizeCanceled(sub *model.Subscription) error {
	flipped, err := g.subs.MarkCanceled(sub.SubID)
	if err != nil {
		return err
	}
	if !flipped || sub.BizSystem == "" {
		return nil // 已取消(重投)/ 独立收款无业务方回调
	}
	return g.webhook.Enqueue(sub.OutTradeNo, sub.BizSystem, EvtSubscriptionCanceled, "", map[string]any{
		"event_type": EvtSubscriptionCanceled, "out_trade_no": sub.OutTradeNo, "sub_id": sub.SubID,
		"biz_system": sub.BizSystem, "biz_ref": sub.BizRef, "product_biz_code": sub.BizCode,
		"canceled_at": time.Now().Format(time.RFC3339),
	})
}

// markSubscriptionPastDue 处理入站 invoice.payment_failed:active→past_due(MarkPastDue 只在
// 当前 active 时翻转,已 past_due/已 canceled 不动),入队 subscription.past_due 供业务方提醒
// 用户换卡。下期 invoice.paid 成功由 settleRenewal 的 Activate 自动恢复 active。
//
// outbox 键取真实首购单号 sub.OutTradeNo(理由同 finalizeCanceled):Task5 最小可行接受
// "同订阅多次 past_due 只报首次"(第二次失败的行撞 (out_trade_no,event_type) 唯一键、
// EnqueueDelivery 幂等 no-op),Task 7 视需要再引入合成键 + Notifier 门禁旁路。
func (g *Gateway) markSubscriptionPastDue(ctx context.Context, method string, ev *provider.PaidEvent) (SettleResult, error) {
	sub, err := g.subs.GetByProviderRef(method, ev.SubscriptionRef)
	if err != nil {
		if errors.Is(err, store.ErrSubNotFound) {
			return SettleIgnored, nil
		}
		return SettleFailed, err
	}
	flipped, err := g.subs.MarkPastDue(sub.Channel, sub.ProviderSubRef)
	if err != nil {
		return SettleFailed, err
	}
	if !flipped || sub.BizSystem == "" {
		return SettleDuplicate, nil
	}
	if err := g.webhook.Enqueue(sub.OutTradeNo, sub.BizSystem, EvtSubscriptionPastDue, "", map[string]any{
		"event_type": EvtSubscriptionPastDue, "out_trade_no": sub.OutTradeNo, "sub_id": sub.SubID,
		"biz_system": sub.BizSystem, "biz_ref": sub.BizRef, "product_biz_code": sub.BizCode,
		"failed_at": time.Now().Format(time.RFC3339),
	}); err != nil {
		return SettleFailed, err
	}
	return SettleProcessed, nil
}