package service

import (
	"context"
	"log/slog"
	"sync"
	"time"

	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/global"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqldao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/mysqlmodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/redisdao"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/redismodel"
	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/wechat"
)

const (
	// virtualRefundConfirmGraceSeconds 退款申请的宽限期：只处理停留超过该时长的「申请退款中」订单，
	// 给退款推送留出处理时间，避免与推送路径抢跑。
	virtualRefundConfirmGraceSeconds int64 = 10 * 60
	// virtualRefundConfirmBatchSize 单轮最多扫描的候选订单数。
	virtualRefundConfirmBatchSize = 100
	// virtualRefundConfirmWorkers 单轮并发反查的 worker 数（query_order 为 HTTP 调用，串行会在积压时撞上超时）。
	virtualRefundConfirmWorkers = 5
	// virtualRefundConfirmRecheckTTL 单个订单的查单频率下限：命中「已核对」标记则跳过本轮，
	// 把单个订单的微信接口调用频率压到每 TTL 一次（退款为人工审核，长时间停留在 6 属正常）。
	virtualRefundConfirmRecheckTTL = 10 * time.Minute
	// virtualRefundConfirmStuckSeconds 停留超过该时长仍未见微信侧退款 -> Error 告警交人工介入。
	virtualRefundConfirmStuckSeconds int64 = 24 * 60 * 60
	// virtualRefundConfirmStuckAlertTTL 「长期未完成」告警去重 TTL，避免每分钟刷屏。
	virtualRefundConfirmStuckAlertTTL = 6 * time.Hour
	// virtualRefundConfirmLockTTL 单轮任务的分布式锁 TTL，必须大于单轮最大耗时，否则锁提前过期会让多实例并发执行。
	virtualRefundConfirmLockTTL = 5 * time.Minute
	// virtualRefundConfirmTimeout 单轮任务的上下文超时，需给「批量查询 + 并发反查」留足余量。
	virtualRefundConfirmTimeout = 5 * time.Minute
)

// StartVirtualRefundConfirmScheduler 启动虚拟支付退款结果查单兜底任务。
//
// 与发货链路的「推送 + 轮询」双保险同理：退款推送可能丢失、字段版式变化或应答失败重试耗尽，
// 一旦发生订单会永久停留在「6 申请退款中」（用户看不到退款结果、运营无法按状态收口）。
// 本任务对停留超过宽限期的「申请退款中」订单主动反查 query_order：
//   - 微信侧已退款 -> 复用推送同一结算链路置「5 已退款」、回收权益并同步退款流水；
//   - 微信侧仍未退款 -> 保持订单状态不变（避免运营处理中的退款被误判回退），超过阈值输出 Error 告警交人工。
func StartVirtualRefundConfirmScheduler() {
	go func() {
		slog.Info("virtual refund confirm scheduler started")
		for {
			func() {
				defer func() {
					if r := recover(); r != nil {
						slog.Error("virtual refund confirm scheduler panic", "recover", r)
					}
				}()
				runVirtualRefundConfirm()
			}()
			time.Sleep(time.Minute)
		}
	}()
}

// runVirtualRefundConfirm 扫描「申请退款中」的虚拟支付订单并反查微信侧退款结果，单实例通过 Redis 分布式锁防重。
func runVirtualRefundConfirm() {
	// 虚拟支付未开通时直接返回，避免无谓的数据库扫描。
	if !wechat.IsVirtualPayEnabled() {
		return
	}

	ctx, cancel := context.WithTimeout(context.Background(), virtualRefundConfirmTimeout)
	defer cancel()

	ctx, span := global.Tracer.Start(ctx, "scheduler.VirtualRefundConfirm")
	defer span.End()

	lockKey := redismodel.KeyLockVirtualRefundConfirm
	lockVal := genUUID()
	ok, lerr := redisdao.TryLock(ctx, lockKey, lockVal, virtualRefundConfirmLockTTL)
	if lerr != nil {
		slog.ErrorContext(ctx, "virtual refund confirm: acquire lock failed", "error", lerr)
		return
	}
	if !ok {
		slog.DebugContext(ctx, "virtual refund confirm: another instance running, skip")
		return
	}
	defer func() {
		if uerr := redisdao.Unlock(context.Background(), lockKey, lockVal); uerr != nil {
			slog.WarnContext(ctx, "virtual refund confirm: release lock failed", "error", uerr)
		}
	}()

	now := nowUnix()
	orders, err := mysqldao.NewOrderDao().
		OrderListVirtualRefunding(ctx, now-virtualRefundConfirmGraceSeconds, virtualRefundConfirmBatchSize)
	if err != nil {
		slog.ErrorContext(ctx, "virtual refund confirm: list refunding orders failed", "error", err)
		return
	}
	if len(orders) == 0 {
		slog.DebugContext(ctx, "virtual refund confirm: no refunding orders in window")
		return
	}
	if len(orders) >= virtualRefundConfirmBatchSize {
		slog.WarnContext(ctx, "virtual refund confirm backlog detected, candidates reached limit",
			"candidates", len(orders), "limit", virtualRefundConfirmBatchSize)
	}

	s := NewOrderService()
	var (
		mu         sync.Mutex
		wg         sync.WaitGroup
		queried    int
		reconciled int
		stuck      int
	)
	sem := make(chan struct{}, virtualRefundConfirmWorkers)
	for i := range orders {
		order := &orders[i]
		// 频率限制：TTL 内已核对过的订单让出名额；标记不可用时不阻断本轮（退化为重复查询）。
		first, serr := redisdao.VirtualRefundCheckedSetNX(ctx, order.OrderNo, virtualRefundConfirmRecheckTTL)
		if serr != nil {
			slog.WarnContext(ctx, "virtual refund confirm: set recheck mark failed",
				"order_no", order.OrderNo, "error", serr)
		} else if !first {
			continue
		}
		queried++
		wg.Add(1)
		sem <- struct{}{}
		go func(o *mysqlmodel.Order) {
			defer wg.Done()
			defer func() { <-sem }()
			defer func() {
				if r := recover(); r != nil {
					slog.ErrorContext(ctx, "virtual refund confirm worker panic", "order_no", o.OrderNo, "recover", r)
				}
			}()
			done, alerted, qok := s.reconcileVirtualRefund(ctx, o, now)
			if !qok {
				// 查单失败：撤销「已核对」标记，让下一轮立即重试（撤销失败不阻断，退化为 TTL 节奏）。
				if derr := redisdao.VirtualRefundCheckedDel(ctx, o.OrderNo); derr != nil {
					slog.WarnContext(ctx, "virtual refund confirm: clear recheck mark failed",
						"order_no", o.OrderNo, "error", derr)
				}
			}
			if done {
				mu.Lock()
				reconciled++
				mu.Unlock()
			}
			if alerted {
				mu.Lock()
				stuck++
				mu.Unlock()
			}
		}(order)
	}
	wg.Wait()

	if reconciled > 0 || stuck > 0 {
		slog.InfoContext(ctx, "virtual refund confirm finished",
			"scanned", len(orders), "queried", queried, "reconciled", reconciled, "stuck_alerted", stuck)
		return
	}
	slog.DebugContext(ctx, "virtual refund confirm finished without change",
		"scanned", len(orders), "queried", queried)
}

// reconcileVirtualRefund 反查单笔「申请退款中」订单在微信侧的退款结果。
//   - 微信侧已退款：置「已退款」、回收权益并同步退款流水（与推送路径同一结算链路，条件流转天然幂等）；
//   - 微信侧仍未退款：保持订单状态不变，停留超过阈值时输出 Error 告警交人工（不自动回退，避免运营处理中的退款被误判）；
//   - 查询失败/用户信息缺失：仅记日志并返回 queried=false，交由下一轮立即重试。
//
// 返回值：reconciled=已按查单结果订正为已退款；alerted=本次输出了人工介入告警；queried=查单是否成功执行。
func (s *OrderService) reconcileVirtualRefund(ctx context.Context, order *mysqlmodel.Order, now int64) (reconciled bool, alerted bool, queried bool) {
	// query_order 需要 openid，订单表不冗余该字段，按 user_id 取。
	user, err := s.userDao.UserGetByID(ctx, order.UserID)
	if err != nil {
		slog.ErrorContext(ctx, "virtual refund confirm: get user failed",
			"order_no", order.OrderNo, "user_id", order.UserID, "error", err)
		return false, false, false
	}
	if user.WxOpenID == "" {
		slog.WarnContext(ctx, "virtual refund confirm: user openid unavailable",
			"order_no", order.OrderNo, "user_id", order.UserID)
		return false, false, false
	}

	info, qerr := wechat.QueryOrder(ctx, user.WxOpenID, order.OrderNo, "")
	if qerr != nil {
		slog.ErrorContext(ctx, "virtual refund confirm: query order failed",
			"order_no", order.OrderNo, "error", qerr)
		return false, false, false
	}

	if wechat.IsOrderRefundedStatus(info.Order.Status) {
		// 退款金额优先取退款单金额，其次按支付单「实付 - 剩余」推算，最后回退订单实付金额。
		refundFee := info.Order.RefundFee
		if refundFee <= 0 {
			refundFee = info.Order.PaidFee - info.Order.LeftFee
		}
		if refundFee <= 0 {
			refundFee = order.PayAmount
		}
		if serr := s.settleRefundSuccess(ctx, order, refundFee); serr != nil {
			slog.ErrorContext(ctx, "virtual refund confirm: settle refund success failed",
				"order_no", order.OrderNo, "refund_fee", refundFee, "error", serr)
			return false, false, true // 查单成功但结算失败：保持 TTL 节奏重试。
		}
		// 查单分支没有推送报文与微信退款单号，仅同步流水终态（有本地申请流水时）。
		s.markRefundFlowSuccess(ctx, order, "", "")
		slog.InfoContext(ctx, "virtual refund confirm: refund reconciled by query_order",
			"order_no", order.OrderNo, "user_id", order.UserID,
			"wx_status", info.Order.Status, "refund_fee", refundFee)
		return true, false, true
	}

	// 微信侧仍未退款：订单保持「申请退款中」（运营可能正在处理），仅在长期无进展时告警人工介入。
	stuckSeconds := now - order.UpdatedAt
	if stuckSeconds < virtualRefundConfirmStuckSeconds {
		slog.DebugContext(ctx, "virtual refund confirm: refund still pending in wechat side",
			"order_no", order.OrderNo, "wx_status", info.Order.Status, "stuck_seconds", stuckSeconds)
		return false, false, true
	}

	first, serr := redisdao.VirtualRefundStuckAlertSetNX(ctx, order.OrderNo, virtualRefundConfirmStuckAlertTTL)
	if serr != nil {
		slog.WarnContext(ctx, "virtual refund confirm: set stuck alert mark failed",
			"order_no", order.OrderNo, "error", serr)
		first = true // 标记不可用时仍然告警，避免静默。
	}
	if !first {
		return false, false, true
	}
	slog.ErrorContext(ctx, "virtual refund confirm: refund stuck, manual intervention required",
		"order_no", order.OrderNo, "user_id", order.UserID,
		"stuck_seconds", stuckSeconds, "wx_status", info.Order.Status)
	return false, true, true
}