package service

import (
	"errors"
	"strings"
	"time"
	"unicode/utf8"

	"affiliate_dash/internal/model"
	"github.com/google/uuid"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// CancelOrderInput 取消订单的公共输入；开放 API 与商户后台共用同一取消事务。
type CancelOrderInput struct {
	MerchantID  uint
	APIClientID uint
	ActorUserID uint
	OrderNo     string
	Reason      string
	Action      string
}

// CancelOrder 商户开放接口取消订单（审计记录 API 客户端）。
func (s *FulfillmentService) CancelOrder(merchantID, apiClientID uint, orderNo, reason string) (*model.FulfillmentOrder, error) {
	return s.cancelOrder(CancelOrderInput{
		MerchantID:  merchantID,
		APIClientID: apiClientID,
		OrderNo:     orderNo,
		Reason:      reason,
		Action:      "open_order.cancel",
	})
}

// CancelOrderByUser 商户后台取消订单（审计记录操作人）。
func (s *FulfillmentService) CancelOrderByUser(merchantID, actorUserID uint, orderNo, reason string) (*model.FulfillmentOrder, error) {
	return s.cancelOrder(CancelOrderInput{
		MerchantID:  merchantID,
		ActorUserID: actorUserID,
		OrderNo:     orderNo,
		Reason:      reason,
		Action:      "merchant_order.cancel",
	})
}

func (s *FulfillmentService) cancelOrder(in CancelOrderInput) (*model.FulfillmentOrder, error) {
	in.OrderNo = strings.TrimSpace(in.OrderNo)
	in.Reason = strings.TrimSpace(in.Reason)
	if in.MerchantID == 0 || in.OrderNo == "" {
		return nil, errors.New("无效的商户或订单号")
	}
	if utf8.RuneCountInString(in.Reason) > 512 {
		return nil, errors.New("取消原因最长 512 字")
	}
	var out model.FulfillmentOrder
	err := s.db.Transaction(func(tx *gorm.DB) error {
		var order model.FulfillmentOrder
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("merchant_id = ? AND order_no = ?", in.MerchantID, in.OrderNo).
			First(&order).Error; err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return errors.New("订单不存在")
			}
			return err
		}
		if normalizeOrderStatus(&order) == model.OrderStatusCancelled {
			out = order
			return nil
		}
		if err := canCancelOrder(&order); err != nil {
			return err
		}
		// 已提交上游正式订单的失败订单禁止取消：退款后上游仍可能继续发货，造成双重损失。
		// 与发货重试的防重复逻辑（deliverySubmittedUpstream）保持一致。
		if normalizeOrderStatus(&order) == model.OrderStatusShipFailed && deliverySubmittedUpstream(&order) {
			return errors.New("订单已提交上游发货，为避免重复发货无法取消，请先在上游确认订单状态")
		}
		// 先取消上游履约单，避免本地退款后上游仍占库存/资金
		if s.upstreamCancel != nil {
			if err := s.upstreamCancel(&order); err != nil {
				return errors.New("取消上游履约订单失败: " + err.Error())
			}
		}
		now := time.Now()
		updates := map[string]interface{}{"order_status": model.OrderStatusCancelled}
		updates["failure_reason"] = in.Reason
		updates["cancelled_at"] = now
		if err := tx.Model(&order).Updates(updates).Error; err != nil {
			return err
		}
		var wallet model.WalletAccount
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("merchant_id = ?", in.MerchantID).First(&wallet).Error; err != nil {
			return err
		}
		newBalance := wallet.AvailableBalance + order.Amount
		if err := tx.Model(&wallet).Update("available_balance", newBalance).Error; err != nil {
			return err
		}
		idempotencyKey := "cancel:" + order.OrderNo
		if err := tx.Create(&model.WalletLedgerEntry{
			MerchantID:      in.MerchantID,
			WalletAccountID: wallet.ID,
			EntryNo:         "WL" + uuid.NewString(),
			Type:            model.WalletLedgerRefund,
			Amount:          order.Amount,
			BalanceAfter:    newBalance,
			ReferenceType:   "fulfillment_order",
			ReferenceNo:     order.OrderNo,
			IdempotencyKey:  &idempotencyKey,
			Note:            "订单取消退款",
		}).Error; err != nil {
			return err
		}
		var product model.MerchantProduct
		if err := tx.Where("id = ?", order.MerchantProductID).First(&product).Error; err != nil {
			return err
		}
		if product.Stock >= 0 {
			if err := tx.Model(&product).Update("stock", gorm.Expr("stock + ?", order.Quantity)).Error; err != nil {
				return err
			}
		}
		if err := tx.First(&out, order.ID).Error; err != nil {
			return err
		}
		if err := writeAudit(tx, &in.MerchantID, optionalUint(in.ActorUserID), optionalUint(in.APIClientID), in.Action, "fulfillment_order", order.OrderNo, map[string]interface{}{
			"reason": in.Reason,
		}); err != nil {
			return err
		}
		if s.callbacks != nil {
			if err := s.callbacks.Enqueue(tx, in.MerchantID, "order.cancelled", orderCallbackData(&out)); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}
	return &out, nil
}