package refund

import (
	"context"

	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/internal/model/dto"
	"github.com/break/junhong_cmp_fiber/pkg/errors"
)

// refundPackageUsage 是退款展示所需的当前套餐用量。
type refundPackageUsage struct {
	UsedMB  int64
	TotalMB int64
}

// loadRefundPackageUsages 批量解析每个退款申请的「当前退款套餐」用量。
//
// 定位口径与退款套餐失效保持一致，按优先级取唯一一条：
//  1. 退款申请冻结的套餐使用记录（package_usage_id）；
//  2. 该退款关联订单下主套餐使用记录（master_usage_id 为空）；
//  3. 该退款关联订单下任一套餐使用记录。
//
// 同一优先级内按使用记录标识升序取第一条，保证同一退款每次返回相同结果。
// 不按当前生效套餐或当前世代推断，也不跨订单取套餐：换货后权益仍保留原订单关系，
// 按世代推断会指向错误的资产。
//
// 用量的性质是「当前可取得」：不按套餐状态过滤。退款完成后套餐已转已失效，
// 此时仍需展示其用量；若按状态过滤，退款完成后字段会集体归零，与用途矛盾。
//
// 实现固定为两次查询（按标识、按订单），与退款条数无关；解析不到时返回 0 而非报错，
// 使展示增强不阻断列表、详情或导出。
func (s *Service) loadRefundPackageUsages(ctx context.Context, refunds []*model.RefundRequest) (map[uint]refundPackageUsage, error) {
	result := make(map[uint]refundPackageUsage, len(refunds))
	usageIDs := make([]uint, 0, len(refunds))
	orderIDs := make([]uint, 0, len(refunds))
	seenUsage := make(map[uint]struct{}, len(refunds))
	seenOrder := make(map[uint]struct{}, len(refunds))
	for _, refund := range refunds {
		if refund == nil || refund.ID == 0 {
			continue
		}
		result[refund.ID] = refundPackageUsage{}
		if refund.PackageUsageID != nil && *refund.PackageUsageID > 0 {
			if _, exists := seenUsage[*refund.PackageUsageID]; !exists {
				seenUsage[*refund.PackageUsageID] = struct{}{}
				usageIDs = append(usageIDs, *refund.PackageUsageID)
			}
		}
		if refund.OrderID > 0 {
			if _, exists := seenOrder[refund.OrderID]; !exists {
				seenOrder[refund.OrderID] = struct{}{}
				orderIDs = append(orderIDs, refund.OrderID)
			}
		}
	}
	if len(usageIDs) == 0 && len(orderIDs) == 0 {
		return result, nil
	}

	// 第一次查询：按套餐使用记录标识取冻结记录。
	byUsageID := make(map[uint]*model.PackageUsage, len(usageIDs))
	// 第二次查询：按订单取全部候选，再在内存中按优先级择一。
	byOrderID := make(map[uint][]*model.PackageUsage, len(orderIDs))

	if len(usageIDs) > 0 {
		var usages []model.PackageUsage
		if err := s.db.WithContext(ctx).
			Select("id", "order_id", "master_usage_id", "data_usage_mb", "data_limit_mb").
			Where("id IN ?", usageIDs).Find(&usages).Error; err != nil {
			return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询退款套餐使用记录失败")
		}
		for index := range usages {
			byUsageID[usages[index].ID] = &usages[index]
		}
	}
	if len(orderIDs) > 0 {
		var usages []model.PackageUsage
		if err := s.db.WithContext(ctx).
			Select("id", "order_id", "master_usage_id", "data_usage_mb", "data_limit_mb").
			Where("order_id IN ?", orderIDs).
			Order("id ASC").Find(&usages).Error; err != nil {
			return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询退款订单套餐使用记录失败")
		}
		for index := range usages {
			usage := &usages[index]
			byOrderID[usage.OrderID] = append(byOrderID[usage.OrderID], usage)
		}
	}

	for _, refund := range refunds {
		if refund == nil || refund.ID == 0 {
			continue
		}
		usage := resolveRefundPackageUsage(refund, byUsageID, byOrderID)
		if usage == nil {
			continue
		}
		result[refund.ID] = refundPackageUsage{UsedMB: usage.DataUsageMB, TotalMB: usage.DataLimitMB}
	}
	return result, nil
}

// resolveRefundPackageUsage 按优先级为单个退款申请择一当前套餐使用记录。
func resolveRefundPackageUsage(
	refund *model.RefundRequest,
	byUsageID map[uint]*model.PackageUsage,
	byOrderID map[uint][]*model.PackageUsage,
) *model.PackageUsage {
	// 优先级一：冻结的套餐使用记录，且必须属于该退款关联订单（防止跨订单取值）。
	if refund.PackageUsageID != nil && *refund.PackageUsageID > 0 {
		if usage, exists := byUsageID[*refund.PackageUsageID]; exists && usage.OrderID == refund.OrderID {
			return usage
		}
	}
	// 优先级二：订单主套餐；优先级三：订单任一套餐。候选已按标识升序，取首个命中。
	candidates := byOrderID[refund.OrderID]
	if len(candidates) == 0 {
		return nil
	}
	for _, usage := range candidates {
		if usage.MasterUsageID == nil {
			return usage
		}
	}
	return candidates[0]
}

// applyRefundPackageUsage 把解析结果写入响应字段。
func applyRefundPackageUsage(response *dto.RefundResponse, usage refundPackageUsage) {
	if response == nil {
		return
	}
	response.RefundPackageUsedMB = usage.UsedMB
	response.RefundPackageTotalMB = usage.TotalMB
}