package services

import (
	"app/commons/core/redisclient"
	"app/commons/model/entity"
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"github.com/shopspring/decimal"
	"gorm.io/gorm"
	"math/big"
	"time"
)

// RedPacketService 红包服务
type RedPacketService struct {
	CommonService
}

// GeneratePacketNo 生成红包编号
func (s *RedPacketService) GeneratePacketNo() string {
	b := make([]byte, 16)
	rand.Read(b)
	return fmt.Sprintf("RP%d%s", time.Now().Unix(), hex.EncodeToString(b)[:16])
}

// CreateRedPacket 创建红包
func (s *RedPacketService) CreateRedPacket(
	userId int64,
	groupId string,
	packetType int,
	totalAmount decimal.Decimal,
	totalCount int,
	symbol string,
	blessingWords string,
) (*entity.TgRedPacket, error) {

	// 参数校验
	if totalAmount.LessThanOrEqual(decimal.Zero) {
		return nil, errors.New("红包金额必须大于0")
	}
	if totalCount <= 0 || totalCount > 100 {
		return nil, errors.New("红包个数必须在1-100之间")
	}
	if packetType != 1 && packetType != 2 {
		return nil, errors.New("红包类型错误")
	}

	// 管理员发红包（userId=0）跳过资产检查和扣款
	isAdmin := userId == 0
	if !isAdmin {
		// 检查用户资产
		userAsset, err := s.GetAssetBySymbol(userId, symbol)
		if err != nil {
			return nil, errors.New("获取资产失败")
		}
		if userAsset.Balance.LessThan(totalAmount) {
			return nil, errors.New("余额不足")
		}
	}

	// 开始事务
	var packet *entity.TgRedPacket
	err := s.DB().Transaction(func(tx *gorm.DB) error {
		// 扣除用户余额（转为冻结），管理员跳过
		if !isAdmin {
			if err := s.ActionAsset(tx, userId, symbol, totalAmount.Neg(), totalAmount); err != nil {
				return fmt.Errorf("扣除余额失败: %w", err)
			}
		}

		// 创建红包记录
		packet = &entity.TgRedPacket{
			PacketNo:      s.GeneratePacketNo(),
			UserId:        userId,
			GroupId:       groupId,
			PacketType:    packetType,
			TotalAmount:   totalAmount,
			TotalCount:    totalCount,
			GrabbedCount:  0,
			GrabbedAmount: decimal.Zero,
			RemainCount:   totalCount,
			RemainAmount:  totalAmount,
			Symbol:        symbol,
			BlessingWords: blessingWords,
			Status:        1, // 进行中
			ExpireAt:      time.Now().Add(24 * time.Hour),
		}

		if err := tx.Create(packet).Error; err != nil {
			return fmt.Errorf("创建红包失败: %w", err)
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	return packet, nil
}

// GrabRedPacket 抢红包
func (s *RedPacketService) GrabRedPacket(
	packetNo string,
	userId int64,
	telegramId int64,
	telegramUsername string,
) (*entity.TgRedPacketRecord, error) {

	// 分布式锁（防止并发抢同一个红包）
	lockKey := fmt.Sprintf("grab_redpacket:%s", packetNo)
	lock, err := redisclient.LockWithTime(lockKey, 5)
	if err != nil {
		return nil, errors.New("系统繁忙，请稍后重试")
	}
	defer redisclient.UnlockSafe(lock)

	// 获取红包信息
	var packet entity.TgRedPacket
	if err := s.DB().Where("packet_no = ?", packetNo).First(&packet).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, errors.New("红包不存在")
		}
		return nil, err
	}

	// 检查红包状态
	if packet.Status != 1 {
		return nil, errors.New("红包已结束")
	}
	if time.Now().After(packet.ExpireAt) {
		return nil, errors.New("红包已过期")
	}
	if packet.RemainCount <= 0 {
		return nil, errors.New("红包已抢完")
	}

	// 检查是否已经抢过（优先用telegramId判断，兼容未绑定平台账号的用户）
	var count int64
	if telegramId > 0 {
		s.DB().Model(&entity.TgRedPacketRecord{}).
			Where("packet_id = ? AND telegram_id = ?", packet.Id, telegramId).
			Count(&count)
	} else {
		s.DB().Model(&entity.TgRedPacketRecord{}).
			Where("packet_id = ? AND user_id = ?", packet.Id, userId).
			Count(&count)
	}
	if count > 0 {
		return nil, errors.New("您已经抢过这个红包了")
	}

	// 开始事务
	var record *entity.TgRedPacketRecord
	err = s.DB().Transaction(func(tx *gorm.DB) error {
		// 计算抢到的金额
		amount := s.CalculateGrabAmount(&packet)

		// 先保存原始值（GORM Updates 会回写到 packet 对象，导致后续判断用到更新后的值）
		origGrabbedCount := packet.GrabbedCount
		origRemainCount := packet.RemainCount

		// 更新红包信息
		updates := map[string]interface{}{
			"grabbed_count":  origGrabbedCount + 1,
			"grabbed_amount": packet.GrabbedAmount.Add(amount),
			"remain_count":   origRemainCount - 1,
			"remain_amount":  packet.RemainAmount.Sub(amount),
		}

		if err := tx.Model(&packet).Updates(updates).Error; err != nil {
			return fmt.Errorf("更新红包失败: %w", err)
		}

		// 创建抢红包记录
		record = &entity.TgRedPacketRecord{
			PacketId:         packet.Id,
			PacketNo:         packet.PacketNo,
			UserId:           userId,
			TelegramId:       telegramId,
			TelegramUsername: telegramUsername,
			Amount:           amount,
			Sequence:         int(origGrabbedCount) + 1,
			GrabbedAt:        time.Now(),
		}

		if err := tx.Create(record).Error; err != nil {
			return fmt.Errorf("创建记录失败: %w", err)
		}

		// 增加用户余额，userId=0 时跳过（Telegram用户未绑定平台账号）
		if userId > 0 {
			// 确保用户有资产记录（不存在则创建）
			var assetCount int64
			tx.Model(&entity.Asset{}).Where("user_id = ? AND symbol = ?", userId, packet.Symbol).Count(&assetCount)
			if assetCount == 0 {
				newAsset := &entity.Asset{
					UserId:  userId,
					Symbol:  packet.Symbol,
					Balance: decimal.Zero,
					Frozen:  decimal.Zero,
				}
				if err := tx.Create(newAsset).Error; err != nil {
					return fmt.Errorf("创建资产记录失败: %w", err)
				}
			}
			if err := s.ActionAsset(tx, userId, packet.Symbol, amount, decimal.Zero); err != nil {
				return fmt.Errorf("增加余额失败: %w", err)
			}
		}

		// 如果抢完了，更新红包状态（使用原始值判断，因为 GORM Updates 已回写 packet）
		if origRemainCount == 1 {
			now := time.Now()
			if err := tx.Model(&packet).Updates(map[string]interface{}{
				"status":       2, // 已抢完
				"completed_at": &now,
			}).Error; err != nil {
				return fmt.Errorf("更新完成状态失败: %w", err)
			}

			// 异步计算手气最佳
			go s.CalculateBestLuck(packet.Id)
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	return record, nil
}

// CalculateGrabAmount 计算抢红包金额
func (s *RedPacketService) CalculateGrabAmount(packet *entity.TgRedPacket) decimal.Decimal {
	// 最后一个红包：剩余所有金额
	if packet.RemainCount == 1 {
		return packet.RemainAmount
	}

	// 普通红包：平均分配
	if packet.PacketType == 1 {
		return packet.RemainAmount.Div(decimal.NewFromInt(int64(packet.RemainCount)))
	}

	// 手气红包：二倍均值算法
	if packet.PacketType == 2 {
		// 平均值
		avg := packet.RemainAmount.Div(decimal.NewFromInt(int64(packet.RemainCount)))
		// 最大值 = 平均值 * 2
		maxAmount := avg.Mul(decimal.NewFromInt(2))

		// 最小值：0.01
		minAmount := decimal.NewFromFloat(0.01)

		// 随机金额：minAmount ~ maxAmount
		randomAmount := s.randomDecimal(minAmount, maxAmount)

		// 确保不超过剩余金额
		if randomAmount.GreaterThan(packet.RemainAmount) {
			return packet.RemainAmount
		}

		return randomAmount
	}

	// 默认平均分配
	return packet.RemainAmount.Div(decimal.NewFromInt(int64(packet.RemainCount)))
}

// randomDecimal 生成随机金额
func (s *RedPacketService) randomDecimal(min, max decimal.Decimal) decimal.Decimal {
	// 计算范围
	diff := max.Sub(min)

	// 生成随机数 0-1
	randomBig, _ := rand.Int(rand.Reader, big.NewInt(10000))
	randomFloat := decimal.NewFromBigInt(randomBig, -4) // 0.0000 - 0.9999

	// 计算随机金额
	amount := min.Add(diff.Mul(randomFloat))

	// 保留2位小数
	return amount.Round(2)
}

// CalculateBestLuck 计算手气最佳
func (s *RedPacketService) CalculateBestLuck(packetId int64) {
	// 查询所有记录
	var records []entity.TgRedPacketRecord
	s.DB().Where("packet_id = ?", packetId).Order("amount DESC").Find(&records)

	if len(records) == 0 {
		return
	}

	// 标记手气最佳（金额最大的）
	bestRecord := records[0]
	s.DB().Model(&entity.TgRedPacketRecord{}).
		Where("id = ?", bestRecord.Id).
		Update("is_best", 1)
}

// GetRedPacketDetail 获取红包详情
func (s *RedPacketService) GetRedPacketDetail(packetNo string) (*entity.TgRedPacket, []entity.TgRedPacketRecord, error) {
	var packet entity.TgRedPacket
	if err := s.DB().Where("packet_no = ?", packetNo).First(&packet).Error; err != nil {
		return nil, nil, err
	}

	var records []entity.TgRedPacketRecord
	s.DB().Where("packet_id = ?", packet.Id).Order("grabbed_at ASC").Find(&records)

	return &packet, records, nil
}

// GetUserRedPacketRecords 获取用户的红包记录
func (s *RedPacketService) GetUserRedPacketRecords(userId int64, page, pageSize int) ([]entity.TgRedPacketRecord, int64, error) {
	var records []entity.TgRedPacketRecord
	var total int64

	db := s.DB().Model(&entity.TgRedPacketRecord{}).Where("user_id = ?", userId)
	db.Count(&total)

	offset := (page - 1) * pageSize
	if err := db.Order("grabbed_at DESC").Offset(offset).Limit(pageSize).Find(&records).Error; err != nil {
		return nil, 0, err
	}

	return records, total, nil
}