package wallet

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"time"

	"hfb_sys/backend/internal/model"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

type Repository struct {
	db *gorm.DB
}

type Entry struct {
	UserID      uint64
	OrderID     *uint64
	Direction   string
	Amount      float64
	BalanceType string
	BizType     string
	BizNo       string
	Remark      string
}

func NewRepository(db *gorm.DB) *Repository {
	return &Repository{db: db}
}

func (r *Repository) Account(userID uint64) (*AccountDTO, error) {
	var account model.WalletAccount
	err := r.db.Transaction(func(tx *gorm.DB) error {
		if err := ensureAccount(tx, userID); err != nil {
			return err
		}
		return tx.Where("user_id = ?", userID).First(&account).Error
	})
	if err != nil {
		return nil, err
	}
	return toAccountDTO(account), nil
}

func (r *Repository) Ledger(userID uint64) ([]LedgerDTO, error) {
	var rows []model.WalletLedger
	if err := r.db.Where("user_id = ?", userID).Order("id DESC").Limit(100).Find(&rows).Error; err != nil {
		return nil, err
	}
	items := make([]LedgerDTO, 0, len(rows))
	for _, row := range rows {
		items = append(items, toLedgerDTO(row))
	}
	return items, nil
}

func AppendEntries(tx *gorm.DB, entries ...Entry) error {
	for _, entry := range entries {
		if entry.Amount <= 0 {
			continue
		}
		if err := ensureAccount(tx, entry.UserID); err != nil {
			return err
		}
		var account model.WalletAccount
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where("user_id = ?", entry.UserID).First(&account).Error; err != nil {
			return err
		}
		balanceAfter, err := applyEntry(&account, entry)
		if err != nil {
			return err
		}
		if err := tx.Save(&account).Error; err != nil {
			return err
		}
		ledgerNo, err := newLedgerNo()
		if err != nil {
			return err
		}
		ledger := model.WalletLedger{
			LedgerNo:     ledgerNo,
			UserID:       entry.UserID,
			OrderID:      entry.OrderID,
			Direction:    entry.Direction,
			Amount:       entry.Amount,
			BalanceAfter: balanceAfter,
			BalanceType:  entry.BalanceType,
			BizType:      entry.BizType,
			BizNo:        entry.BizNo,
			Remark:       entry.Remark,
		}
		if err := tx.Create(&ledger).Error; err != nil {
			return err
		}
	}
	return nil
}

func ensureAccount(tx *gorm.DB, userID uint64) error {
	account := model.WalletAccount{
		UserID:           userID,
		AvailableBalance: 0,
		FrozenBalance:    0,
		Status:           "active",
	}
	return tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&account).Error
}

func applyEntry(account *model.WalletAccount, entry Entry) (float64, error) {
	switch entry.BalanceType {
	case "available":
		if entry.Direction == "in" {
			account.AvailableBalance += entry.Amount
		} else {
			account.AvailableBalance -= entry.Amount
		}
		return account.AvailableBalance, nil
	case "frozen":
		if entry.Direction == "in" {
			account.FrozenBalance += entry.Amount
		} else {
			account.FrozenBalance -= entry.Amount
		}
		return account.FrozenBalance, nil
	default:
		return 0, fmt.Errorf("unsupported balance type: %s", entry.BalanceType)
	}
}

func toAccountDTO(account model.WalletAccount) *AccountDTO {
	return &AccountDTO{
		UserID:           account.UserID,
		AvailableBalance: account.AvailableBalance,
		FrozenBalance:    account.FrozenBalance,
		Status:           account.Status,
	}
}

func toLedgerDTO(row model.WalletLedger) LedgerDTO {
	return LedgerDTO{
		ID:           row.ID,
		LedgerNo:     row.LedgerNo,
		UserID:       row.UserID,
		OrderID:      row.OrderID,
		Direction:    row.Direction,
		Amount:       row.Amount,
		BalanceAfter: row.BalanceAfter,
		BalanceType:  row.BalanceType,
		BizType:      row.BizType,
		BizNo:        row.BizNo,
		Remark:       row.Remark,
		CreatedAt:    row.CreatedAt,
	}
}

func newLedgerNo() (string, error) {
	buf := make([]byte, 4)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return fmt.Sprintf("WL%d%s", time.Now().UnixNano(), hex.EncodeToString(buf)), nil
}