package wallet

import (
	"context"
	"crypto/rand"
	"fmt"
	"time"

	"hfb_sys/backend/internal/model"
	"hfb_sys/backend/internal/timeutil"
	"hfb_sys/backend/pkg/money"

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

type Repository struct {
	db *gorm.DB
}

type Entry struct {
	UserID      uint64
	OrderID     *uint64
	Direction   string
	AmountCent  int64
	BalanceType string
	BizType     string
	BizNo       string
	Remark      string
}

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

func (r *Repository) Account(ctx context.Context, userID uint64) (*AccountDTO, error) {
	var account model.WalletAccount
	err := r.db.WithContext(ctx).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(ctx context.Context, userID uint64, page, pageSize int) (*PaginatedResult, error) {
	var total int64
	if err := r.db.WithContext(ctx).Model(&model.WalletLedger{}).Where("user_id = ?", userID).Count(&total).Error; err != nil {
		return nil, err
	}
	offset := (page - 1) * pageSize
	var rows []model.WalletLedger
	if err := r.db.WithContext(ctx).Where("user_id = ?", userID).Order("id DESC").Offset(offset).Limit(pageSize).Find(&rows).Error; err != nil {
		return nil, err
	}
	items := make([]LedgerDTO, 0, len(rows))
	for _, row := range rows {
		items = append(items, toLedgerDTO(row))
	}
	return &PaginatedResult{Items: items, Total: total, Page: page, PageSize: pageSize}, nil
}

// Withdraw 保留仓库能力；当前公开提现入口在 service 层标记为待开发，不会调用到这里。
func (r *Repository) Withdraw(ctx context.Context, userID uint64, amountCent int64) (*AccountDTO, error) {
	if userID == 0 || amountCent <= 0 {
		return nil, ErrInvalidAmount
	}
	err := r.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		return AppendEntries(tx, Entry{
			UserID:      userID,
			Direction:   "out",
			AmountCent:  amountCent,
			BalanceType: "available",
			BizType:     "withdraw_apply",
			BizNo:       fmt.Sprintf("WD%d", time.Now().UnixNano()),
			Remark:      "卖家申请提现",
		})
	})
	if err != nil {
		return nil, err
	}
	return r.Account(ctx, userID)
}

func (r *Repository) AdminLedger(ctx context.Context, query AdminLedgerQuery) (*PaginatedResult, error) {
	db := r.db.WithContext(ctx).Table("wallet_ledger AS wl").
		Select(`wl.id, wl.ledger_no, wl.user_id, COALESCE(u.phone, '') AS user_phone,
			COALESCE(u.nickname, '') AS user_nickname, wl.order_id, COALESCE(ro.order_no, '') AS order_no,
			wl.direction, wl.amount_cent, wl.balance_after_cent, wl.balance_type, wl.biz_type, wl.biz_no,
			wl.remark, wl.created_at`).
		Joins("LEFT JOIN users AS u ON u.id = wl.user_id").
		Joins("LEFT JOIN rental_orders AS ro ON ro.id = wl.order_id")

	countDB := r.db.WithContext(ctx).Model(&model.WalletLedger{})
	if query.UserID > 0 {
		db = db.Where("wl.user_id = ?", query.UserID)
		countDB = countDB.Where("user_id = ?", query.UserID)
	}
	if query.OrderID > 0 {
		db = db.Where("wl.order_id = ?", query.OrderID)
		countDB = countDB.Where("order_id = ?", query.OrderID)
	}
	if query.BizType != "" {
		db = db.Where("wl.biz_type = ?", query.BizType)
		countDB = countDB.Where("biz_type = ?", query.BizType)
	}

	var total int64
	if err := countDB.Count(&total).Error; err != nil {
		return nil, err
	}

	offset := (query.Page - 1) * query.PageSize
	items := make([]AdminLedgerDTO, 0, query.PageSize)
	if err := db.Order("wl.id DESC").Offset(offset).Limit(query.PageSize).Scan(&items).Error; err != nil {
		return nil, err
	}
	return &PaginatedResult{Items: items, Total: total, Page: query.Page, PageSize: query.PageSize}, nil
}

func AppendEntries(tx *gorm.DB, entries ...Entry) error {
	for _, entry := range entries {
		if entry.AmountCent <= 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
		}
		balanceAfterCent, 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,
			AmountCent:       entry.AmountCent,
			BalanceAfterCent: balanceAfterCent,
			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,
		AvailableBalanceCent: 0,
		FrozenBalanceCent:    0,
		Status:               "active",
	}
	return tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&account).Error
}

func applyEntry(account *model.WalletAccount, entry Entry) (int64, error) {
	switch entry.BalanceType {
	case "available":
		if entry.Direction == "in" {
			account.AvailableBalanceCent += entry.AmountCent
		} else {
			if account.AvailableBalanceCent < entry.AmountCent {
				return 0, ErrInsufficientBalance
			}
			account.AvailableBalanceCent -= entry.AmountCent
		}
		return account.AvailableBalanceCent, nil
	case "frozen":
		if entry.Direction == "in" {
			account.FrozenBalanceCent += entry.AmountCent
		} else {
			if account.FrozenBalanceCent < entry.AmountCent {
				return 0, ErrInsufficientBalance
			}
			account.FrozenBalanceCent -= entry.AmountCent
		}
		return account.FrozenBalanceCent, nil
	default:
		return 0, fmt.Errorf("unknown balance type: %s", entry.BalanceType)
	}
}

func roundWalletMoney(yuan float64) float64 {
	return money.Round(yuan)
}

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

func toLedgerDTO(ledger model.WalletLedger) LedgerDTO {
	return LedgerDTO{
		ID:               ledger.ID,
		LedgerNo:         ledger.LedgerNo,
		UserID:           ledger.UserID,
		OrderID:          ledger.OrderID,
		Direction:        ledger.Direction,
		AmountCent:       ledger.AmountCent,
		BalanceAfterCent: ledger.BalanceAfterCent,
		BalanceType:      ledger.BalanceType,
		BizType:          ledger.BizType,
		BizNo:            ledger.BizNo,
		Remark:           ledger.Remark,
		CreatedAt:        ledger.CreatedAt,
	}
}

func newLedgerNo() (string, error) {
	now := timeutil.ShanghaiNow()
	prefix := "WL" + now.Format("20060102150405")
	randomBytes := make([]byte, 4)
	if _, err := rand.Read(randomBytes); err != nil {
		return "", err
	}
	suffix := fmt.Sprintf("%08d", uint32(randomBytes[0])<<24|uint32(randomBytes[1])<<16|uint32(randomBytes[2])<<8|uint32(randomBytes[3]))
	return prefix + suffix[:7], nil
}