package processor

import (
	"context"
	"fmt"
	"strings"
	"time"
	"unicode/utf8"

	"github.com/google/uuid"

	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/entities"
	"apskel-pos-be/internal/models"
	"apskel-pos-be/internal/repository"
)

// walletDescriptionLimit is the size of wallet_transactions.description.
const walletDescriptionLimit = 255

// WalletAdminProcessor serves the dashboard's view of one customer's wallet and the
// manual adjustments an admin makes to it (docs/prd-point-coin.md F7).
type WalletAdminProcessor struct {
	admin  repository.WalletAdminRepository
	query  repository.WalletQueryRepository
	wallet *WalletProcessor
	tx     TxRunner
	now    func() time.Time
}

func NewWalletAdminProcessor(admin repository.WalletAdminRepository, query repository.WalletQueryRepository, wallet *WalletProcessor, tx TxRunner) *WalletAdminProcessor {
	return &WalletAdminProcessor{admin: admin, query: query, wallet: wallet, tx: tx, now: time.Now}
}

// GetCustomerWallet returns the customer's balances, lots and a page of history.
// A customer outside the organization is reported as not found.
func (p *WalletAdminProcessor) GetCustomerWallet(ctx context.Context, organizationID, customerID uuid.UUID, query models.ListCustomerWalletTransactionsQuery) (*models.AdminCustomerWallet, error) {
	filter, page, err := walletTransactionFilter(customerID, query)
	if err != nil {
		return nil, err
	}
	customer, err := p.admin.GetCustomer(ctx, organizationID, customerID)
	if err != nil {
		return nil, err
	}
	now := p.now()

	result := &models.AdminCustomerWallet{
		Customer: models.AdminWalletCustomer{ID: customer.ID, Name: customer.Name, Phone: customer.Phone},
		Lots:     []models.AdminWalletLot{},
	}
	wallet, err := p.admin.GetWallet(ctx, customerID)
	if err != nil {
		return nil, err
	}
	if wallet != nil {
		result.PointBalance = wallet.PointBalance
		result.CoinBalance = wallet.CoinBalance
	}
	spendable, err := p.query.SpendableBalances(ctx, customerID, now)
	if err != nil {
		return nil, err
	}
	result.SpendablePointBalance = spendable[constants.WalletCurrencyPoint]
	result.SpendableCoinBalance = spendable[constants.WalletCurrencyCoin]

	lots, err := p.admin.ListLotsWithBalance(ctx, customerID)
	if err != nil {
		return nil, err
	}
	for _, lot := range lots {
		result.Lots = append(result.Lots, models.AdminWalletLot{
			ID:                  lot.ID,
			Currency:            lot.Currency,
			OriginalAmount:      lot.OriginalAmount,
			RemainingAmount:     lot.RemainingAmount,
			ExpiresAt:           lot.ExpiresAt,
			Expired:             lot.ExpiresAt != nil && !lot.ExpiresAt.After(now),
			SourceTransactionID: lot.SourceTransactionID,
			OriginLotID:         lot.OriginLotID,
			CreatedAt:           lot.CreatedAt,
		})
	}

	rows, total, err := p.query.ListTransactions(ctx, filter)
	if err != nil {
		return nil, err
	}
	transactions, err := p.adminTransactions(ctx, rows)
	if err != nil {
		return nil, err
	}
	result.Transactions = models.PaginatedResponse[models.AdminWalletTransaction]{
		Data: transactions,
		Pagination: models.Pagination{
			Page:       page,
			Limit:      filter.Limit,
			Total:      total,
			TotalPages: int((total + int64(filter.Limit) - 1) / int64(filter.Limit)),
		},
	}
	return result, nil
}

// Adjust adds to or takes from a customer's balance by hand. It is recorded as an
// ADJUSTMENT pointing at the admin, with the reason. Taking more than the customer
// can spend is refused with repository.ErrWalletInsufficientBalance.
func (p *WalletAdminProcessor) Adjust(ctx context.Context, organizationID, adminID, customerID uuid.UUID, in models.WalletAdjustment) (*models.AdminWalletAdjustmentResult, error) {
	reason := strings.TrimSpace(in.Reason)
	if adminID == uuid.Nil {
		return nil, fmt.Errorf("%w: the admin making the adjustment is unknown", ErrWalletInvalidEntry)
	}
	if in.Amount == 0 {
		return nil, fmt.Errorf("%w: amount must not be zero", ErrWalletInvalidEntry)
	}

	entry := WalletEntry{
		CustomerID:    customerID,
		Currency:      in.Currency,
		Type:          constants.WalletTxTypeAdjustment,
		Amount:        abs(in.Amount),
		ReferenceType: constants.WalletRefTypeUser,
		ReferenceID:   adminID,
		CreatedByUser: &adminID,
		Reason:        &reason,
		Description:   truncateRunes("Koreksi oleh admin: "+reason, walletDescriptionLimit),
	}
	if in.IdempotencyKey != "" {
		// Scoped to the customer so a key chosen by the dashboard cannot collide with
		// the keys other flows use.
		entry.IdempotencyKey = fmt.Sprintf("adjust:%s:%s", customerID, in.IdempotencyKey)
	}

	var res *WalletResult
	err := p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		if _, err := p.admin.GetCustomer(ctx, organizationID, customerID); err != nil {
			return err
		}
		var err error
		if in.Amount > 0 {
			// Adjustments never expire until expiry is decided (F12, note N4).
			res, err = p.wallet.Credit(ctx, WalletCreditInput{WalletEntry: entry})
		} else {
			res, err = p.wallet.Debit(ctx, WalletDebitInput{WalletEntry: entry})
		}
		return err
	})
	if err != nil {
		return nil, err
	}

	transactions, err := p.adminTransactions(ctx, []entities.WalletTransaction{*res.Transaction})
	if err != nil {
		return nil, err
	}
	spendable, err := p.query.SpendableBalances(ctx, customerID, p.now())
	if err != nil {
		return nil, err
	}
	return &models.AdminWalletAdjustmentResult{
		Transaction:           transactions[0],
		SpendablePointBalance: spendable[constants.WalletCurrencyPoint],
		SpendableCoinBalance:  spendable[constants.WalletCurrencyCoin],
		Replayed:              res.Replayed,
	}, nil
}

// adminTransactions adds, to what the customer sees, the names behind each row.
func (p *WalletAdminProcessor) adminTransactions(ctx context.Context, rows []entities.WalletTransaction) ([]models.AdminWalletTransaction, error) {
	base, err := buildWalletTransactions(ctx, p.query, rows)
	if err != nil {
		return nil, err
	}

	var customerIDs, userIDs, outletIDs []uuid.UUID
	for _, row := range rows {
		if row.CounterpartyCustomerID != nil {
			customerIDs = append(customerIDs, *row.CounterpartyCustomerID)
		}
		if row.CreatedByUser != nil {
			userIDs = append(userIDs, *row.CreatedByUser)
		}
		if row.OutletID != nil {
			outletIDs = append(outletIDs, *row.OutletID)
		}
	}
	customers, err := p.admin.CustomerNames(ctx, customerIDs)
	if err != nil {
		return nil, err
	}
	users, err := p.admin.UserNames(ctx, userIDs)
	if err != nil {
		return nil, err
	}
	outlets, err := p.admin.OutletNames(ctx, outletIDs)
	if err != nil {
		return nil, err
	}
	named := func(id *uuid.UUID, names map[uuid.UUID]string) *models.AdminWalletNamedRef {
		if id == nil {
			return nil
		}
		return &models.AdminWalletNamedRef{ID: *id, Name: names[*id]}
	}

	out := make([]models.AdminWalletTransaction, 0, len(rows))
	for i, row := range rows {
		out = append(out, models.AdminWalletTransaction{
			CustomerWalletTransaction: base[i],
			Counterparty:              named(row.CounterpartyCustomerID, customers),
			CreatedBy:                 named(row.CreatedByUser, users),
			Outlet:                    named(row.OutletID, outlets),
			Reason:                    row.Reason,
			Metadata:                  row.Metadata,
		})
	}
	return out, nil
}

func truncateRunes(s string, limit int) string {
	if utf8.RuneCountInString(s) <= limit {
		return s
	}
	return string([]rune(s)[:limit])
}