package repository

import (
	"context"
	"fmt"
	"time"

	"github.com/google/uuid"
	"gorm.io/gorm"

	"apskel-pos-be/internal/entities"
)

// walletDisplayTimeZone is the zone expiry dates are grouped in for display, the same
// one the database connection uses (config.Database.DSN).
const walletDisplayTimeZone = "Asia/Jakarta"

// WalletTransactionFilter narrows a customer's ledger. Zero values mean no filter.
type WalletTransactionFilter struct {
	CustomerID uuid.UUID
	Currency   string
	Types      []string
	// From is inclusive and To is exclusive.
	From   *time.Time
	To     *time.Time
	Offset int
	Limit  int
}

// WalletExpiringAmount is how much of one currency expires on one day.
type WalletExpiringAmount struct {
	Currency string
	// A calendar date in walletDisplayTimeZone, formatted YYYY-MM-DD.
	Date   string
	Amount int64
}

// WalletQueryRepository serves the read side of the wallet: balances, history and
// upcoming expiry for display. Nothing here changes a balance.
type WalletQueryRepository interface {
	// GetCustomerOrganizationID returns ErrWalletNotFound when the customer does not exist.
	GetCustomerOrganizationID(ctx context.Context, customerID uuid.UUID) (uuid.UUID, error)
	// SpendableBalances sums, per currency, the lots that still have balance and have
	// not expired at asOf. It differs from the wallet balance only for lots that have
	// expired but that the expiry job has not processed yet.
	SpendableBalances(ctx context.Context, customerID uuid.UUID, asOf time.Time) (map[string]int64, error)
	// NearestExpiring returns, per currency, the earliest day after asOf on which some
	// balance expires, and how much expires that day.
	NearestExpiring(ctx context.Context, customerID uuid.UUID, asOf time.Time) ([]WalletExpiringAmount, error)
	// ExpiringByDay returns, per currency and day, everything that expires after asOf,
	// soonest first.
	ExpiringByDay(ctx context.Context, customerID uuid.UUID, asOf time.Time) ([]WalletExpiringAmount, error)
	// ListTransactions returns a page of the ledger, newest first, and the total count.
	ListTransactions(ctx context.Context, filter WalletTransactionFilter) ([]entities.WalletTransaction, int64, error)
	// OrganizationOutstanding sums every wallet balance of an organization.
	OrganizationOutstanding(ctx context.Context, organizationID uuid.UUID) (points, coins int64, err error)
	// ListLotsBySourceTransactions returns the lots created by the given credits.
	ListLotsBySourceTransactions(ctx context.Context, transactionIDs []uuid.UUID) ([]entities.WalletLot, error)
}

type walletQueryRepository struct {
	db *gorm.DB
}

func NewWalletQueryRepository(db *gorm.DB) WalletQueryRepository {
	return &walletQueryRepository{db: db}
}

func (r *walletQueryRepository) GetCustomerOrganizationID(ctx context.Context, customerID uuid.UUID) (uuid.UUID, error) {
	var ids []string
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Table("customers").
		Where("id = ?", customerID).
		Limit(1).
		Pluck("organization_id::text", &ids).Error
	if err != nil {
		return uuid.Nil, fmt.Errorf("failed to get customer organization: %w", err)
	}
	if len(ids) == 0 {
		return uuid.Nil, ErrWalletNotFound
	}
	return uuid.Parse(ids[0])
}

func (r *walletQueryRepository) SpendableBalances(ctx context.Context, customerID uuid.UUID, asOf time.Time) (map[string]int64, error) {
	var rows []struct {
		Currency string
		Amount   int64
	}
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Model(&entities.WalletLot{}).
		Select("currency, SUM(remaining_amount) AS amount").
		Where("customer_id = ? AND remaining_amount > 0", customerID).
		Where("(expires_at IS NULL OR expires_at > ?)", asOf).
		Group("currency").
		Scan(&rows).Error
	if err != nil {
		return nil, fmt.Errorf("failed to sum spendable wallet balance: %w", err)
	}
	balances := make(map[string]int64, len(rows))
	for _, row := range rows {
		balances[row.Currency] = row.Amount
	}
	return balances, nil
}

func (r *walletQueryRepository) NearestExpiring(ctx context.Context, customerID uuid.UUID, asOf time.Time) ([]WalletExpiringAmount, error) {
	var rows []WalletExpiringAmount
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		WITH by_day AS (
			SELECT currency,
				(expires_at AT TIME ZONE ?)::date AS day,
				SUM(remaining_amount) AS amount
			FROM wallet_lots
			WHERE customer_id = ? AND remaining_amount > 0 AND expires_at > ?
			GROUP BY currency, day
		)
		SELECT DISTINCT ON (currency) currency, to_char(day, 'YYYY-MM-DD') AS date, amount
		FROM by_day
		ORDER BY currency, day`, walletDisplayTimeZone, customerID, asOf).
		Scan(&rows).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get nearest expiring wallet balance: %w", err)
	}
	return rows, nil
}

func (r *walletQueryRepository) ListTransactions(ctx context.Context, filter WalletTransactionFilter) ([]entities.WalletTransaction, int64, error) {
	query := DBFromContext(ctx, r.db).WithContext(ctx).
		Model(&entities.WalletTransaction{}).
		Where("customer_id = ?", filter.CustomerID)
	if filter.Currency != "" {
		query = query.Where("currency = ?", filter.Currency)
	}
	if len(filter.Types) > 0 {
		query = query.Where("type IN ?", filter.Types)
	}
	if filter.From != nil {
		query = query.Where("created_at >= ?", *filter.From)
	}
	if filter.To != nil {
		query = query.Where("created_at < ?", *filter.To)
	}

	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, fmt.Errorf("failed to count wallet transactions: %w", err)
	}

	var transactions []entities.WalletTransaction
	err := query.
		Order("created_at DESC, id DESC").
		Offset(filter.Offset).
		Limit(filter.Limit).
		Find(&transactions).Error
	if err != nil {
		return nil, 0, fmt.Errorf("failed to list wallet transactions: %w", err)
	}
	return transactions, total, nil
}

func (r *walletQueryRepository) ListLotsBySourceTransactions(ctx context.Context, transactionIDs []uuid.UUID) ([]entities.WalletLot, error) {
	var lots []entities.WalletLot
	if len(transactionIDs) == 0 {
		return lots, nil
	}
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Where("source_transaction_id IN ?", transactionIDs).
		Order("expires_at NULLS LAST, created_at, id").
		Find(&lots).Error
	if err != nil {
		return nil, fmt.Errorf("failed to list wallet lots: %w", err)
	}
	return lots, nil
}

func (r *walletQueryRepository) OrganizationOutstanding(ctx context.Context, organizationID uuid.UUID) (int64, int64, error) {
	var totals struct{ Points, Coins int64 }
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		SELECT COALESCE(SUM(point_balance), 0) AS points, COALESCE(SUM(coin_balance), 0) AS coins
		FROM customer_wallets WHERE organization_id = ?`, organizationID).Scan(&totals).Error
	if err != nil {
		return 0, 0, fmt.Errorf("failed to sum outstanding balances: %w", err)
	}
	return totals.Points, totals.Coins, nil
}

func (r *walletQueryRepository) ExpiringByDay(ctx context.Context, customerID uuid.UUID, asOf time.Time) ([]WalletExpiringAmount, error) {
	var rows []WalletExpiringAmount
	err := DBFromContext(ctx, r.db).WithContext(ctx).Raw(`
		SELECT currency, to_char((expires_at AT TIME ZONE ?)::date, 'YYYY-MM-DD') AS date,
			SUM(remaining_amount) AS amount
		FROM wallet_lots
		WHERE customer_id = ? AND remaining_amount > 0 AND expires_at > ?
		GROUP BY currency, date
		ORDER BY date, currency`, walletDisplayTimeZone, customerID, asOf).
		Scan(&rows).Error
	if err != nil {
		return nil, fmt.Errorf("failed to list expiring wallet balance: %w", err)
	}
	return rows, nil
}