package repository

import (
	"context"
	"fmt"

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

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

// WalletCustomer is the customer a dashboard wallet screen is about.
type WalletCustomer struct {
	ID    uuid.UUID
	Name  string
	Phone *string
}

// WalletAdminRepository serves what the dashboard adds on top of the customer's own
// wallet view (docs/prd-point-coin.md F7): the raw balances, every lot with balance,
// and the real names behind a ledger row. Nothing here changes a balance.
type WalletAdminRepository interface {
	// GetCustomer returns ErrWalletNotFound unless the customer exists and belongs to
	// the organization, so one organization can never read another's customers.
	GetCustomer(ctx context.Context, organizationID, customerID uuid.UUID) (*WalletCustomer, error)
	// GetWallet returns nil, nil for a customer who has never had a wallet.
	GetWallet(ctx context.Context, customerID uuid.UUID) (*entities.CustomerWallet, error)
	// ListLotsWithBalance returns every lot that still holds something, expired or
	// not, in K9 spending order.
	ListLotsWithBalance(ctx context.Context, customerID uuid.UUID) ([]entities.WalletLot, error)
	CustomerNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error)
	UserNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error)
	OutletNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error)
}

type walletAdminRepository struct {
	db *gorm.DB
}

func NewWalletAdminRepository(db *gorm.DB) WalletAdminRepository {
	return &walletAdminRepository{db: db}
}

func (r *walletAdminRepository) GetCustomer(ctx context.Context, organizationID, customerID uuid.UUID) (*WalletCustomer, error) {
	var customers []WalletCustomer
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Table("customers").
		Select("id, name, COALESCE(phone_number, phone) AS phone").
		Where("id = ? AND organization_id = ?", customerID, organizationID).
		Limit(1).
		Scan(&customers).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get customer: %w", err)
	}
	if len(customers) == 0 {
		return nil, ErrWalletNotFound
	}
	return &customers[0], nil
}

func (r *walletAdminRepository) GetWallet(ctx context.Context, customerID uuid.UUID) (*entities.CustomerWallet, error) {
	var wallets []entities.CustomerWallet
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Where("customer_id = ?", customerID).
		Limit(1).
		Find(&wallets).Error
	if err != nil {
		return nil, fmt.Errorf("failed to get customer wallet: %w", err)
	}
	if len(wallets) == 0 {
		return nil, nil
	}
	return &wallets[0], nil
}

func (r *walletAdminRepository) ListLotsWithBalance(ctx context.Context, customerID uuid.UUID) ([]entities.WalletLot, error) {
	var lots []entities.WalletLot
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Where("customer_id = ? AND remaining_amount > 0", customerID).
		Order("currency, 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 *walletAdminRepository) CustomerNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error) {
	return r.names(ctx, "customers", ids)
}

func (r *walletAdminRepository) UserNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error) {
	return r.names(ctx, "users", ids)
}

func (r *walletAdminRepository) OutletNames(ctx context.Context, ids []uuid.UUID) (map[uuid.UUID]string, error) {
	return r.names(ctx, "outlets", ids)
}

// names looks up the name column of a table by id. The table name is never taken
// from user input.
func (r *walletAdminRepository) names(ctx context.Context, table string, ids []uuid.UUID) (map[uuid.UUID]string, error) {
	names := make(map[uuid.UUID]string, len(ids))
	if len(ids) == 0 {
		return names, nil
	}
	var rows []struct {
		ID   string
		Name string
	}
	err := DBFromContext(ctx, r.db).WithContext(ctx).
		Table(table).
		Select("id::text AS id, name").
		Where("id IN ?", ids).
		Scan(&rows).Error
	if err != nil {
		return nil, fmt.Errorf("failed to look up %s names: %w", table, err)
	}
	for _, row := range rows {
		if id, err := uuid.Parse(row.ID); err == nil {
			names[id] = row.Name
		}
	}
	return names, nil
}