package paymentsvc

import (
	"context"
	"errors"
	"sync"
)

var ErrPaymentInProgress = errors.New("payment is already in progress")

type Provider interface {
	Sale(ctx context.Context, req SaleRequest) (*Result, error)
}

type Service struct {
	provider Provider

	mu   sync.Mutex
	busy bool
}

func NewService(provider Provider) *Service {
	return &Service{provider: provider}
}

func (s *Service) Sale(ctx context.Context, req SaleRequest) (*Result, error) {
	s.mu.Lock()
	if s.busy {
		s.mu.Unlock()
		return nil, ErrPaymentInProgress
	}
	s.busy = true
	s.mu.Unlock()

	defer func() {
		s.mu.Lock()
		s.busy = false
		s.mu.Unlock()
	}()

	return s.provider.Sale(ctx, req)
}