interface Transactional {
    fun <T> transaction(action: () -> T): T
}

class TransactionalImpl(private val transactionTemplate: TransactionTemplate): Transactional {
    override fun <T> transaction(action: () -> T): T {
        return transactionTemplate.execute({ action() }) as T
    }
}

@Component
class Api(private val repo: PersonRepository, val transactionTemplate: TransactionTemplate): Transactional by TransactionalImpl(transactionTemplate) {

    @EventListener(ContextRefreshedEvent::class)
    fun expose() {
        get("/") {
            transaction {
                type(contentType = "application/json")

                val p = Person(UUID.randomUUID(), "Nathan", 35)
                repo.save(p)

                repo.findAll().map {
                    PersonDto(it.name, it.tags?.flatMap {
                        it.name?.let { listOf(it) } ?: emptyList()
                    })
                }.toJson()
            }
        }
    }
}