basic-banking/src/main/kotlin/ltd/lulz/service/TransactionService.kt

package ltd.lulz.service

import io.github.oshai.kotlinlogging.KotlinLogging
import java.math.BigDecimal
import java.math.BigDecimal.ZERO
import java.util.UUID
import ltd.lulz.exception.InsufficientFundsException
import ltd.lulz.model.AccountEntity
import org.springframework.stereotype.Service
import org.springframework.transaction.annotation.Transactional

private val log = KotlinLogging.logger {}

@Service
class TransactionService(
    private val accountService: AccountService,
) {

    @Transactional
    suspend fun deposit(
        id: UUID,
        amount: BigDecimal,
    ): AccountEntity = accountService.getForUpdateById(id)
        .let {
            log.trace { "Deposited $amount to account ${it.id}" }
            accountService.save(it.copy(amount = it.amount + amount))
        }

    @Transactional
    suspend fun withdrawal(
        account: UUID,
        amount: BigDecimal,
    ): AccountEntity = accountService.getForUpdateById(account)
        .let {
            val entity = it.copy(amount = it.amount - amount)
            if (entity.amount < ZERO) {
                throw InsufficientFundsException()
            }
            log.trace { "withdrawal $amount from account ${it.id}" }
            accountService.save(entity)
        }

    @Transactional
    suspend fun transfer(
        account: UUID,
        receiver: UUID,
        amount: BigDecimal,
    ) {
        withdrawal(account, amount)
        deposit(receiver, amount)
    }
}