coroutine

src/main/kotlin/ltd/lulz/service/TransactionService.kt

@@ -0,0 +1,52 @@
+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)
+    }
+}