package net.corda.client.rpc

import net.corda.client.rpc.internal.RPCClient
import net.corda.core.context.Trace
import net.corda.core.crypto.random63BitValue
import net.corda.core.internal.PLATFORM_VERSION
import net.corda.core.internal.concurrent.fork
import net.corda.core.internal.concurrent.transpose
import net.corda.core.messaging.RPCOps
import net.corda.core.serialization.SerializationDefaults
import net.corda.core.serialization.serialize
import net.corda.core.utilities.NetworkHostAndPort
import net.corda.core.utilities.Try
import net.corda.core.utilities.getOrThrow
import net.corda.core.utilities.millis
import net.corda.core.utilities.seconds
import net.corda.node.services.rpc.RPCServerConfiguration
import net.corda.nodeapi.RPCApi
import net.corda.testing.common.internal.eventually
import net.corda.testing.common.internal.succeeds
import net.corda.testing.core.SerializationEnvironmentRule
import net.corda.testing.driver.internal.incrementalPortAllocation
import net.corda.testing.internal.testThreadFactory
import net.corda.testing.node.internal.RPCDriverDSL
import net.corda.testing.node.internal.RpcBrokerHandle
import net.corda.testing.node.internal.RpcServerHandle
import net.corda.testing.node.internal.poll
import net.corda.testing.node.internal.rpcDriver
import net.corda.testing.node.internal.rpcTestUser
import net.corda.testing.node.internal.startRandomRpcClient
import net.corda.testing.node.internal.startRpcClient
import org.apache.activemq.artemis.api.config.ActiveMQDefaultConfiguration
import org.apache.activemq.artemis.api.core.SimpleString
import org.junit.After
import org.junit.Assert.assertEquals
import org.junit.Assert.assertNotNull
import org.junit.Assert.assertTrue
import org.junit.Assert.fail
import org.junit.Ignore
import org.junit.Rule
import org.junit.Test
import rx.Observable
import rx.subjects.PublishSubject
import rx.subjects.UnicastSubject
import java.time.Duration
import java.util.concurrent.ConcurrentLinkedQueue
import java.util.concurrent.Executors
import java.util.concurrent.ScheduledExecutorService
import java.util.concurrent.TimeUnit
import java.util.concurrent.atomic.AtomicInteger
import java.util.concurrent.atomic.AtomicLong

class RPCStabilityTests {
    @Rule
    @JvmField
    val testSerialization = SerializationEnvironmentRule(true)

    private val pool = Executors.newFixedThreadPool(10, testThreadFactory())
    private val portAllocation = incrementalPortAllocation()

    @After
    fun shutdown() {
        pool.shutdown()
    }

    object DummyOps : RPCOps {
        override val protocolVersion = 1000
    }

    private fun waitUntilNumberOfThreadsStable(executorService: ScheduledExecutorService): Map<Thread, List<StackTraceElement>> {
        val values = ConcurrentLinkedQueue<Map<Thread, List<StackTraceElement>>>()
        return poll(executorService, "number of threads to become stable", 250.millis) {
            values.add(Thread.getAllStackTraces().mapValues { it.value.toList() })
            if (values.size > 5) {
                values.poll()
            }
            val first = values.peek()
            if (values.size == 5 && values.all { it.keys.size == first.keys.size }) {
                first
            } else {
                null
            }
        }.get()
    }

    @Test(timeout=300_000)
	fun `client and server dont leak threads`() {
        fun startAndStop() {
            rpcDriver {
                val server = startRpcServer<RPCOps>(ops = DummyOps).get()
                startRpcClient<RPCOps>(server.broker.hostAndPort!!).get()
            }
        }

        runBlockAndCheckThreads(::startAndStop)
    }

    private fun runBlockAndCheckThreads(block: () -> Unit) {
        val executor = Executors.newScheduledThreadPool(1)
        try {
            // Warm-up so that all the thread pools & co. created
            block()

            val threadsBefore = waitUntilNumberOfThreadsStable(executor)
            repeat(5) {
                block()
            }
            val threadsAfter = waitUntilNumberOfThreadsStable(executor)
            val newThreads = threadsAfter.keys.minus(threadsBefore.keys)
            require(newThreads.isEmpty()) {
                "Threads have leaked. New threads created: $newThreads (total before: ${threadsBefore.size}, total after: ${threadsAfter.size})"
            }
        } finally {
            executor.shutdownNow()
        }
    }

    @Test(timeout=300_000)
	fun `client doesnt leak threads when it fails to start`() {
        fun startAndStop() {
            rpcDriver {
                Try.on { startRpcClient<RPCOps>(NetworkHostAndPort("localhost", 9999)).get() }
                val server = startRpcServer<RPCOps>(ops = DummyOps)
                Try.on {
                    startRpcClient<RPCOps>(
                            server.get().broker.hostAndPort!!,
                            configuration = CordaRPCClientConfiguration.DEFAULT.copy(minimumServerProtocolVersion = 1000)
                    ).get()
                }
            }
        }
        runBlockAndCheckThreads(::startAndStop)
    }

    private fun RpcBrokerHandle.getStats(): Map<String, Any> {
        return serverControl.run {
            mapOf(
                    "connections" to listConnectionIDs().toSet(),
                    "sessionCount" to listConnectionIDs().flatMap { listSessions(it).toList() }.size,
                    "consumerCount" to totalConsumerCount
            )
        }
    }

    @Test(timeout=300_000)
	fun `rpc server close doesnt leak broker resources`() {
        rpcDriver {
            fun startAndCloseServer(broker: RpcBrokerHandle) {
                startRpcServerWithBrokerRunning(
                        configuration = RPCServerConfiguration.DEFAULT,
                        ops = DummyOps,
                        brokerHandle = broker
                ).rpcServer.close()
            }

            val broker = startRpcBroker().get()
            startAndCloseServer(broker)
            val initial = broker.getStats()
            repeat(100) {
                startAndCloseServer(broker)
            }
            pollUntilTrue("broker resources to be released") {
                initial == broker.getStats()
            }
        }
    }

    @Test(timeout=300_000)
	fun `rpc client close doesnt leak broker resources`() {
        rpcDriver {
            val server = startRpcServer(configuration = RPCServerConfiguration.DEFAULT, ops = DummyOps).get()
            RPCClient<RPCOps>(server.broker.hostAndPort!!).start(RPCOps::class.java, rpcTestUser.username, rpcTestUser.password).close()
            val initial = server.broker.getStats()
            repeat(100) {
                val connection = RPCClient<RPCOps>(server.broker.hostAndPort!!).start(RPCOps::class.java, rpcTestUser.username, rpcTestUser.password)
                connection.close()
            }
            pollUntilTrue("broker resources to be released") {
                initial == server.broker.getStats()
            }
        }
    }

    @Test(timeout=300_000)
	fun `rpc server close is idempotent`() {
        rpcDriver {
            val server = startRpcServer(ops = DummyOps).get()
            repeat(10) {
                server.rpcServer.close()
            }
        }
    }

    @Test(timeout=300_000)
	fun `rpc client close is idempotent`() {
        rpcDriver {
            val serverShutdown = shutdownManager.follower()
            val server = startRpcServer(ops = DummyOps).get()
            serverShutdown.unfollow()
            // With the server up
            val connection1 = RPCClient<RPCOps>(server.broker.hostAndPort!!).start(RPCOps::class.java, rpcTestUser.username, rpcTestUser.password)
            repeat(10) {
                connection1.close()
            }
            val connection2 = RPCClient<RPCOps>(server.broker.hostAndPort!!).start(RPCOps::class.java, rpcTestUser.username, rpcTestUser.password)
            serverShutdown.shutdown()
            // With the server down
            repeat(10) {
                connection2.close()
            }
        }
    }

    interface LeakObservableOps : RPCOps {
        fun leakObservable(): Observable<Nothing>
    }

    @Test(timeout=300_000)
	fun `client cleans up leaked observables`() {
        rpcDriver {
            val leakObservableOpsImpl = object : LeakObservableOps {
                val leakedUnsubscribedCount = AtomicInteger(0)
                override val protocolVersion = 1000
                override fun leakObservable(): Observable<Nothing> {
                    return PublishSubject.create<Nothing>().doOnUnsubscribe {
                        leakedUnsubscribedCount.incrementAndGet()
                    }
                }
            }
            val server = startRpcServer<LeakObservableOps>(ops = leakObservableOpsImpl)
            val proxy = startRpcClient<LeakObservableOps>(server.get().broker.hostAndPort!!).get()
            // Leak many observables
            val count = 200
            (1..count).map {
                pool.fork { proxy.leakObservable(); Unit }
            }.transpose().getOrThrow()
            // In a loop force GC and check whether the server is notified
            while (true) {
                System.gc()
                if (leakObservableOpsImpl.leakedUnsubscribedCount.get() == count) break
                Thread.sleep(100)
            }
        }
    }

    interface ReconnectOps : RPCOps {
        fun ping(): String
    }

    @Test(timeout=300_000)
	fun `client reconnects to rebooted server`() {
        rpcDriver {
            val ops = object : ReconnectOps {
                override val protocolVersion = 1000
                override fun ping() = "pong"
            }

            val serverFollower = shutdownManager.follower()
            val serverPort = startRpcServer<ReconnectOps>(ops = ops).getOrThrow().broker.hostAndPort!!
            serverFollower.unfollow()
            // Set retry interval to 1s to reduce test duration
            val clientConfiguration = CordaRPCClientConfiguration.DEFAULT.copy(connectionRetryInterval = 1.seconds)
            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<ReconnectOps>(serverPort, configuration = clientConfiguration).getOrThrow()
            clientFollower.unfollow()
            assertEquals("pong", client.ping())
            serverFollower.shutdown()
            startRpcServer<ReconnectOps>(ops = ops, customPort = serverPort).getOrThrow()
            val response = eventually {
                succeeds { client.ping() }
            }
            assertEquals("pong", response)
            clientFollower.shutdown() // Driver would do this after the new server, causing hang.
        }
    }

    @Test(timeout=300_000)
	fun `connection failover fails, rpc calls throw`() {
        rpcDriver {
            val ops = object : ReconnectOps {
                override val protocolVersion = 1000
                override fun ping() = "pong"
            }

            val serverFollower = shutdownManager.follower()
            val serverPort = startRpcServer<ReconnectOps>(ops = ops).getOrThrow().broker.hostAndPort!!
            serverFollower.unfollow()
            // Set retry interval to 1s to reduce test duration
            val clientConfiguration = CordaRPCClientConfiguration.DEFAULT.copy(connectionRetryInterval = 1.seconds, maxReconnectAttempts = 5)
            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<ReconnectOps>(serverPort, configuration = clientConfiguration).getOrThrow()
            clientFollower.unfollow()
            assertEquals("pong", client.ping())
            serverFollower.shutdown()
            try {
                client.ping()
            } catch (e: Exception) {
                assertTrue(e is RPCException)
            }
            clientFollower.shutdown() // Driver would do this after the new server, causing hang.
        }
    }

    @Test(timeout=300_000)
	fun `connection exits when bad config means the exception is unrecoverable`() {
        rpcDriver {
            val ops = object : ReconnectOps {
                override val protocolVersion = 1000
                override fun ping() = "pong"
            }

            val serverPort = startRpcServer<ReconnectOps>(ops = ops).getOrThrow().broker.hostAndPort!!
            val clientConfiguration = CordaRPCClientConfiguration.DEFAULT.copy(minimumServerProtocolVersion = PLATFORM_VERSION + 1)
            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<ReconnectOps>(serverPort, configuration = clientConfiguration).getOrThrow()
            try {
                client.ping()
            } catch (e: Exception) {
                assertTrue(e is RPCException)
                assertTrue(e.cause is UnrecoverableRPCException)
                assertEquals(e.message, "Requested minimum protocol version " +
                        "(${PLATFORM_VERSION}) is higher than the server's supported protocol version (${PLATFORM_VERSION +1})")
            }
            clientFollower.unfollow()
            clientFollower.shutdown() // Driver would do this after the new server, causing hang.
        }
    }

    interface NoOps : RPCOps {
        fun subscribe(): Observable<Nothing>
    }

    @Test(timeout=300_000)
	fun `observables error when connection breaks`() {
        rpcDriver {
            val ops = object : NoOps {
                override val protocolVersion = 1000
                override fun subscribe(): Observable<Nothing> {
                    return PublishSubject.create<Nothing>()
                }
            }
            val serverFollower = shutdownManager.follower()
            val serverPort = startRpcServer<NoOps>(ops = ops).getOrThrow().broker.hostAndPort!!
            serverFollower.unfollow()

            val clientConfiguration = CordaRPCClientConfiguration.DEFAULT.copy(connectionRetryInterval = 500.millis, maxReconnectAttempts = 1)
            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<NoOps>(serverPort, configuration = clientConfiguration).getOrThrow()
            clientFollower.unfollow()

            var terminateHandlerCalled = false
            var errorHandlerCalled = false
            var exceptionMessage: String? = null
            val subscription = client.subscribe()
                     .doOnTerminate{ terminateHandlerCalled = true }
                     .subscribe({}, {
                         errorHandlerCalled = true
                         //log exception
                         exceptionMessage = it.message
                     })

            serverFollower.shutdown()

            eventually {
                assertTrue(terminateHandlerCalled)
                assertTrue(errorHandlerCalled)
                assertEquals("Connection failure detected.", exceptionMessage)
                assertTrue(subscription.isUnsubscribed)
            }
            clientFollower.shutdown() // Driver would do this after the new server, causing hang.
        }
    }

    @Test(timeout=300_000)
	fun `client throws RPCException after initial connection attempt fails`() {
        val client = CordaRPCClient(portAllocation.nextHostAndPort())
        var exceptionMessage: String? = null
        try {
           client.start("user", "pass").proxy
        } catch (e1: RPCException) {
            exceptionMessage = e1.message
        } catch (e2: Exception) {
            fail("Expected RPCException to be thrown. Received ${e2.javaClass.simpleName} instead.")
        }
        assertNotNull(exceptionMessage)
        assertEquals("Cannot connect to server(s). Tried with all available servers.", exceptionMessage)
    }

    interface ServerOps : RPCOps {
        fun serverId(): String
    }

    @Test(timeout=300_000)
	fun `client connects to first available server`() {
        rpcDriver {
            val ops = object : ServerOps {
                override val protocolVersion = 1000
                override fun serverId() = "server"
            }
            val serverFollower = shutdownManager.follower()
            val serverAddress = startRpcServer<RPCOps>(ops = ops).getOrThrow().broker.hostAndPort!!
            serverFollower.unfollow()

            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<ServerOps>(listOf(NetworkHostAndPort("localhost", 12345), serverAddress, NetworkHostAndPort("localhost", 54321))).getOrThrow()
            clientFollower.unfollow()

            assertEquals("server", client.serverId())

            clientFollower.shutdown() // Driver would do this after the new server, causing hang.
        }
    }

    @Test(timeout=300_000)
	fun `3 server failover`() {
        rpcDriver {
            val ops1 = object : ServerOps {
                override val protocolVersion = 1000
                override fun serverId() = "server1"
            }
            val ops2 = object : ServerOps {
                override val protocolVersion = 1000
                override fun serverId() = "server2"
            }
            val ops3 = object : ServerOps {
                override val protocolVersion = 1000
                override fun serverId() = "server3"
            }
            val serverFollower1 = shutdownManager.follower()
            val server1 = startRpcServer<RPCOps>(ops = ops1).getOrThrow()
            serverFollower1.unfollow()

            val serverFollower2 = shutdownManager.follower()
            val server2 = startRpcServer<RPCOps>(ops = ops2).getOrThrow()
            serverFollower2.unfollow()

            val serverFollower3 = shutdownManager.follower()
            val server3 = startRpcServer<RPCOps>(ops = ops3).getOrThrow()
            serverFollower3.unfollow()
            val servers = mutableMapOf("server1" to serverFollower1, "server2" to serverFollower2, "server3" to serverFollower3)

            val clientFollower = shutdownManager.follower()
            val client = startRpcClient<ServerOps>(listOf(server1.broker.hostAndPort!!, server2.broker.hostAndPort!!, server3.broker.hostAndPort!!)).getOrThrow()
            clientFollower.unfollow()

            var response = client.serverId()
            assertTrue(servers.containsKey(response))
            servers[response]!!.shutdown()
            servers.remove(response)

            // Failover will take some time.
            while (true) {
                try {
                    response = client.serverId()
                    break
                } catch (e: RPCException) {}
            }
            assertTrue(servers.containsKey(response))
            servers[response]!!.shutdown()
            servers.remove(response)

            while (true) {
                try {
                    response = client.serverId()
                    break
                } catch (e: RPCException) {}
            }
            assertTrue(servers.containsKey(response))
            servers[response]!!.shutdown()
            servers.remove(response)

            assertTrue(servers.isEmpty())

            clientFollower.shutdown() // Driver would do this after the new server, causing hang.

        }
    }

    interface TrackSubscriberOps : RPCOps {
        fun subscribe(): Observable<Unit>
    }

    /**
     * In this test we create a number of out of process RPC clients that call [TrackSubscriberOps.subscribe] in a loop.
     */
    @Test(timeout=300_000)
	fun `server cleans up queues after disconnected clients`() {
        rpcDriver {
            val trackSubscriberOpsImpl = object : TrackSubscriberOps {
                override val protocolVersion = 1000
                val subscriberCount = AtomicInteger(0)
                val trackSubscriberCountObservable = UnicastSubject.create<Unit>().share().
                        doOnSubscribe { subscriberCount.incrementAndGet() }.
                        doOnUnsubscribe { subscriberCount.decrementAndGet() }

                override fun subscribe(): Observable<Unit> {
                    return trackSubscriberCountObservable
                }
            }
            val server = startRpcServer<TrackSubscriberOps>(
                    configuration = RPCServerConfiguration.DEFAULT.copy(
                            reapInterval = 100.millis
                    ),
                    ops = trackSubscriberOpsImpl
            ).get()

            val numberOfClients = 4
            val clients = (1..numberOfClients).map {
                startRandomRpcClient<TrackSubscriberOps>(server.broker.hostAndPort!!)
            }.transpose().get()

            // Poll until all clients connect
            pollUntilClientNumber(server, numberOfClients)
            pollUntilTrue("number of times subscribe() has been called") { trackSubscriberOpsImpl.subscriberCount.get() >= 100 }.get()
            // Kill one client
            clients[0].destroyForcibly()
            pollUntilClientNumber(server, numberOfClients - 1)
            // Kill the rest
            (1 until numberOfClients).forEach {
                clients[it].destroyForcibly()
            }
            pollUntilClientNumber(server, 0)
            // Now poll until the server detects the disconnects and un-subscribes from all observables.
            pollUntilTrue("number of times subscribe() has been called") { trackSubscriberOpsImpl.subscriberCount.get() == 0 }.get()
        }
    }

    interface SlowConsumerRPCOps : RPCOps {
        fun streamAtInterval(interval: Duration, size: Int): Observable<ByteArray>
    }

    class SlowConsumerRPCOpsImpl : SlowConsumerRPCOps {
        override val protocolVersion = 1000

        override fun streamAtInterval(interval: Duration, size: Int): Observable<ByteArray> {
            val chunk = ByteArray(size)
            return Observable.interval(interval.toMillis(), TimeUnit.MILLISECONDS).map { chunk }
        }
    }

    @Test(timeout=300_000)
@Ignore // TODO: This is ignored because Artemis slow consumers are broken.  I'm not deleting it in case we can get the feature fixed.
    fun `slow consumers are kicked`() {
        rpcDriver {
            val server = startRpcServer(maxBufferedBytesPerClient = 10 * 1024 * 1024, ops = SlowConsumerRPCOpsImpl()).get()

            // Construct an RPC session manually so that we can hang in the message handler
            val myQueue = "${RPCApi.RPC_CLIENT_QUEUE_NAME_PREFIX}.test.${random63BitValue()}"
            val session = startArtemisSession(server.broker.hostAndPort!!)
            session.createTemporaryQueue(myQueue, ActiveMQDefaultConfiguration.getDefaultRoutingType(), myQueue)
            val consumer = session.createConsumer(myQueue, null, -1, -1, false)
            consumer.setMessageHandler {
                Thread.sleep(5000) // Needs to be slower than one per second to get kicked.
                it.acknowledge()
            }
            val producer = session.createProducer(RPCApi.RPC_SERVER_QUEUE_NAME)
            session.start()

            pollUntilClientNumber(server, 1)

            val message = session.createMessage(false)
            val request = RPCApi.ClientToServer.RpcRequest(
                    clientAddress = SimpleString(myQueue),
                    methodName = SlowConsumerRPCOps::streamAtInterval.name,
                    serialisedArguments = listOf(100.millis, 1234).serialize(context = SerializationDefaults.RPC_SERVER_CONTEXT),
                    replyId = Trace.InvocationId.newInstance(),
                    sessionId = Trace.SessionId.newInstance()
            )
            request.writeToClientMessage(message)
            message.putLongProperty(RPCApi.DEDUPLICATION_SEQUENCE_NUMBER_FIELD_NAME, 0)
            producer.send(message)
            session.commit()

            // We are consuming slower than the server is producing, so we should be kicked after a while if slow consumers are enabled.
            pollUntilClientNumber(server, 0)
        }
    }

    @Test(timeout=300_000)
	fun `deduplication in the server`() {
        rpcDriver {
            val server = startRpcServer(ops = SlowConsumerRPCOpsImpl()).getOrThrow()

            // Construct an RPC client session manually
            val myQueue = "${RPCApi.RPC_CLIENT_QUEUE_NAME_PREFIX}.test.${random63BitValue()}"
            val session = startArtemisSession(server.broker.hostAndPort!!)
            session.createTemporaryQueue(myQueue, ActiveMQDefaultConfiguration.getDefaultRoutingType(), myQueue)
            val consumer = session.createConsumer(myQueue, null, -1, -1, false)
            val replies = ArrayList<Any>()
            consumer.setMessageHandler {
                replies.add(it)
                it.acknowledge()
            }

            val producer = session.createProducer(RPCApi.RPC_SERVER_QUEUE_NAME)
            session.start()

            pollUntilClientNumber(server, 1)

            val message = session.createMessage(false)
            val request = RPCApi.ClientToServer.RpcRequest(
                    clientAddress = SimpleString(myQueue),
                    methodName = DummyOps::protocolVersion.name,
                    serialisedArguments = emptyList<Any>().serialize(context = SerializationDefaults.RPC_SERVER_CONTEXT),
                    replyId = Trace.InvocationId.newInstance(),
                    sessionId = Trace.SessionId.newInstance()
            )
            request.writeToClientMessage(message)
            message.putLongProperty(RPCApi.DEDUPLICATION_SEQUENCE_NUMBER_FIELD_NAME, 0)
            producer.send(message)
            // duplicate the message
            producer.send(message)

            pollUntilTrue("Number of replies is 1") {
                replies.size == 1
            }.getOrThrow()
        }
    }

    @Test(timeout=300_000)
	fun `deduplication in the client`() {
        rpcDriver {
            val broker = startRpcBroker().getOrThrow()

            // Construct an RPC server session manually
            val session = startArtemisSession(broker.hostAndPort!!)
            val consumer = session.createConsumer(RPCApi.RPC_SERVER_QUEUE_NAME)
            val producer = session.createProducer()
            val dedupeId = AtomicLong(0)
            consumer.setMessageHandler {
                it.acknowledge()
                val request = RPCApi.ClientToServer.fromClientMessage(it)
                when (request) {
                    is RPCApi.ClientToServer.RpcRequest -> {
                        val reply = RPCApi.ServerToClient.RpcReply(request.replyId, Try.Success(1000), "server")
                        val message = session.createMessage(false)
                        reply.writeToClientMessage(SerializationDefaults.RPC_SERVER_CONTEXT, message)
                        message.putLongProperty(RPCApi.DEDUPLICATION_SEQUENCE_NUMBER_FIELD_NAME, dedupeId.getAndIncrement())
                        producer.send(request.clientAddress, message)
                        // duplicate the reply
                        producer.send(request.clientAddress, message)
                    }
                    is RPCApi.ClientToServer.ObservablesClosed -> {
                    }
                }
            }
            session.start()

            startRpcClient<RPCOps>(broker.hostAndPort!!).getOrThrow()
        }
    }
}

fun RPCDriverDSL.pollUntilClientNumber(server: RpcServerHandle, expected: Int) {
    pollUntilTrue("number of RPC clients to become $expected") {
        val clientAddresses = server.broker.serverControl.addressNames.filter { it.startsWith(RPCApi.RPC_CLIENT_QUEUE_NAME_PREFIX) }
        clientAddresses.size == expected
    }.get()
}