/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2012, Red Hat, Inc., and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.jboss.as.host.controller.mgmt;

import static org.jboss.as.controller.descriptions.ModelDescriptionConstants.EXTENSION;
import static org.jboss.as.controller.descriptions.ModelDescriptionConstants.FAILED;
import static org.jboss.as.controller.descriptions.ModelDescriptionConstants.FAILURE_DESCRIPTION;
import static org.jboss.as.controller.descriptions.ModelDescriptionConstants.OUTCOME;
import static org.jboss.as.host.controller.HostControllerLogger.DOMAIN_LOGGER;
import static org.jboss.as.process.protocol.ProtocolUtils.expectHeader;

import java.io.DataInput;
import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicBoolean;

import org.jboss.as.controller.ModelController;
import org.jboss.as.controller.ModelVersion;
import org.jboss.as.controller.OperationContext;
import org.jboss.as.controller.OperationFailedException;
import org.jboss.as.controller.OperationStepHandler;
import org.jboss.as.controller.PathAddress;
import org.jboss.as.controller.PathElement;
import org.jboss.as.controller.RunningMode;
import org.jboss.as.controller.client.OperationAttachments;
import org.jboss.as.controller.client.OperationMessageHandler;
import org.jboss.as.controller.descriptions.ModelDescriptionConstants;
import org.jboss.as.controller.registry.Resource;
import org.jboss.as.controller.remote.TransactionalProtocolClient;
import org.jboss.as.controller.transform.TransformationTarget;
import org.jboss.as.controller.transform.TransformationTargetImpl;
import org.jboss.as.controller.transform.TransformerRegistry;
import org.jboss.as.controller.transform.Transformers;
import org.jboss.as.domain.controller.DomainController;
import org.jboss.as.domain.controller.DomainControllerMessages;
import org.jboss.as.domain.controller.SlaveRegistrationException;
import org.jboss.as.domain.controller.operations.ReadMasterDomainModelHandler;
import org.jboss.as.host.controller.HostControllerMessages;
import org.jboss.as.protocol.ProtocolLogger;
import org.jboss.as.protocol.StreamUtils;
import org.jboss.as.protocol.mgmt.ActiveOperation;
import org.jboss.as.protocol.mgmt.FlushableDataOutput;
import org.jboss.as.protocol.mgmt.ManagementChannelHandler;
import org.jboss.as.protocol.mgmt.ManagementProtocol;
import org.jboss.as.protocol.mgmt.ManagementRequestContext;
import org.jboss.as.protocol.mgmt.ManagementRequestHandler;
import org.jboss.as.protocol.mgmt.ManagementRequestHandlerFactory;
import org.jboss.as.protocol.mgmt.ManagementRequestHeader;
import org.jboss.as.protocol.mgmt.ManagementResponseHeader;
import org.jboss.dmr.ModelNode;
import org.jboss.dmr.Property;
import org.jboss.remoting3.Channel;
import org.jboss.remoting3.CloseHandler;
import org.jboss.threads.AsyncFutureTask;

/**
 * Handler responsible for the host-controller registration process. This may involve assembling the correct
 * {@code ManagementRequestHandlerFactory} based on the version of the host-controller registering.
 *
 * @author Emanuel Muckenhuber
 */
public class HostControllerRegistrationHandler implements ManagementRequestHandlerFactory {

    private static final ModelNode READ_DOMAIN_MODEL = new ModelNode();
    static {
        READ_DOMAIN_MODEL.get(ModelDescriptionConstants.OP).set(ReadMasterDomainModelHandler.OPERATION_NAME);
        READ_DOMAIN_MODEL.get(ModelDescriptionConstants.OP_ADDR).setEmptyList();
        READ_DOMAIN_MODEL.protect();
    }

    private final ManagementChannelHandler handler;
    private final OperationExecutor operationExecutor;
    private final DomainController domainController;
    private final Executor registrations;
    private final DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry;

    public HostControllerRegistrationHandler(ManagementChannelHandler handler, DomainController domainController, OperationExecutor operationExecutor, Executor registrations, DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry) {
        this.handler = handler;
        this.operationExecutor = operationExecutor;
        this.domainController = domainController;
        this.registrations = registrations;
        this.runtimeIgnoreTransformationRegistry = runtimeIgnoreTransformationRegistry;
    }

    @Override
    public ManagementRequestHandler<?, ?> resolveHandler(final RequestHandlerChain handlers, final ManagementRequestHeader header) {
        if (header.getVersion() != 1) {
            // Send subject
            handler.getAttachments().attach(TransactionalProtocolClient.SEND_SUBJECT, Boolean.TRUE);
        }
        final byte operationId = header.getOperationId();
        switch (operationId) {
            case DomainControllerProtocol.REGISTER_HOST_CONTROLLER_REQUEST: {
                // Start the registration process
                final RegistrationContext context = new RegistrationContext(domainController.getExtensionRegistry().getTransformerRegistry(), runtimeIgnoreTransformationRegistry);
                context.activeOperation = handlers.registerActiveOperation(header.getBatchId(), context, context);
                return new InitiateRegistrationHandler();
            }
            case DomainControllerProtocol.FETCH_DOMAIN_CONFIGURATION_REQUEST: {
                // Start the fetch the domain model process
                final RegistrationContext context = new RegistrationContext(domainController.getExtensionRegistry().getTransformerRegistry());
                context.activeOperation = handlers.registerActiveOperation(header.getBatchId(), context, context);
                return new InitiateRegistrationHandler();
            }
            case DomainControllerProtocol.REQUEST_SUBSYSTEM_VERSIONS:
                // register the subsystem versions
                return new RegisterSubsystemVersionsHandler();
            case DomainControllerProtocol.COMPLETE_HOST_CONTROLLER_REGISTRATION:
                // Complete the registration process
                return new CompleteRegistrationHandler();
        }
        return handlers.resolveNext();
    }

    /**
     * wrapper to the DomainController and the underlying {@code ModelController} to execute
     * a {@code OperationStepHandler} implementation directly, bypassing normal domain coordination layer.
     */
    public interface OperationExecutor {

        /**
         * Execute the operation.
         *
         * @param operation operation
         * @param handler the message handler
         * @param control the transaction control
         * @param attachments the operation attachments
         * @param step the step to be executed
         * @return the result
         */
        ModelNode execute(ModelNode operation, OperationMessageHandler handler, ModelController.OperationTransactionControl control, OperationAttachments attachments, OperationStepHandler step);

        /**
         * Join an existing operation, which is currently being executed.
         *
         * @param operation the operation
         * @param handler the message handler
         * @param control the transaction control
         * @param attachments the operation attachments
         * @param step the step to be executed
         * @param permit the operation permit to join
         * @return the result
         */
        ModelNode joinActiveOperation(ModelNode operation, OperationMessageHandler handler, ModelController.OperationTransactionControl control, OperationAttachments attachments, OperationStepHandler step, int permit);

    }

    class InitiateRegistrationHandler implements ManagementRequestHandler<Void, RegistrationContext> {

        @Override
        public void handleRequest(final DataInput input, final ActiveOperation.ResultHandler<Void> resultHandler, final ManagementRequestContext<RegistrationContext> context) throws IOException {
            expectHeader(input, DomainControllerProtocol.PARAM_HOST_ID);
            final String hostName = input.readUTF();
            final ModelNode hostInfo = new ModelNode();
            hostInfo.readExternal(input);

            final RegistrationContext registration = context.getAttachment();
            registration.initialize(hostName, hostInfo, context);

            if (domainController.getCurrentRunningMode() == RunningMode.ADMIN_ONLY) {
                registration.failed(SlaveRegistrationException.ErrorCode.MASTER_IS_ADMIN_ONLY, DomainControllerMessages.MESSAGES.adminOnlyModeCannotAcceptSlaves(RunningMode.ADMIN_ONLY));
                return;
            }
            if (!domainController.getLocalHostInfo().isMasterDomainController()) {
                registration.failed(SlaveRegistrationException.ErrorCode.HOST_IS_NOT_MASTER, DomainControllerMessages.MESSAGES.slaveControllerCannotAcceptOtherSlaves());
                return;
            }

            // Read the domain model async, this will block until the registration process is complete
            context.executeAsync(new ManagementRequestContext.AsyncTask<RegistrationContext>() {
                @Override
                public void execute(ManagementRequestContext<RegistrationContext> context) throws Exception {
                    registration.processRegistration();
                }
            }, registrations);

        }

    }

    class RegisterSubsystemVersionsHandler implements ManagementRequestHandler<Void, RegistrationContext> {

        @Override
        public void handleRequest(DataInput input, ActiveOperation.ResultHandler<Void> resultHandler, ManagementRequestContext<RegistrationContext> context) throws IOException {
            final byte status = input.readByte();
            final ModelNode subsystems = new ModelNode();
            subsystems.readExternal(input);

            final RegistrationContext registration = context.getAttachment();
            if(status == DomainControllerProtocol.PARAM_OK) {
                registration.setSubsystems(subsystems, context);
            } else {
                registration.setSubsystems(null, context);
            }
        }

    }

    /**
     * Handler responsible for completing the registration request.
     */
    static class CompleteRegistrationHandler implements ManagementRequestHandler<Void, RegistrationContext> {

        @Override
        public void handleRequest(final DataInput input, final ActiveOperation.ResultHandler<Void> resultHandler, final ManagementRequestContext<RegistrationContext> context) throws IOException {
            final byte status = input.readByte();
            final String message = input.readUTF(); // Perhaps use message when the host failed
            final RegistrationContext registration = context.getAttachment();
            // Complete the registration
            registration.completeRegistration(context, status == DomainControllerProtocol.PARAM_OK);
        }

    }

    class HostRegistrationStepHandler implements OperationStepHandler {
        private final TransformerRegistry transformerRegistry;
        private final RegistrationContext registrationContext;
        private final DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry;
        protected HostRegistrationStepHandler(final TransformerRegistry transformerRegistry, final RegistrationContext registrationContext, final DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry) {
            this.registrationContext = registrationContext;
            this.transformerRegistry = transformerRegistry;
            this.runtimeIgnoreTransformationRegistry = runtimeIgnoreTransformationRegistry;
        }

        @Override
        public void execute(final OperationContext context, final ModelNode operation) throws OperationFailedException {
            // First lock the domain controller
            context.acquireControllerLock();
            // Check with the controller lock held
            if(domainController.isHostRegistered(registrationContext.hostName)) {
                final String failureDescription = DomainControllerMessages.MESSAGES.slaveAlreadyRegistered(registrationContext.hostName);
                registrationContext.failed(SlaveRegistrationException.ErrorCode.HOST_ALREADY_EXISTS, failureDescription);
                context.getFailureDescription().set(failureDescription);
                context.stepCompleted();
                return;
            }
            // Read the extensions (with recursive true, otherwise the entries are runtime=true - which are going to be ignored for transformation)
            final Resource root = context.readResourceFromRoot(PathAddress.EMPTY_ADDRESS.append(PathElement.pathElement(EXTENSION)), true);
            // Check the mgmt version
            final HostInfo hostInfo = registrationContext.hostInfo;
            final int major = hostInfo.getManagementMajorVersion();
            final int minor = hostInfo.getManagementMinorVersion();
            final int micro = hostInfo.getManagementMicroVersion();
            boolean as711 = (major == 1 && minor == 1);
            if(as711) {
                final OperationFailedException failure = HostControllerMessages.MESSAGES.unsupportedManagementVersionForHost(
                        major, minor, 1, 2);
                registrationContext.failed(failure);
                throw failure;
            }
            // Initialize the transformers
            final TransformationTarget target = TransformationTargetImpl.create(transformerRegistry, ModelVersion.create(major, minor, micro),
                    Collections.<PathAddress, ModelVersion>emptyMap(), hostInfo, TransformationTarget.TransformationTargetType.HOST, registrationContext.runtimeIgnoreTransformation);
            final Transformers transformers = Transformers.Factory.create(target);
            try {
                SlaveChannelAttachments.attachSlaveInfo(handler.getChannel(), registrationContext.hostName, transformers);
            } catch (IOException e) {
                throw new OperationFailedException(e.getLocalizedMessage());
            }
            // Build the extensions list
            final ModelNode extensions = new ModelNode();
            final Resource transformed = transformers.transformRootResource(context, root);
            final Collection<Resource.ResourceEntry> resources = transformed.getChildren(EXTENSION);
            for(final Resource.ResourceEntry entry : resources) {
                extensions.add(entry.getName());
            }
            if(! extensions.isDefined()) {
                throw new OperationFailedException(extensions);
            }
            // Remotely resolve the subsystem versions and create the transformation
            registrationContext.processSubsystems(transformers, extensions);
            // Now run the read-domain model operation
            final ReadMasterDomainModelHandler handler = new ReadMasterDomainModelHandler(hostInfo.getHostName(), transformers, runtimeIgnoreTransformationRegistry);
            context.addStep(READ_DOMAIN_MODEL, handler, OperationContext.Stage.MODEL);
            // Complete
            context.stepCompleted();
        }
    }

    private class RegistrationContext implements ModelController.OperationTransactionControl, ActiveOperation.CompletedCallback<Void> {

        private final TransformerRegistry transformerRegistry;
        private final DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry;
        private final boolean registerOnCompletion;
        private volatile String hostName;
        private volatile HostInfo hostInfo;
        private ManagementRequestContext<RegistrationContext> responseChannel;

        private volatile IOTask<?> task;
        private volatile boolean failed;
        private volatile Transformers transformers;
        private ActiveOperation<Void, RegistrationContext> activeOperation;
        private final AtomicBoolean completed = new AtomicBoolean();
        private volatile DomainControllerRuntimeIgnoreTransformationEntry runtimeIgnoreTransformation;

        private RegistrationContext(TransformerRegistry transformerRegistry) {
            this(transformerRegistry, null, false);
        }

        private RegistrationContext(TransformerRegistry transformerRegistry, DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry) {
            this(transformerRegistry, runtimeIgnoreTransformationRegistry, true);
        }

        private RegistrationContext(TransformerRegistry transformerRegistry,
                                    DomainControllerRuntimeIgnoreTransformationRegistry runtimeIgnoreTransformationRegistry,
                                    boolean registerOnCompletion) {
            this.transformerRegistry = transformerRegistry;
            this.runtimeIgnoreTransformationRegistry = runtimeIgnoreTransformationRegistry;
            this.registerOnCompletion = registerOnCompletion;
        }

        private synchronized void initialize(final String hostName, final ModelNode hostInfo, final ManagementRequestContext<RegistrationContext> responseChannel) {
            this.hostName = hostName;
            this.hostInfo = HostInfo.fromModelNode(hostInfo);
            this.responseChannel = responseChannel;
            this.runtimeIgnoreTransformation = DomainControllerRuntimeIgnoreTransformationEntry.create(this.hostInfo, transformerRegistry.getExtensionRegistry());
            if (runtimeIgnoreTransformationRegistry != null) {
                runtimeIgnoreTransformationRegistry.initializeHost(hostName);
            }
        }

        @Override
        public void completed(Void result) {
            //
        }

        @Override
        public void failed(Exception e) {
            failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getClass().getName() + ":" + e.getMessage());
        }

        @Override
        public void cancelled() {
            //
        }

        @Override
        public void operationPrepared(final ModelController.OperationTransaction transaction, final ModelNode result) {
            if(failed) {
                if (runtimeIgnoreTransformationRegistry != null) {
                    runtimeIgnoreTransformationRegistry.unregisterHost(hostName);
                }
                transaction.rollback();
            } else {
                try {
                    if (registerOnCompletion) {
                        registerHost(transaction, result);
                    } else {
                        // Host just wanted the model; didn't register
                        sendResultToHost(transaction, result);
                    }
                } catch (SlaveRegistrationException e) {
                    failed(e.getErrorCode(), e.getErrorMessage());
                } catch (Exception e) {
                    failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getClass().getName() + ":" + e.getMessage());
                }
                if(failed) {
                    transaction.rollback();
                }
            }
        }

        /**
         *  Process the registration of the slave whose informatin was provided to {@code initialize()}.
         */
        private void processRegistration() {

            // Check for duplicate registrations
            if (domainController.isHostRegistered(hostName)) {
                // asynchronously ping the existing host to validate it's still connected
                // If not, the ping will remove it and a subsequent attempt by the new host will succeed
                // TODO look into doing the ping synchronously
                domainController.pingRemoteHost(hostName);
                // Quick hack -- wait a bit to let async ping detect a re-registration. This can easily be improved
                // via the TODO above
                boolean inter = false; // TODO this is not used
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt(); // TODO why not set inter = true and do this in finally?
                } finally {
                    // Now see if the existing registration has been removed
                    if (domainController.isHostRegistered(hostName)) {
                        failed(SlaveRegistrationException.ErrorCode.HOST_ALREADY_EXISTS, DomainControllerMessages.MESSAGES.slaveAlreadyRegistered(hostName));
                    }
                }
            }

            if (!failed) {
                try {
                    // The domain model is going to be sent as part of the prepared notification
                    final OperationStepHandler handler = new HostRegistrationStepHandler(transformerRegistry, this, runtimeIgnoreTransformationRegistry);
                    ModelNode result = operationExecutor.execute(READ_DOMAIN_MODEL, OperationMessageHandler.logging, this, OperationAttachments.EMPTY, handler);
                    if (FAILED.equals(result.get(OUTCOME).asString())) {
                        failed(SlaveRegistrationException.ErrorCode.UNKNOWN, result.get(FAILURE_DESCRIPTION).asString());
                        return;
                    }
                } catch (Exception e) {
                    failed(e);
                    return;
                }
                // Send a registered notification back
                sendCompletedMessage();
                // Make sure that the host controller gets unregistered when the channel is closed
                responseChannel.getChannel().addCloseHandler(new CloseHandler<Channel>() {
                    @Override
                    public void handleClose(Channel closed, IOException exception) {
                        if (domainController.isHostRegistered(hostName)) {
                            DOMAIN_LOGGER.lostConnectionToRemoteHost(hostName);
                        }
                        domainController.unregisterRemoteHost(hostName, getRemoteConnectionId());
                    }
                });
            }
        }


        /**
         * Create the transformers. This will remotely resolve the subsystem versions.
         *
         * @param extensions the extensions
         * @throws OperationFailedException
         */
        private void processSubsystems(final Transformers transformers, final ModelNode extensions) throws OperationFailedException {
            this.transformers = transformers;
            final ModelNode subsystems = executeBlocking(new IOTask<ModelNode>() {
                @Override
                void sendMessage(FlushableDataOutput output) throws IOException {
                    sendResponse(output, DomainControllerProtocol.PARAM_OK, extensions);
                }
            });
            if(failed) {
                throw new OperationFailedException(new ModelNode("failed to setup transformers"));
            }
            final TransformationTarget target = transformers.getTarget();
            for(final Property subsystem : subsystems.asPropertyList()) {
                final String subsystemName = subsystem.getName();
                final ModelNode version = subsystem.getValue();
                target.addSubsystemVersion(subsystemName, ModelVersion.fromString(version.asString()));
            }
        }

        protected void setSubsystems(final ModelNode resolved, final ManagementRequestContext<RegistrationContext> responseChannel) {
            this.responseChannel = responseChannel;
            completeTask(resolved);
        }

        /**
         * Once the "read-domain-mode" operation is in operationPrepared, send the model back to registering HC.
         * When the model was applied successfully on the client, we process registering the proxy in the domain,
         * otherwise we rollback.
         *
         * @param transaction the model controller tx
         * @param result the prepared result (domain model)
         * @throws SlaveRegistrationException
         */
        void registerHost(final ModelController.OperationTransaction transaction, final ModelNode result) throws SlaveRegistrationException {
            //
            if (sendResultToHost(transaction, result)) return;
            synchronized (this) {
                Long pingPongId = hostInfo.getRemoteConnectionId();
                // Register the slave
                domainController.registerRemoteHost(hostName, handler, transformers, pingPongId, runtimeIgnoreTransformation);
                // Complete registration
                if(! failed) {
                    transaction.commit();
                } else {
                    transaction.rollback();
                    return;
                }
            }
            DOMAIN_LOGGER.registeredRemoteSlaveHost(hostName, hostInfo.getPrettyProductName());
        }

        private boolean sendResultToHost(ModelController.OperationTransaction transaction, final ModelNode result) {
            final Boolean registered = executeBlocking(new IOTask<Boolean>() {
                @Override
                void sendMessage(final FlushableDataOutput output) throws IOException {
                    sendResponse(output, DomainControllerProtocol.PARAM_OK, result);
                }
            });
            if(! registered) {
                transaction.rollback();
                return true;
            }
            return false;
        }

        void completeRegistration(final ManagementRequestContext<RegistrationContext> responseChannel, boolean commit) {
            this.responseChannel = responseChannel;
            failed |= ! commit;
            completeTask(! failed);
        }

        void failed(SlaveRegistrationException.ErrorCode errorCode, String message) {
            failed(errorCode.getCode(), message);
        }

        void failed(byte errorCode, String message) {
            if(completed.compareAndSet(false, true)) {
                failed = true;
                final IOTask<?> task = this.task;
                if(task != null) {
                    task.setFailed();
                }
                try {
                    sendFailedResponse(responseChannel, errorCode, message);
                } catch (IOException e) {
                    ProtocolLogger.ROOT_LOGGER.debugf(e, "failed to process message");
                }
                activeOperation.getResultHandler().done(null);
            }
        }

        void sendCompletedMessage() {
            if(completed.compareAndSet(false, true)) {
                try {
                    sendResponse(responseChannel, DomainControllerProtocol.PARAM_OK, null);
                } catch (IOException e) {
                    ProtocolLogger.ROOT_LOGGER.debugf(e, "failed to process message");
                }
                activeOperation.getResultHandler().done(null);
            }
        }

        Long getRemoteConnectionId() {
            return hostInfo.getRemoteConnectionId();
        }

        protected boolean completeTask(Object result) {
            synchronized (this) {
                if(failed) {
                    return false;
                }
                if(task != null) {
                    return task.completeStep(result);
                }
            }
            return false;
        }

        /**
         * Execute a task and wait for the response.
         *
         * @param task the task to execute
         * @param <T> the response type
         * @return the result
         */
        protected <T> T executeBlocking(final IOTask<T> task) {
            synchronized (this) {
                this.task = task;
                try {
                    final ManagementResponseHeader header = ManagementResponseHeader.create(responseChannel.getRequestHeader());
                    final FlushableDataOutput output = responseChannel.writeMessage(header);
                    try {
                        task.sendMessage(output);
                    } catch (IOException e) {
                        failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getMessage());
                        throw new IllegalStateException(e);
                    } finally {
                        StreamUtils.safeClose(output);
                    }
                } catch (IOException e) {
                    failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getMessage());
                    throw new IllegalStateException(e);
                }
            }
            try {
                return task.get();
            } catch (InterruptedException e) {
                failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getMessage());
                throw new IllegalStateException(e);
            } catch (ExecutionException e) {
                failed(SlaveRegistrationException.ErrorCode.UNKNOWN, e.getMessage());
                throw new IllegalStateException(e);
            }
        }

    }

    abstract static class IOTask<T> extends AsyncFutureTask<T> {

        IOTask() {
            super(null);
        }

        abstract void sendMessage(final FlushableDataOutput output) throws IOException;

        @SuppressWarnings("unchecked")
        boolean completeStep(Object result) {
            return setResult((T) result);
        }

        boolean setFailed() {
            return setFailed(null);
        }
    }

    /**
     * Send a operation response.
     *
     * @param context the request context
     * @param responseType the response type
     * @param response the operation response
     * @throws IOException for any error
     */
    static void sendResponse(final ManagementRequestContext<RegistrationContext> context, final byte responseType, final ModelNode response) throws IOException {
        final ManagementResponseHeader header = ManagementResponseHeader.create(context.getRequestHeader());
        final FlushableDataOutput output = context.writeMessage(header);
        try {
            sendResponse(output, responseType, response);
        } finally {
            StreamUtils.safeClose(output);
        }
    }

    static void sendResponse(final FlushableDataOutput output, final byte responseType, final ModelNode response) throws IOException {
        // response type
        output.writeByte(responseType);
        if(response != null) {
            // operation result
            response.writeExternal(output);
        }
        // response end
        output.writeByte(ManagementProtocol.RESPONSE_END);
        output.close();
    }

    /**
     * Send a failed operation response.
     *
     * @param context the request context
     * @param errorCode the error code
     * @param message the operation message
     * @throws IOException for any error
     */
    static void sendFailedResponse(final ManagementRequestContext<RegistrationContext> context, final byte errorCode, final String message) throws IOException {
        final ManagementResponseHeader header = ManagementResponseHeader.create(context.getRequestHeader());
        final FlushableDataOutput output = context.writeMessage(header);
        try {
            // This is an error
            output.writeByte(DomainControllerProtocol.PARAM_ERROR);
            // send error code
            output.writeByte(errorCode);
            // error message
            output.writeUTF(message);
            // response end
            output.writeByte(ManagementProtocol.RESPONSE_END);
            output.close();
        } finally {
            StreamUtils.safeClose(output);
        }
    }

}
