/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/.

 *

 *    Copyright 2014-2018, 2022 (c) Fraunhofer IOSB (Author: Julius Pfrommer)

 *    Copyright 2016-2017 (c) Florian Palm

 *    Copyright 2015 (c) Chris Iatrou

 *    Copyright 2015-2016 (c) Sten Grüner

 *    Copyright 2015-2016 (c) Oleksiy Vasylyev

 *    Copyright 2017 (c) Stefan Profanter, fortiss GmbH

 *    Copyright 2018 (c) Ari Breitkreuz, fortiss GmbH

 *    Copyright 2017 (c) Mattias Bornhager

 *    Copyright 2017 (c) Henrik Norrman

 *    Copyright 2017-2018 (c) Thomas Stalder, Blue Time Concept SA

 *    Copyright 2018 (c) Fabian Arndt, Root-Core

 *    Copyright 2017-2019 (c) HMS Industrial Networks AB (Author: Jonas Green)

 */

#include "ua_server_internal.h"

#include "ua_services.h"

#include "ua_subscription.h"

#ifdef UA_ENABLE_SUBSCRIPTIONS /* conditional compilation */

static void

setSubscriptionSettings(UA_Server *server, UA_Subscription *subscription,

                        UA_Double requestedPublishingInterval,

                        UA_UInt32 requestedLifetimeCount,

                        UA_UInt32 requestedMaxKeepAliveCount,

                        UA_UInt32 maxNotificationsPerPublish,

                        UA_Byte priority) {

    UA_LOCK_ASSERT(&server->serviceMutex);

    /* re-parameterize the subscription */

    UA_BOUNDEDVALUE_SETWBOUNDS(server->config.publishingIntervalLimits,

                               requestedPublishingInterval,

                               subscription->publishingInterval);

    /* check for nan*/

    if(requestedPublishingInterval != requestedPublishingInterval)

        subscription->publishingInterval = server->config.publishingIntervalLimits.min;

    UA_BOUNDEDVALUE_SETWBOUNDS(server->config.keepAliveCountLimits,

                               requestedMaxKeepAliveCount, subscription->maxKeepAliveCount);

    UA_BOUNDEDVALUE_SETWBOUNDS(server->config.lifeTimeCountLimits,

                               requestedLifetimeCount, subscription->lifeTimeCount);

    if(subscription->lifeTimeCount < 3 * subscription->maxKeepAliveCount)

        subscription->lifeTimeCount = 3 * subscription->maxKeepAliveCount;

    subscription->notificationsPerPublish = maxNotificationsPerPublish;

    if(maxNotificationsPerPublish == 0 ||

       maxNotificationsPerPublish > server->config.maxNotificationsPerPublish)

        subscription->notificationsPerPublish = server->config.maxNotificationsPerPublish;

    subscription->priority = priority;

}

static void

notifySubscription(UA_Server *server, UA_Subscription *sub,

                   UA_ApplicationNotificationType type) {

    if(!server->config.subscriptionNotificationCallback &&

       !server->config.globalNotificationCallback)

        return;

    static UA_THREAD_LOCAL UA_KeyValuePair createSubData[8] = {

        {{0, UA_STRING_STATIC("session-id")}, {0}},

        {{0, UA_STRING_STATIC("subscription-id")}, {0}},

        {{0, UA_STRING_STATIC("publishing-interval")}, {0}},

        {{0, UA_STRING_STATIC("lifetime-count")}, {0}},

        {{0, UA_STRING_STATIC("max-keepalive-count")}, {0}},

        {{0, UA_STRING_STATIC("max-notifications-per-publish")}, {0}},

        {{0, UA_STRING_STATIC("priority")}, {0}},

        {{0, UA_STRING_STATIC("publishing-enabled")}, {0}}

    };

    UA_KeyValueMap createSubMap = {8, createSubData};

    UA_NodeId sessionId = (sub->session) ? sub->session->sessionId : UA_NODEID_NULL;

    UA_Boolean enabled = (sub->state = UA_SUBSCRIPTIONSTATE_ENABLED);

    UA_Variant_setScalar(&createSubData[0].value, &sessionId,

                         &UA_TYPES[UA_TYPES_NODEID]);

    UA_Variant_setScalar(&createSubData[1].value, &sub->subscriptionId,

                         &UA_TYPES[UA_TYPES_UINT32]);

    UA_Variant_setScalar(&createSubData[2].value, &sub->publishingInterval,

                         &UA_TYPES[UA_TYPES_DOUBLE]);

    UA_Variant_setScalar(&createSubData[3].value, &sub->lifeTimeCount,

                         &UA_TYPES[UA_TYPES_UINT32]);

    UA_Variant_setScalar(&createSubData[4].value, &sub->maxKeepAliveCount,

                         &UA_TYPES[UA_TYPES_UINT32]);

    UA_Variant_setScalar(&createSubData[5].value, &sub->notificationsPerPublish,

                         &UA_TYPES[UA_TYPES_UINT32]);

    UA_Variant_setScalar(&createSubData[6].value, &sub->priority,

                         &UA_TYPES[UA_TYPES_BYTE]);

    UA_Variant_setScalar(&createSubData[7].value, &enabled,

                         &UA_TYPES[UA_TYPES_BOOLEAN]);

    if(server->config.subscriptionNotificationCallback)

        server->config.subscriptionNotificationCallback(server, type, createSubMap);

    if(server->config.globalNotificationCallback)

        server->config.globalNotificationCallback(server, type, createSubMap);

}

UA_Boolean

Service_CreateSubscription(UA_Server *server, UA_Session *session,

                           const UA_CreateSubscriptionRequest *request,

                           UA_CreateSubscriptionResponse *response) {

    UA_LOCK_ASSERT(&server->serviceMutex);

    /* Check limits for the number of subscriptions */

    if(((server->config.maxSubscriptions != 0) &&

        (server->subscriptionsSize >= server->config.maxSubscriptions)) ||

       ((server->config.maxSubscriptionsPerSession != 0) &&

        (session->subscriptionsSize >= server->config.maxSubscriptionsPerSession))) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADTOOMANYSUBSCRIPTIONS;

        return true;

    }

    /* Create the subscription */

    UA_Subscription *sub = UA_Subscription_new();

    if(!sub) {

        UA_LOG_DEBUG_SESSION(server->config.logging, session,

                             "Processing CreateSubscriptionRequest failed");

        response->responseHeader.serviceResult = UA_STATUSCODE_BADOUTOFMEMORY;

        return true;

    }

    /* Set the subscription parameters */

    setSubscriptionSettings(server, sub, request->requestedPublishingInterval,

                            request->requestedLifetimeCount,

                            request->requestedMaxKeepAliveCount,

                            request->maxNotificationsPerPublish, request->priority);

    sub->subscriptionId = ++server->lastSubscriptionId;  /* Assign the SubscriptionId */

    /* Register the subscription in the server */

    LIST_INSERT_HEAD(&server->subscriptions, sub, serverListEntry);

    server->subscriptionsSize++;

    /* Update the server statistics */

    server->serverDiagnosticsSummary.currentSubscriptionCount++;

    server->serverDiagnosticsSummary.cumulatedSubscriptionCount++;

    /* Attach the Subscription to the session */

    UA_Session_attachSubscription(session, sub);

    /* Create representation in the Session object */

#ifdef UA_ENABLE_DIAGNOSTICS

    createSubscriptionObject(server, session, sub);

#endif

    /* Set the subscription state. This also registers the callback.

     * Note that also a disabled subscription publishes keepalives. */

    UA_SubscriptionState sState = (request->publishingEnabled) ?

        UA_SUBSCRIPTIONSTATE_ENABLED : UA_SUBSCRIPTIONSTATE_ENABLED_NOPUBLISH;

    UA_StatusCode res = Subscription_setState(server, sub, sState);

    if(res != UA_STATUSCODE_GOOD) {

        UA_LOG_DEBUG_SESSION(server->config.logging, sub->session,

                             "Subscription %" PRIu32 " | Could not register "

                             "publish callback with error code %s",

                             sub->subscriptionId, UA_StatusCode_name(res));

        response->responseHeader.serviceResult = res;

        UA_Subscription_delete(server, sub);

        return true;

    }

    UA_LOG_INFO_SUBSCRIPTION(server->config.logging, sub,

                             "Subscription created (Publishing interval %.2fms, "

                             "max %lu notifications per publish)",

                             sub->publishingInterval,

                             (long unsigned)sub->notificationsPerPublish);

    /* Notify the application */

    notifySubscription(server, sub,

                       UA_APPLICATIONNOTIFICATIONTYPE_SUBSCRIPTION_CREATED);

    /* Prepare the response */

    response->subscriptionId = sub->subscriptionId;

    response->revisedPublishingInterval = sub->publishingInterval;

    response->revisedLifetimeCount = sub->lifeTimeCount;

    response->revisedMaxKeepAliveCount = sub->maxKeepAliveCount;

    return true;

}

UA_Boolean

Service_ModifySubscription(UA_Server *server, UA_Session *session,

                           const UA_ModifySubscriptionRequest *request,

                           UA_ModifySubscriptionResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing ModifySubscriptionRequest");

    UA_LOCK_ASSERT(&server->serviceMutex);

    UA_Subscription *sub = UA_Session_getSubscriptionById(session, request->subscriptionId);

    if(!sub) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

        return true;

    }

    /* Store the old publishing interval */

    UA_Double oldPublishingInterval = sub->publishingInterval;

    UA_Byte oldPriority = sub->priority;

    /* Change the Subscription settings */

    setSubscriptionSettings(server, sub, request->requestedPublishingInterval,

                            request->requestedLifetimeCount,

                            request->requestedMaxKeepAliveCount,

                            request->maxNotificationsPerPublish, request->priority);

    /* Reset the subscription lifetime */

    Subscription_resetLifetime(sub);

    /* The publish interval has changed */

    if(sub->publishingInterval != oldPublishingInterval) {

        /* Change the repeated callback to the new interval. This cannot fail as

         * memory is reused. */

        if(sub->publishCallbackId > 0)

            changeRepeatedCallbackInterval(server, sub->publishCallbackId,

                                           sub->publishingInterval);

        /* For each MonitoredItem check if it was/shall be attached to the

         * publish interval. This ensures that we have less cyclic callbacks

         * registered and that the notifications are fresh. */

        UA_MonitoredItem *mon;

        LIST_FOREACH(mon, &sub->monitoredItems, listEntry) {

            if(mon->parameters.samplingInterval == sub->publishingInterval ||

               mon->parameters.samplingInterval == oldPublishingInterval) {

                UA_MonitoredItem_unregisterSampling(server, mon);

                UA_MonitoredItem_registerSampling(server, mon);

            }

        }

    }

    /* If the priority has changed, re-enter the subscription to the

     * priority-ordered queue in the session. */

    if(oldPriority != sub->priority) {

        UA_Session_detachSubscription(server, session, sub, false);

        UA_Session_attachSubscription(session, sub);

    }

    /* Notify the application */

    notifySubscription(server, sub,

                       UA_APPLICATIONNOTIFICATIONTYPE_SUBSCRIPTION_MODIFIED);

    /* Set the response */

    response->revisedPublishingInterval = sub->publishingInterval;

    response->revisedLifetimeCount = sub->lifeTimeCount;

    response->revisedMaxKeepAliveCount = sub->maxKeepAliveCount;

    /* Update the diagnostics statistics */

#ifdef UA_ENABLE_DIAGNOSTICS

    sub->modifyCount++;

#endif

    return true;

}

static void

Operation_SetPublishingMode(UA_Server *server, UA_Session *session,

                            const UA_Boolean *publishingEnabled,

                            const UA_UInt32 *subscriptionId,

                            UA_StatusCode *result) {

    UA_LOCK_ASSERT(&server->serviceMutex);

    UA_Subscription *sub = UA_Session_getSubscriptionById(session, *subscriptionId);

    if(!sub) {

        *result = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

        return;

    }

    /* Enable/disable */

    UA_SubscriptionState sState = (*publishingEnabled) ?

        UA_SUBSCRIPTIONSTATE_ENABLED : UA_SUBSCRIPTIONSTATE_ENABLED_NOPUBLISH;

    *result = Subscription_setState(server, sub, sState);

    /* Reset the lifetime counter */

    Subscription_resetLifetime(sub);

    /* Notify the application */

    notifySubscription(server, sub,

                       UA_APPLICATIONNOTIFICATIONTYPE_SUBSCRIPTION_PUBLISHINGMODE);

}

UA_Boolean

Service_SetPublishingMode(UA_Server *server, UA_Session *session,

                          const UA_SetPublishingModeRequest *request,

                          UA_SetPublishingModeResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing SetPublishingModeRequest");

    UA_LOCK_ASSERT(&server->serviceMutex);

    UA_Boolean publishingEnabled = request->publishingEnabled; /* request is const */

    response->responseHeader.serviceResult =

        allocProcessServiceOperations(server, session,

                                      (UA_ServiceOperation)Operation_SetPublishingMode,

                                      &publishingEnabled, &request->subscriptionIdsSize,

                                      &UA_TYPES[UA_TYPES_UINT32], &response->resultsSize,

                                      &UA_TYPES[UA_TYPES_STATUSCODE]);

    return true;

}

UA_Boolean

Service_Publish(UA_Server *server, UA_Session *session,

                const UA_PublishRequest *request,

                UA_PublishResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing PublishRequest with RequestId %u",

                         server->asyncManager.currentRequestId);

    UA_LOCK_ASSERT(&server->serviceMutex);

    /* Return an error if the session has no subscription */

    if(TAILQ_EMPTY(&session->subscriptions)) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADNOSUBSCRIPTION;

        return true;

    }

    /* Handle too many subscriptions to free resources before trying to allocate

     * resources for the new publish request. If the limit has been reached the

     * oldest publish request are returned with an error message. */

    UA_Session_ensurePublishQueueSpace(server, session);

    /* Allocate the response to store it in the retransmission queue */

    UA_PublishResponseEntry *entry = (UA_PublishResponseEntry *)

        UA_malloc(sizeof(UA_PublishResponseEntry));

    if(!entry) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADOUTOFMEMORY;

        return true;

    }

    /* Prepare the response */

    UA_PublishResponse *entry_response = &entry->response;

    UA_PublishResponse_init(entry_response);

    /* Allocate the results array to acknowledge the acknowledge */

    if(request->subscriptionAcknowledgementsSize > 0) {

        entry_response->results = (UA_StatusCode *)

            UA_Array_new(request->subscriptionAcknowledgementsSize,

                         &UA_TYPES[UA_TYPES_STATUSCODE]);

        if(!entry_response->results) {

            UA_free(entry);

            response->responseHeader.serviceResult = UA_STATUSCODE_BADOUTOFMEMORY;

            return true;

        }

        entry_response->resultsSize = request->subscriptionAcknowledgementsSize;

    }

    /* <--- Async response from here on ---> */

    entry->requestId = server->asyncManager.currentRequestId;

    entry_response->responseHeader.requestHandle = request->requestHeader.requestHandle;

    /* Delete Acknowledged Subscription Messages */

    for(size_t i = 0; i < request->subscriptionAcknowledgementsSize; ++i) {

        UA_SubscriptionAcknowledgement *ack = &request->subscriptionAcknowledgements[i];

        UA_Subscription *sub = UA_Session_getSubscriptionById(session, ack->subscriptionId);

        if(!sub) {

            entry_response->results[i] = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

            UA_LOG_DEBUG_SESSION(server->config.logging, session,

                                 "Cannot process acknowledgements subscription %u" PRIu32,

                                 ack->subscriptionId);

            continue;

        }

        /* Remove the acked transmission from the retransmission queue */

        entry_response->results[i] =

            UA_Subscription_removeRetransmissionMessage(sub, ack->sequenceNumber);

    }

    /* Set the maxTime if a timeout hint is defined */

    entry->maxTime = UA_INT64_MAX;

    if(request->requestHeader.timeoutHint > 0) {

        UA_EventLoop *el = server->config.eventLoop;

        entry->maxTime = el->dateTime_nowMonotonic(el) +

            (request->requestHeader.timeoutHint * UA_DATETIME_MSEC);

    }

    /* Queue the publish response. It will be dequeued in a repeated publish

     * callback. This can also be triggered right now for a late

     * subscription. */

    UA_Session_queuePublishReq(session, entry, false);

    UA_LOG_DEBUG_SESSION(server->config.logging, session, "Queued a publication message");

    /* If there are late subscriptions, the new publish request is used to

     * answer them immediately. Late subscriptions with higher priority are

     * considered earlier. However, a single subscription that generates many

     * notifications must not "starve" other late subscriptions. Hence we move

     * it to the end of the queue for the subscriptions of that priority. */

    UA_Subscription *late, *late_tmp;

    TAILQ_FOREACH_SAFE(late, &session->subscriptions, sessionListEntry, late_tmp) {

        /* Skip non-late subscriptions */

        if(!late->late)

            continue;

        /* Call publish on the late subscription */

        UA_LOG_DEBUG_SUBSCRIPTION(server->config.logging, late,

                                  "Send PublishResponse on a late subscription");

        UA_Subscription_publish(server, late);

        /* Skip re-insert if the subscription was deleted or deactivated during

         * _publish */

        if(late->state >= UA_SUBSCRIPTIONSTATE_ENABLED_NOPUBLISH) {

            /* Find the first element with smaller priority and insert before

             * that. If there is none, insert at the end of the queue. */

            UA_Subscription *after = TAILQ_NEXT(late, sessionListEntry);

            while(after && after->priority >= late->priority)

                after = TAILQ_NEXT(after, sessionListEntry);

            TAILQ_REMOVE(&session->subscriptions, late, sessionListEntry);

            if(after)

                TAILQ_INSERT_BEFORE(after, late, sessionListEntry);

            else

                TAILQ_INSERT_TAIL(&session->subscriptions, late, sessionListEntry);

        }

        /* Responses left in the queue? */

        if(session->responseQueueSize == 0)

            break;

    }

    return false;

}

static void

Operation_DeleteSubscription(UA_Server *server, UA_Session *session, void *_,

                             const UA_UInt32 *subscriptionId, UA_StatusCode *result) {

    /* Find the Subscription */

    UA_Subscription *sub = UA_Session_getSubscriptionById(session, *subscriptionId);

    if(!sub) {

        *result = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

        UA_LOG_DEBUG_SESSION(server->config.logging, session,

                             "Deleting Subscription with Id %" PRIu32

                             " failed with error code %s",

                             *subscriptionId, UA_StatusCode_name(*result));

        return;

    }

    /* Notify the application */

    notifySubscription(server, sub,

                       UA_APPLICATIONNOTIFICATIONTYPE_SUBSCRIPTION_DELETED);

    /* Delete the Subscription */

    UA_Subscription_delete(server, sub);

    *result = UA_STATUSCODE_GOOD;

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Subscription %" PRIu32 " | Subscription deleted",

                         *subscriptionId);

}

UA_Boolean

Service_DeleteSubscriptions(UA_Server *server, UA_Session *session,

                            const UA_DeleteSubscriptionsRequest *request,

                            UA_DeleteSubscriptionsResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing DeleteSubscriptionsRequest");

    UA_LOCK_ASSERT(&server->serviceMutex);

    response->responseHeader.serviceResult =

        allocProcessServiceOperations(server, session,

                                      (UA_ServiceOperation)Operation_DeleteSubscription,

                                      NULL, &request->subscriptionIdsSize,

                                      &UA_TYPES[UA_TYPES_UINT32], &response->resultsSize,

                                      &UA_TYPES[UA_TYPES_STATUSCODE]);

    return true;

}

UA_Boolean

Service_Republish(UA_Server *server, UA_Session *session,

                  const UA_RepublishRequest *request,

                  UA_RepublishResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing RepublishRequest");

    UA_LOCK_ASSERT(&server->serviceMutex);

    /* Get the subscription */

    UA_Subscription *sub = UA_Session_getSubscriptionById(session, request->subscriptionId);

    if(!sub) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

        return true;

    }

    /* Reset the lifetime counter */

    Subscription_resetLifetime(sub);

    /* Update the subscription statistics */

#ifdef UA_ENABLE_DIAGNOSTICS

    sub->republishRequestCount++;

#endif

    /* Find the notification in the retransmission queue  */

    UA_NotificationMessageEntry *entry;

    TAILQ_FOREACH(entry, &sub->retransmissionQueue, listEntry) {

        if(entry->message.sequenceNumber == request->retransmitSequenceNumber)

            break;

    }

    if(!entry) {

        response->responseHeader.serviceResult = UA_STATUSCODE_BADMESSAGENOTAVAILABLE;

        return true;

    }

    response->responseHeader.serviceResult =

        UA_NotificationMessage_copy(&entry->message, &response->notificationMessage);

    /* Update the subscription statistics for the case where we return a message */

#ifdef UA_ENABLE_DIAGNOSTICS

    sub->republishMessageCount++;

#endif

    return true;

}

static UA_StatusCode

setTransferredSequenceNumbers(const UA_Subscription *sub, UA_TransferResult *result) {

    /* Allocate memory */

    result->availableSequenceNumbers = (UA_UInt32*)

        UA_Array_new(sub->retransmissionQueueSize, &UA_TYPES[UA_TYPES_UINT32]);

    if(!result->availableSequenceNumbers)

        return UA_STATUSCODE_BADOUTOFMEMORY;

    result->availableSequenceNumbersSize = sub->retransmissionQueueSize;

    /* Copy over the sequence numbers */

    UA_NotificationMessageEntry *entry;

    size_t i = 0;

    TAILQ_FOREACH(entry, &sub->retransmissionQueue, listEntry) {

        result->availableSequenceNumbers[i] = entry->message.sequenceNumber;

        i++;

    }

    UA_assert(i == result->availableSequenceNumbersSize);

    return UA_STATUSCODE_GOOD;

}

static void

Operation_TransferSubscription(UA_Server *server, UA_Session *session,

                               const UA_Boolean *sendInitialValues,

                               const UA_UInt32 *subscriptionId,

                               UA_TransferResult *result) {

    UA_LOCK_ASSERT(&server->serviceMutex);

    /* Get the subscription. This requires a server-wide lookup instead of the

     * usual session-wide lookup. */

    UA_Subscription *sub = getSubscriptionById(server, *subscriptionId);

    if(!sub) {

        result->statusCode = UA_STATUSCODE_BADSUBSCRIPTIONIDINVALID;

        return;

    }

    /* Update the diagnostics statistics */

#ifdef UA_ENABLE_DIAGNOSTICS

    sub->transferRequestCount++;

#endif

    /* Is this the same session? Return the sequence numbers and do nothing else. */

    UA_Session *oldSession = sub->session;

    if(oldSession == session) {

        result->statusCode = setTransferredSequenceNumbers(sub, result);

#ifdef UA_ENABLE_DIAGNOSTICS

        sub->transferredToSameClientCount++;

#endif

        return;

    }

    /* Check with AccessControl if the transfer is allowed */

    if(server->config.accessControl.allowTransferSubscription) {

        if(!server->config.accessControl.

           allowTransferSubscription(server, &server->config.accessControl,

                                     oldSession ? &oldSession->sessionId : NULL,

                                     oldSession ? oldSession->context : NULL,

                                     &session->sessionId, session->context)) {

            result->statusCode = UA_STATUSCODE_BADUSERACCESSDENIED;

            return;

        }

    } else {

        result->statusCode = UA_STATUSCODE_BADUSERACCESSDENIED;

        return;

    }

    /* Check limits for the number of subscriptions for this Session */

    if((server->config.maxSubscriptionsPerSession != 0) &&

       (session->subscriptionsSize >= server->config.maxSubscriptionsPerSession)) {

        result->statusCode = UA_STATUSCODE_BADTOOMANYSUBSCRIPTIONS;

        return;

    }

    /* Allocate memory for the new subscription */

    UA_Subscription *newSub = (UA_Subscription*)UA_malloc(sizeof(UA_Subscription));

    if(!newSub) {

        result->statusCode = UA_STATUSCODE_BADOUTOFMEMORY;

        return;

    }

    /* Set the available sequence numbers */

    result->statusCode = setTransferredSequenceNumbers(sub, result);

    if(result->statusCode != UA_STATUSCODE_GOOD) {

        UA_free(newSub);

        return;

    }

    /* Create an identical copy of the Subscription struct. The original

     * subscription remains in place until a StatusChange notification has been

     * sent. The elements for lists and queues are moved over manually to ensure

     * that all backpointers are set correctly. */

    memcpy(newSub, sub, sizeof(UA_Subscription));

    /* Set to the same state as the original subscription */

    newSub->publishCallbackId = 0;

    result->statusCode = Subscription_setState(server, newSub, sub->state);

    if(result->statusCode != UA_STATUSCODE_GOOD) {

        UA_Array_delete(result->availableSequenceNumbers,

                        sub->retransmissionQueueSize, &UA_TYPES[UA_TYPES_UINT32]);

        result->availableSequenceNumbers = NULL;

        result->availableSequenceNumbersSize = 0;

        UA_free(newSub);

        return;

    }

    /* <-- The point of no return --> */

    /* Move over the MonitoredItems and adjust the backpointers */

    LIST_INIT(&newSub->monitoredItems);

    UA_MonitoredItem *mon, *mon_tmp;

    LIST_FOREACH_SAFE(mon, &sub->monitoredItems, listEntry, mon_tmp) {

        LIST_REMOVE(mon, listEntry);

        mon->subscription = newSub;

        LIST_INSERT_HEAD(&newSub->monitoredItems, mon, listEntry);

    }

    sub->monitoredItemsSize = 0;

    /* Move over the notification queue */

    TAILQ_INIT(&newSub->notificationQueue);

    UA_Notification *nn, *nn_tmp;

    TAILQ_FOREACH_SAFE(nn, &sub->notificationQueue, subEntry, nn_tmp) {

        TAILQ_REMOVE(&sub->notificationQueue, nn, subEntry);

        TAILQ_INSERT_TAIL(&newSub->notificationQueue, nn, subEntry);

    }

    sub->notificationQueueSize = 0;

    sub->dataChangeNotifications = 0;

    sub->eventNotifications = 0;

    TAILQ_INIT(&newSub->retransmissionQueue);

    UA_NotificationMessageEntry *nme, *nme_tmp;

    TAILQ_FOREACH_SAFE(nme, &sub->retransmissionQueue, listEntry, nme_tmp) {

        TAILQ_REMOVE(&sub->retransmissionQueue, nme, listEntry);

        TAILQ_INSERT_TAIL(&newSub->retransmissionQueue, nme, listEntry);

        if(oldSession)

            oldSession->totalRetransmissionQueueSize -= 1;

        sub->retransmissionQueueSize -= 1;

    }

    UA_assert(sub->retransmissionQueueSize == 0);

    sub->retransmissionQueueSize = 0;

    /* Add to the server */

    UA_assert(newSub->subscriptionId == sub->subscriptionId);

    LIST_INSERT_HEAD(&server->subscriptions, newSub, serverListEntry);

    server->subscriptionsSize++;

    /* Attach to the session */

    UA_Session_attachSubscription(session, newSub);

    /* Notify the application */

    notifySubscription(server, newSub,

                       UA_APPLICATIONNOTIFICATIONTYPE_SUBSCRIPTION_TRANSFERRED);

    UA_LOG_INFO_SUBSCRIPTION(server->config.logging, newSub,

                             "Transferred to this Session");

    /* Set StatusChange in the original subscription and force publish. This

     * also removes the Subscription, even if there was no PublishResponse

     * queued to send a StatusChangeNotification. */

    sub->statusChange = UA_STATUSCODE_GOODSUBSCRIPTIONTRANSFERRED;

    UA_Subscription_publish(server, sub);

    /* Re-create notifications with the current values for the new subscription */

    if(*sendInitialValues)

        UA_Subscription_resendData(server, newSub);

    /* Do not update the statistics for the number of Subscriptions here. The

     * fact that we duplicate the subscription and move over the content is just

     * an implementtion detail.

     * server->serverDiagnosticsSummary.currentSubscriptionCount++;

     * server->serverDiagnosticsSummary.cumulatedSubscriptionCount++;

     *

     * Update the diagnostics statistics: */

#ifdef UA_ENABLE_DIAGNOSTICS

    if(oldSession &&

       UA_equal(&oldSession->clientDescription, &session->clientDescription,

                &UA_TYPES[UA_TYPES_APPLICATIONDESCRIPTION]))

        sub->transferredToSameClientCount++;

    else

        sub->transferredToAltClientCount++;

#endif

}

UA_Boolean

Service_TransferSubscriptions(UA_Server *server, UA_Session *session,

                              const UA_TransferSubscriptionsRequest *request,

                              UA_TransferSubscriptionsResponse *response) {

    UA_LOG_DEBUG_SESSION(server->config.logging, session,

                         "Processing TransferSubscriptionsRequest");

    UA_LOCK_ASSERT(&server->serviceMutex);

    response->responseHeader.serviceResult =

        allocProcessServiceOperations(server, session,

                                      (UA_ServiceOperation)Operation_TransferSubscription,

                                      &request->sendInitialValues,

                                      &request->subscriptionIdsSize,

                                      &UA_TYPES[UA_TYPES_UINT32],

                                      &response->resultsSize,

                                      &UA_TYPES[UA_TYPES_TRANSFERRESULT]);

    return true;

}

#endif /* UA_ENABLE_SUBSCRIPTIONS */