Application.cc

/*
 * Application.cc
 *
 *  Created on: Jun 10, 2016
 *      Author: Martin Hierholzer
 */

#include <exception>
#include <fstream>
#include <string>
#include <thread>

#include <boost/fusion/container/map.hpp>

#include <ChimeraTK/BackendFactory.h>

#include "Application.h"
#include "ApplicationModule.h"
#include "ArrayAccessor.h"
#include "ConstantAccessor.h"
#include "ConsumingFanOut.h"
#include "DebugPrintAccessorDecorator.h"
#include "DeviceModule.h"
#include "FeedingFanOut.h"
#include "ScalarAccessor.h"
#include "TestableModeAccessorDecorator.h"
#include "ThreadedFanOut.h"
#include "TriggerFanOut.h"
#include "VariableNetworkGraphDumpingVisitor.h"
#include "VariableNetworkNode.h"
#include "Visitor.h"
#include "XMLGeneratorVisitor.h"

using namespace ChimeraTK;

std::mutex Application::testableMode_mutex;

/*********************************************************************************************************************/

Application::Application(const std::string &name)
    : ApplicationBase(name), EntityOwner(name, "") {
  // check if the application name has been set
  if (applicationName == "") {
    shutdown();
    throw ChimeraTK::logic_error(
        "Error: An instance of Application must have its applicationName set.");
  }
  // check if application name contains illegal characters
  std::string legalChars =
      "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_";
  bool nameContainsIllegalChars =
      name.find_first_not_of(legalChars) != std::string::npos;
  if (nameContainsIllegalChars) {
    shutdown();
    throw ChimeraTK::logic_error("Error: The application name may only contain "
                                 "alphanumeric characters and underscores.");
  }
}

/*********************************************************************************************************************/

void Application::initialise() {
  // call the user-defined defineConnections() function which describes the
  // structure of the application
  defineConnections();

  // connect any unconnected accessors with constant values
  processUnconnectedNodes();

  // realise the connections between variable accessors as described in the
  // initialise() function
  makeConnections();
}

/*********************************************************************************************************************/

/** Functor class to create a constant for otherwise unconnected variables,
 * suitable for boost::fusion::for_each(). */
namespace {
struct CreateConstantForUnconnectedVar {
  /// @todo test unconnected variables for all types!
  CreateConstantForUnconnectedVar(const std::type_info &typeInfo,
                                  bool makeFeeder, size_t length)
      : _typeInfo(typeInfo), _makeFeeder(makeFeeder), _length(length) {}

  template <typename PAIR> void operator()(PAIR &) const {
    if (typeid(typename PAIR::first_type) != _typeInfo)
      return;
    theNode = VariableNetworkNode::makeConstant<typename PAIR::first_type>(
        _makeFeeder, typename PAIR::first_type(), _length);
    done = true;
  }

  const std::type_info &_typeInfo;
  bool _makeFeeder;
  size_t _length;
  mutable bool done{false};
  mutable VariableNetworkNode theNode;
};
} // namespace

/*********************************************************************************************************************/

void Application::processUnconnectedNodes() {
  for (auto &module : getSubmoduleListRecursive()) {
    for (auto &accessor : module->getAccessorList()) {
      if (!accessor.hasOwner()) {
        if (enableUnconnectedVariablesWarning) {
          std::cerr
              << "*** Warning: Variable '" << accessor.getQualifiedName()
              << "' is not connected. " // LCOV_EXCL_LINE
                 "Reading will always result in 0, writing will be ignored."
              << std::endl; // LCOV_EXCL_LINE
        }
        networkList.emplace_back();
        networkList.back().addNode(accessor);

        bool makeFeeder = !(networkList.back().hasFeedingNode());
        size_t length = accessor.getNumberOfElements();
        auto callable = CreateConstantForUnconnectedVar(accessor.getValueType(),
                                                        makeFeeder, length);
        boost::fusion::for_each(ChimeraTK::userTypeMap(), std::ref(callable));
        assert(callable.done);
        constantList.emplace_back(callable.theNode);
        networkList.back().addNode(constantList.back());
      }
    }
  }
}

/*********************************************************************************************************************/

void Application::checkConnections() {
  // check all networks for validity
  for (auto &network : networkList) {
    network.check();
  }

  // check if all accessors are connected
  // note: this in principle cannot happen, since processUnconnectedNodes() is
  // called before
  for (auto &module : getSubmoduleListRecursive()) {
    for (auto &accessor : module->getAccessorList()) {
      if (!accessor.hasOwner()) {
        throw ChimeraTK::logic_error("The accessor '" + accessor.getName() +
                                     "' of the module '" +
                                     module->getName() +      // LCOV_EXCL_LINE
                                     "' was not connected!"); // LCOV_EXCL_LINE
      }
    }
  }
}

/*********************************************************************************************************************/

void Application::run() {
  assert(applicationName != "");

  // prepare the modules
  for (auto &module : getSubmoduleListRecursive()) {
    module->prepare();
  }

  // start the necessary threads for the FanOuts etc.
  for (auto &internalModule : internalModuleList) {
    internalModule->activate();
  }

  // read all input variables once, to set the startup value e.g. coming from
  // the config file (without triggering an action inside the application)
  for (auto &module : getSubmoduleListRecursive()) {
    for (auto &variable : module->getAccessorList()) {
      if (variable.getDirection().dir == VariableDirection::consuming) {
        variable.getAppAccessorNoType().readLatest();
      }
    }
  }

  // start the threads for the modules
  for (auto &module : getSubmoduleListRecursive()) {
    std::cout << module->getFullDescription() << std::endl;
    module->run();
  }
  for (auto &deviceModule : deviceModuleList) {
    deviceModule->run();
  }
}

/*********************************************************************************************************************/

void Application::shutdown() {
  // first allow to run the application threads again, if we are in testable
  // mode
  if (testableMode && testableModeTestLock()) {
    testableModeUnlock("shutdown");
  }

  // deactivate the FanOuts first, since they have running threads inside
  // accessing the modules etc. (note: the modules are members of the
  // Application implementation and thus get destroyed after this destructor)
  for (auto &internalModule : internalModuleList) {
    internalModule->deactivate();
  }

  // next deactivate the modules, as they have running threads inside as well
  for (auto &module : getSubmoduleListRecursive()) {
    module->terminate();
  }

  for (auto &deviceModule : deviceModuleList) {
    deviceModule->terminate();
  }
  ApplicationBase::shutdown();
}
/*********************************************************************************************************************/

void Application::generateXML() {
  assert(applicationName != "");

  // define the connections
  defineConnections();

  // also search for unconnected nodes - this is here only executed to print the
  // warnings
  processUnconnectedNodes();

  // finalise connections: decide still-undecided details, in particular for
  // control-system and device varibales, which get created "on the fly".
  finaliseNetworks();

  XMLGeneratorVisitor visitor;
  visitor.dispatch(*this);
  visitor.save(applicationName + ".xml");
}

/*********************************************************************************************************************/

VariableNetwork &Application::connect(VariableNetworkNode a,
                                      VariableNetworkNode b) {
  // if one of the nodes has the value type AnyType, set it to the type of the
  // other if both are AnyType, nothing changes.
  if (a.getValueType() == typeid(AnyType)) {
    a.setValueType(b.getValueType());
  } else if (b.getValueType() == typeid(AnyType)) {
    b.setValueType(a.getValueType());
  }

  // if one of the nodes has not yet a defined number of elements, set it to the
  // number of elements of the other. if both are undefined, nothing changes.
  if (a.getNumberOfElements() == 0) {
    a.setNumberOfElements(b.getNumberOfElements());
  } else if (b.getNumberOfElements() == 0) {
    b.setNumberOfElements(a.getNumberOfElements());
  }
  if (a.getNumberOfElements() != b.getNumberOfElements()) {
    std::stringstream what;
    what << "*** ERROR: Cannot connect array variables with difference number "
            "of elements!"
         << std::endl;
    what << "Node A:" << std::endl;
    a.dump(what);
    what << "Node B:" << std::endl;
    b.dump(what);
    throw ChimeraTK::logic_error(what.str());
  }

  // if both nodes already have an owner, we are either already done (same
  // owners) or we need to try to merge the networks
  if (a.hasOwner() && b.hasOwner()) {
    if (&(a.getOwner()) != &(b.getOwner())) {
      auto &networkToMerge = b.getOwner();
      bool success = a.getOwner().merge(networkToMerge);
      if (!success) {
        std::stringstream what;
        what << "*** ERROR: Trying to connect two nodes which are already part "
                "of different networks, and merging these"
                " networks is not possible (cannot have two non-control-system "
                "or two control-system feeders)!"
             << std::endl;
        what << "Node A:" << std::endl;
        a.dump(what);
        what << "Node B:" << std::endl;
        b.dump(what);
        what << "Owner of node A:" << std::endl;
        a.getOwner().dump("", what);
        what << "Owner of node B:" << std::endl;
        b.getOwner().dump("", what);
        throw ChimeraTK::logic_error(what.str());
      }
      for (auto n = networkList.begin(); n != networkList.end(); ++n) {
        if (&*n == &networkToMerge) {
          networkList.erase(n);
          break;
        }
      }
    }
  }
  // add b to the existing network of a
  else if (a.hasOwner()) {
    a.getOwner().addNode(b);
  }

  // add a to the existing network of b
  else if (b.hasOwner()) {
    b.getOwner().addNode(a);
  }
  // create new network
  else {
    networkList.emplace_back();
    networkList.back().addNode(a);
    networkList.back().addNode(b);
  }
  return a.getOwner();
}

/*********************************************************************************************************************/

template <typename UserType>
boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>
Application::createDeviceVariable(const std::string &deviceAlias,
                                  const std::string &registerName,
                                  VariableDirection direction, UpdateMode mode,
                                  size_t nElements) {
  // open device if needed
  if (deviceMap.count(deviceAlias) == 0) {
    deviceMap[deviceAlias] =
        ChimeraTK::BackendFactory::getInstance().createBackend(deviceAlias);
    if (!deviceMap[deviceAlias]->isOpen())
      deviceMap[deviceAlias]->open();
  }

  // use wait_for_new_data mode if push update mode was requested
  ChimeraTK::AccessModeFlags flags{};
  if (mode == UpdateMode::push && direction.dir == VariableDirection::consuming)
    flags = {AccessMode::wait_for_new_data};

  // obatin the register accessor from the device
  auto accessor = deviceMap[deviceAlias]->getRegisterAccessor<UserType>(
      registerName, nElements, 0, flags);

  // return accessor
  return accessor;
}

/*********************************************************************************************************************/

template <typename UserType>
boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>
Application::createProcessVariable(VariableNetworkNode const &node) {
  // determine the SynchronizationDirection
  SynchronizationDirection dir;
  if (node.getDirection().withReturn) {
    dir = SynchronizationDirection::bidirectional;
  } else if (node.getDirection().dir == VariableDirection::feeding) {
    dir = SynchronizationDirection::controlSystemToDevice;
  } else {
    dir = SynchronizationDirection::deviceToControlSystem;
  }
  AccessModeFlags flags = {};
  if (node.getDirection().dir ==
      VariableDirection::consuming) { // Application-to-controlsystem must be
                                      // push-type
    flags = {AccessMode::wait_for_new_data};
  } else {
    for (auto &consumer : node.getOwner().getConsumingNodes()) {
      if (consumer.getMode() == UpdateMode::push)
        flags = {AccessMode::wait_for_new_data};
    }
  }

  // create the ProcessArray for the proper UserType
  auto pvar = _processVariableManager->createProcessArray<UserType>(
      dir, node.getPublicName(), node.getNumberOfElements(),
      node.getOwner().getUnit(), node.getOwner().getDescription(), {}, false, 3,
      flags);
  assert(pvar->getName() != "");

  // create variable ID
  auto varId = getNextVariableId();
  pvIdMap[pvar->getUniqueId()] = varId;

  // Decorate the process variable if testable mode is enabled and this is the
  // receiving end of the variable. Also don't decorate, if the mode is polling.
  // Instead flag the variable to be polling, so the TestFacility is aware of
  // this.
  if (testableMode && node.getDirection().dir == VariableDirection::feeding) {
    // The transfer mode of this process variable is considered to be polling,
    // if only one consumer exists and this consumer is polling. Reason:
    // mulitple consumers will result in the use of a FanOut, so the
    // communication up to the FanOut will be push-type, even if all consumers
    // are poll-type.
    /// @todo Check if this is true!
    auto mode = UpdateMode::push;
    if (node.getOwner().countConsumingNodes() == 1) {
      if (node.getOwner().getConsumingNodes().front().getMode() ==
          UpdateMode::poll)
        mode = UpdateMode::poll;
    }

    if (mode != UpdateMode::poll) {
      auto pvarDec =
          boost::make_shared<TestableModeAccessorDecorator<UserType>>(
              pvar, true, false, varId, varId);
      testableMode_names[varId] = "ControlSystem:" + node.getPublicName();
      return pvarDec;
    } else {
      testableMode_isPollMode[varId] = true;
    }
  }

  // return the process variable
  return pvar;
}

/*********************************************************************************************************************/

template <typename UserType>
std::pair<boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>,
          boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>>
Application::createApplicationVariable(VariableNetworkNode const &node,
                                       VariableNetworkNode const &consumer) {
  // obtain the meta data
  size_t nElements = node.getNumberOfElements();
  std::string name = node.getName();
  assert(name != "");
  AccessModeFlags flags = {};
  if (consumer.getType() != NodeType::invalid) {
    if (consumer.getMode() == UpdateMode::push)
      flags = {AccessMode::wait_for_new_data};
  } else {
    if (node.getMode() == UpdateMode::push)
      flags = {AccessMode::wait_for_new_data};
  }

  // create the ProcessArray for the proper UserType
  std::pair<boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>,
            boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>>>
      pvarPair;
  if (consumer.getType() != NodeType::invalid)
    assert(node.getDirection().withReturn ==
           consumer.getDirection().withReturn);
  if (!node.getDirection().withReturn) {
    pvarPair = createSynchronizedProcessArray<UserType>(
        nElements, name, node.getUnit(), node.getDescription(), {}, 3, false,
        {}, flags);
  } else {
    pvarPair = createBidirectionalSynchronizedProcessArray<UserType>(
        nElements, name, node.getUnit(), node.getDescription(), {}, 3, {}, {},
        flags);
  }
  assert(pvarPair.first->getName() != "");
  assert(pvarPair.second->getName() != "");

  // create variable IDs
  size_t varId = getNextVariableId();
  size_t varIdReturn;
  if (node.getDirection().withReturn)
    varIdReturn = getNextVariableId();

  // decorate the process variable if testable mode is enabled and mode is
  // push-type
  if (testableMode && node.getMode() == UpdateMode::push) {
    if (!node.getDirection().withReturn) {
      pvarPair.first =
          boost::make_shared<TestableModeAccessorDecorator<UserType>>(
              pvarPair.first, false, true, varId, varId);
      pvarPair.second =
          boost::make_shared<TestableModeAccessorDecorator<UserType>>(
              pvarPair.second, true, false, varId, varId);
    } else {
      pvarPair.first =
          boost::make_shared<TestableModeAccessorDecorator<UserType>>(
              pvarPair.first, true, true, varIdReturn, varId);
      pvarPair.second =
          boost::make_shared<TestableModeAccessorDecorator<UserType>>(
              pvarPair.second, true, true, varId, varIdReturn);
    }

    // put the decorators into the list
    testableMode_names[varId] = "Internal:" + node.getQualifiedName();
    if (consumer.getType() != NodeType::invalid) {
      testableMode_names[varId] += "->" + consumer.getQualifiedName();
    }
    if (node.getDirection().withReturn)
      testableMode_names[varIdReturn] = testableMode_names[varId] + " (return)";
  }

  // if debug mode was requested for either node, decorate both accessors
  if (debugMode_variableList.count(node.getUniqueId()) ||
      (consumer.getType() != NodeType::invalid &&
       debugMode_variableList.count(consumer.getUniqueId()))) {
    if (consumer.getType() != NodeType::invalid) {
      assert(node.getDirection().dir == VariableDirection::feeding);
      assert(consumer.getDirection().dir == VariableDirection::consuming);
      pvarPair.first =
          boost::make_shared<DebugPrintAccessorDecorator<UserType>>(
              pvarPair.first, node.getQualifiedName());
      pvarPair.second =
          boost::make_shared<DebugPrintAccessorDecorator<UserType>>(
              pvarPair.second, consumer.getQualifiedName());
    } else {
      pvarPair.first =
          boost::make_shared<DebugPrintAccessorDecorator<UserType>>(
              pvarPair.first, node.getQualifiedName());
      pvarPair.second =
          boost::make_shared<DebugPrintAccessorDecorator<UserType>>(
              pvarPair.second, node.getQualifiedName());
    }
  }

  // return the pair
  return pvarPair;
}

/*********************************************************************************************************************/

void Application::makeConnections() {
  for (auto &devModule : deviceModuleList) {
    devModule->defineConnections();
  }
  // finalise connections: decide still-undecided details, in particular for
  // control-system and device varibales, which get created "on the fly".
  finaliseNetworks();

  // apply optimisations
  // note: checks may not be run before since sometimes networks may only be
  // valid after optimisations
  optimiseConnections();

  // run checks
  checkConnections();

  // make the connections for all networks
  for (auto &network : networkList) {
    makeConnectionsForNetwork(network);
  }

  // set all initial version numbers in the modules to the same value
  VersionNumber startVersion;
  for (auto &module : getSubmoduleListRecursive()) {
    if (module->getModuleType() != ModuleType::ApplicationModule)
      continue;
    module->setCurrentVersionNumber(startVersion);
  }
}

/*********************************************************************************************************************/

void Application::finaliseNetworks() {
  // check for control system variables which should be made bidirectional
  for (auto &network : networkList) {
    size_t nBidir = network.getFeedingNode().getDirection().withReturn ? 1 : 0;
    for (auto &consumer : network.getConsumingNodes()) {
      if (consumer.getDirection().withReturn)
        ++nBidir;
    }
    if (nBidir != 1)
      continue; // only if there is exactly one node with return channel we need
                // to guess its peer
    if (network.getFeedingNode().getType() != NodeType::ControlSystem) {
      // only a feeding control system variable can be made bidirectional
      continue;
    }
    network.getFeedingNode().setDirection({VariableDirection::feeding, true});
  }
}

/*********************************************************************************************************************/

void Application::optimiseConnections() {
  // list of iterators of networks to be removed from the networkList after the
  // merge operation
  std::list<VariableNetwork *> deleteNetworks;

  // search for networks with the same feeder
  for (auto it1 = networkList.begin(); it1 != networkList.end(); ++it1) {
    for (auto it2 = it1; it2 != networkList.end(); ++it2) {
      if (it1 == it2)
        continue;

      auto feeder1 = it1->getFeedingNode();
      auto feeder2 = it2->getFeedingNode();

      // this optimisation is only necessary for device-type nodes, since
      // application and control-system nodes will automatically create merged
      // networks when having the same feeder
      /// @todo check if this assumtion is true! control-system nodes can be
      /// created with different types, too!
      if (feeder1.getType() != NodeType::Device ||
          feeder2.getType() != NodeType::Device)
        continue;

      // check if referrring to same register
      if (feeder1.getDeviceAlias() != feeder2.getDeviceAlias())
        continue;
      if (feeder1.getRegisterName() != feeder2.getRegisterName())
        continue;

      // check if directions are the same
      if (feeder1.getDirection() != feeder2.getDirection())
        continue;

      // check if value types and number of elements are compatible
      if (feeder1.getValueType() != feeder2.getValueType())
        continue;
      if (feeder1.getNumberOfElements() != feeder2.getNumberOfElements())
        continue;

      // check if transfer mode is the same
      if (feeder1.getMode() != feeder2.getMode())
        continue;

      // check if triggers are compatible, if present
      if (feeder1.hasExternalTrigger() != feeder2.hasExternalTrigger())
        continue;
      if (feeder1.hasExternalTrigger()) {
        if (feeder1.getExternalTrigger() != feeder2.getExternalTrigger())
          continue;
      }

      // everything should be compatible at this point: merge the networks. We
      // will merge the network of the outer loop into the network of the inner
      // loop, since the network of the outer loop will not be found a second
      // time in the inner loop.
      for (auto consumer : it1->getConsumingNodes()) {
        consumer.clearOwner();
        it2->addNode(consumer);
      }

      // if trigger present, remove corresponding trigger receiver node from the
      // trigger network
      if (feeder1.hasExternalTrigger()) {
        for (auto &itTrig : networkList) {
          if (itTrig.getFeedingNode() != feeder1.getExternalTrigger())
            continue;
          itTrig.removeNodeToTrigger(it1->getFeedingNode());
        }
      }

      // schedule the outer loop network for deletion and stop processing it
      deleteNetworks.push_back(&(*it1));
      break;
    }
  }

  // remove networks from the network list
  for (auto net : deleteNetworks) {
    networkList.remove(*net);
  }
}

/*********************************************************************************************************************/

void Application::dumpConnections() { // LCOV_EXCL_LINE
  std::cout
      << "==== List of all variable connections of the current Application ===="
      << std::endl;                   // LCOV_EXCL_LINE
  for (auto &network : networkList) { // LCOV_EXCL_LINE
    network.dump();                   // LCOV_EXCL_LINE
  }                                   // LCOV_EXCL_LINE
  std::cout
      << "====================================================================="
      << std::endl; // LCOV_EXCL_LINE
} // LCOV_EXCL_LINE

void Application::dumpConnectionGraph(const std::string &fileName) {
  std::fstream file{fileName, std::ios_base::out};

  VariableNetworkGraphDumpingVisitor visitor{file};
  visitor.dispatch(*this);
}

/*********************************************************************************************************************/

Application::TypedMakeConnectionCaller::TypedMakeConnectionCaller(
    Application &owner, VariableNetwork &network)
    : _owner(owner), _network(network) {}

/*********************************************************************************************************************/

template <typename PAIR>
void Application::TypedMakeConnectionCaller::operator()(PAIR &) const {
  if (typeid(typename PAIR::first_type) != _network.getValueType())
    return;
  _owner.typedMakeConnection<typename PAIR::first_type>(_network);
  done = true;
}

/*********************************************************************************************************************/

void Application::makeConnectionsForNetwork(VariableNetwork &network) {
  // if the network has been created already, do nothing
  if (network.isCreated())
    return;

  // if the trigger type is external, create the trigger first
  if (network.getFeedingNode().hasExternalTrigger()) {
    VariableNetwork &dependency =
        network.getFeedingNode().getExternalTrigger().getOwner();
    if (!dependency.isCreated())
      makeConnectionsForNetwork(dependency);
  }

  // defer actual network creation to templated function
  auto callable = TypedMakeConnectionCaller(*this, network);
  boost::fusion::for_each(ChimeraTK::userTypeMap(), std::ref(callable));
  assert(callable.done);

  // mark the network as created
  network.markCreated();
}

/*********************************************************************************************************************/

template <typename UserType>
void Application::typedMakeConnection(VariableNetwork &network) {
  bool connectionMade = false; // to check the logic...

  size_t nNodes = network.countConsumingNodes() + 1;
  auto feeder = network.getFeedingNode();
  auto consumers = network.getConsumingNodes();
  bool useExternalTrigger =
      network.getTriggerType() == VariableNetwork::TriggerType::external;
  bool useFeederTrigger =
      network.getTriggerType() == VariableNetwork::TriggerType::feeder;
  bool constantFeeder = feeder.getType() == NodeType::Constant;

  // 1st case: the feeder requires a fixed implementation
  if (feeder.hasImplementation() && !constantFeeder) {
    // Create feeding implementation. Note: though the implementation is derived
    // from the feeder, it will be used as the implementation of the (or one of
    // the) consumer. Logically, implementations are always pairs of
    // implementations (sender and receiver), but in this case the feeder
    // already has a fixed implementation pair. So our feedingImpl will contain
    // the consumer-end of the implementation pair. This is the reason why the
    // functions createProcessScalar() and createDeviceAccessor() get the
    // VariableDirection::consuming.
    boost::shared_ptr<ChimeraTK::NDRegisterAccessor<UserType>> feedingImpl;
    if (feeder.getType() == NodeType::Device) {
      feedingImpl = createDeviceVariable<UserType>(
          feeder.getDeviceAlias(), feeder.getRegisterName(),
          {VariableDirection::consuming, false}, feeder.getMode(),
          feeder.getNumberOfElements());
    } else if (feeder.getType() == NodeType::ControlSystem) {
      feedingImpl = createProcessVariable<UserType>(feeder);
    } else {
      throw ChimeraTK::logic_error(
          "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
    }

    // if we just have two nodes, directly connect them
    if (nNodes == 2 && !useExternalTrigger) {
      auto consumer = consumers.front();
      if (consumer.getType() == NodeType::Application) {
        consumer.setAppAccessorImplementation(feedingImpl);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::Device) {
        auto consumingImpl = createDeviceVariable<UserType>(
            consumer.getDeviceAlias(), consumer.getRegisterName(),
            {VariableDirection::feeding, false}, consumer.getMode(),
            consumer.getNumberOfElements());
        // connect the Device with e.g. a ControlSystem node via a
        // ThreadedFanOut
        auto fanOut = boost::make_shared<ThreadedFanOut<UserType>>(feedingImpl);
        fanOut->addSlave(consumingImpl, consumer);
        internalModuleList.push_back(fanOut);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::ControlSystem) {
        auto consumingImpl = createProcessVariable<UserType>(consumer);
        // connect the ControlSystem with e.g. a Device node via an
        // ThreadedFanOut
        auto fanOut = boost::make_shared<ThreadedFanOut<UserType>>(feedingImpl);
        fanOut->addSlave(consumingImpl, consumer);
        internalModuleList.push_back(fanOut);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::TriggerReceiver) {
        consumer.getNodeToTrigger().getOwner().setExternalTriggerImpl(
            feedingImpl);
        connectionMade = true;
      } else {
        throw ChimeraTK::logic_error(
            "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
      }
    } else { /* !(nNodes == 2 && !useExternalTrigger) */

      // create the right FanOut type
      boost::shared_ptr<FanOut<UserType>> fanOut;
      boost::shared_ptr<ConsumingFanOut<UserType>> consumingFanOut;
      if (useExternalTrigger) {
        // if external trigger is enabled, use externally triggered threaded
        // FanOut
        auto triggerNode = feeder.getExternalTrigger();
        auto triggerFanOut = triggerMap[triggerNode.getUniqueId()];
        if (!triggerFanOut) {
          triggerFanOut = boost::make_shared<TriggerFanOut>(
              network.getExternalTriggerImpl());
          triggerMap[triggerNode.getUniqueId()] = triggerFanOut;
          internalModuleList.push_back(triggerFanOut);
        }
        fanOut = triggerFanOut->addNetwork(feedingImpl);
      } else if (useFeederTrigger) {
        // if the trigger is provided by the pushing feeder, use the treaded
        // version of the FanOut to distribute new values immediately to all
        // consumers. Depending on whether we have a return channel or not, pick
        // the right implementation of the FanOut
        boost::shared_ptr<ThreadedFanOut<UserType>> threadedFanOut;
        if (!feeder.getDirection().withReturn) {
          threadedFanOut =
              boost::make_shared<ThreadedFanOut<UserType>>(feedingImpl);
        } else {
          threadedFanOut =
              boost::make_shared<ThreadedFanOutWithReturn<UserType>>(
                  feedingImpl);
        }
        internalModuleList.push_back(threadedFanOut);
        fanOut = threadedFanOut;
      } else {
        assert(network.hasApplicationConsumer()); // checkConnections should
                                                  // catch this
        consumingFanOut =
            boost::make_shared<ConsumingFanOut<UserType>>(feedingImpl);
        fanOut = consumingFanOut;
      }

      // In case we have one or more trigger receivers among our consumers, we
      // produce exactly one application variable for it. We never need more,
      // since the distribution is done with a TriggerFanOut.
      bool usedTriggerReceiver{
          false}; // flag if we already have a trigger receiver
      auto triggerConnection = createApplicationVariable<UserType>(
          feeder); // will get destroyed if not used

      // add all consumers to the FanOut
      for (auto &consumer : consumers) {
        if (consumer.getType() == NodeType::Application) {
          if (consumingFanOut && consumer.getMode() == UpdateMode::poll) {
            consumer.setAppAccessorImplementation<UserType>(consumingFanOut);
            consumingFanOut.reset();
          } else {
            auto impls = createApplicationVariable<UserType>(consumer);
            fanOut->addSlave(impls.first, consumer);
            consumer.setAppAccessorImplementation<UserType>(impls.second);
          }
        } else if (consumer.getType() == NodeType::ControlSystem) {
          auto impl = createProcessVariable<UserType>(consumer);
          fanOut->addSlave(impl, consumer);
        } else if (consumer.getType() == NodeType::Device) {
          auto impl = createDeviceVariable<UserType>(
              consumer.getDeviceAlias(), consumer.getRegisterName(),
              {VariableDirection::feeding, false}, consumer.getMode(),
              consumer.getNumberOfElements());
          fanOut->addSlave(impl, consumer);
        } else if (consumer.getType() == NodeType::TriggerReceiver) {
          if (!usedTriggerReceiver)
            fanOut->addSlave(triggerConnection.first, consumer);
          usedTriggerReceiver = true;
          consumer.getNodeToTrigger().getOwner().setExternalTriggerImpl(
              triggerConnection.second);
        } else {
          throw ChimeraTK::logic_error(
              "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
        }
      }
      connectionMade = true;
    }
  }
  // 2nd case: the feeder does not require a fixed implementation
  else if (!constantFeeder) { /* !feeder.hasImplementation() */
    // we should be left with an application feeder node
    if (feeder.getType() != NodeType::Application) {
      throw ChimeraTK::logic_error(
          "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
    }
    assert(!useExternalTrigger);
    // if we just have two nodes, directly connect them
    if (nNodes == 2) {
      auto consumer = consumers.front();
      if (consumer.getType() == NodeType::Application) {
        auto impls = createApplicationVariable<UserType>(feeder, consumer);
        feeder.setAppAccessorImplementation<UserType>(impls.first);
        consumer.setAppAccessorImplementation<UserType>(impls.second);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::ControlSystem) {
        auto impl = createProcessVariable<UserType>(consumer);
        feeder.setAppAccessorImplementation<UserType>(impl);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::Device) {
        auto impl = createDeviceVariable<UserType>(
            consumer.getDeviceAlias(), consumer.getRegisterName(),
            {VariableDirection::feeding, false}, consumer.getMode(),
            consumer.getNumberOfElements());
        feeder.setAppAccessorImplementation<UserType>(impl);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::TriggerReceiver) {
        auto impls = createApplicationVariable<UserType>(feeder, consumer);
        feeder.setAppAccessorImplementation<UserType>(impls.first);
        consumer.getNodeToTrigger().getOwner().setExternalTriggerImpl(
            impls.second);
        connectionMade = true;
      } else if (consumer.getType() == NodeType::Constant) {
        auto impl = consumer.getConstAccessor<UserType>();
        feeder.setAppAccessorImplementation<UserType>(impl);
        connectionMade = true;
      } else {
        throw ChimeraTK::logic_error(
            "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
      }
    } else {
      // create FanOut and use it as the feeder implementation
      auto fanOut = boost::make_shared<FeedingFanOut<UserType>>(
          feeder.getName(), feeder.getUnit(), feeder.getDescription(),
          feeder.getNumberOfElements(), feeder.getDirection().withReturn);
      feeder.setAppAccessorImplementation<UserType>(fanOut);

      // In case we have one or more trigger receivers among our consumers, we
      // produce exactly one application variable for it. We never need more,
      // since the distribution is done with a TriggerFanOut.
      bool usedTriggerReceiver{
          false}; // flag if we already have a trigger receiver
      auto triggerConnection = createApplicationVariable<UserType>(
          feeder); // will get destroyed if not used

      for (auto &consumer : consumers) {
        if (consumer.getType() == NodeType::Application) {
          auto impls = createApplicationVariable<UserType>(consumer);
          fanOut->addSlave(impls.first, consumer);
          consumer.setAppAccessorImplementation<UserType>(impls.second);
        } else if (consumer.getType() == NodeType::ControlSystem) {
          auto impl = createProcessVariable<UserType>(consumer);
          fanOut->addSlave(impl, consumer);
        } else if (consumer.getType() == NodeType::Device) {
          auto impl = createDeviceVariable<UserType>(
              consumer.getDeviceAlias(), consumer.getRegisterName(),
              {VariableDirection::feeding, false}, consumer.getMode(),
              consumer.getNumberOfElements());
          fanOut->addSlave(impl, consumer);
        } else if (consumer.getType() == NodeType::TriggerReceiver) {
          if (!usedTriggerReceiver)
            fanOut->addSlave(triggerConnection.first, consumer);
          usedTriggerReceiver = true;
          consumer.getNodeToTrigger().getOwner().setExternalTriggerImpl(
              triggerConnection.second);
        } else {
          throw ChimeraTK::logic_error(
              "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
        }
      }
      connectionMade = true;
    }
  } else { /* constantFeeder */
    assert(feeder.getType() == NodeType::Constant);
    auto feedingImpl = feeder.getConstAccessor<UserType>();
    assert(feedingImpl != nullptr);

    for (auto &consumer : consumers) {
      if (consumer.getType() == NodeType::Application) {
        if (testableMode) {
          auto varId = getNextVariableId();
          auto pvarDec =
              boost::make_shared<TestableModeAccessorDecorator<UserType>>(
                  feedingImpl, true, false, varId, varId);
          testableMode_names[varId] = "Constant";
          consumer.setAppAccessorImplementation<UserType>(pvarDec);
        } else {
          consumer.setAppAccessorImplementation<UserType>(feedingImpl);
        }
      } else if (consumer.getType() == NodeType::ControlSystem) {
        auto impl = createProcessVariable<UserType>(consumer);
        impl->accessChannel(0) = feedingImpl->accessChannel(0);
        impl->write();
      } else if (consumer.getType() == NodeType::Device) {
        auto impl = createDeviceVariable<UserType>(
            consumer.getDeviceAlias(), consumer.getRegisterName(),
            {VariableDirection::feeding, false}, consumer.getMode(),
            consumer.getNumberOfElements());
        impl->accessChannel(0) = feedingImpl->accessChannel(0);
        impl->write();
      } else if (consumer.getType() == NodeType::TriggerReceiver) {
        throw ChimeraTK::logic_error(
            "Using constants as triggers is not supported!");
      } else {
        throw ChimeraTK::logic_error(
            "Unexpected node type!"); // LCOV_EXCL_LINE (assert-like)
      }
    }
    connectionMade = true;
  }

  if (!connectionMade) {          // LCOV_EXCL_LINE (assert-like)
    throw ChimeraTK::logic_error( // LCOV_EXCL_LINE (assert-like)
        "The variable network cannot be handled. Implementation missing!"); // LCOV_EXCL_LINE (assert-like)
  } // LCOV_EXCL_LINE (assert-like)
}

/*********************************************************************************************************************/

VariableNetwork &Application::createNetwork() {
  networkList.emplace_back();
  return networkList.back();
}