StateMachine.cpp

Go to the documentation of this file.

#include "Engine.h"
#include "StateMachine.h"
#include "Token.h"
#include "SystemState.h"
#include "Event.h"
#include "execution/utility/src/erase.h"
#include "model/bpmnos/src/extensionElements/ExtensionElements.h"
#include "model/bpmnos/src/extensionElements/Timer.h"
#include "model/utility/src/CollectionRegistry.h"
#include "bpmn++.h"
#include <cassert>
#include <ranges>
 
using namespace BPMNOS::Execution;
 
StateMachine::StateMachine(const SystemState* systemState, const BPMN::Process* process, Values dataAttributes)
  : systemState(systemState)
  , process(process)
  , scope(process)
  , root(this)
  , instance( dataAttributes.size() ? dataAttributes[BPMNOS::Model::ExtensionElements::Index::Instance] : -1 )
  , parentToken(nullptr)
  , ownedData(dataAttributes)
  , data(SharedValues(ownedData))
{
  assert( instance.has_value() && instance.value() >= 0 );
  data[BPMNOS::Model::ExtensionElements::Index::Instance] = std::ref(instance);
}
 
StateMachine::StateMachine(const SystemState* systemState, const BPMN::Scope* scope, Token* parentToken, Values dataAttributes, std::optional<BPMNOS::number> instance )
  : systemState(systemState)
  , process(parentToken->owner->process)
  , scope(scope)
  , root(parentToken->owner->root)
  , instance(instance.value_or( (*parentToken->data)[BPMNOS::Model::ExtensionElements::Index::Instance].get().value() ) )
  , parentToken(parentToken)
  , ownedData(dataAttributes)
  , data(SharedValues(parentToken->owner->data,ownedData))
{
  
  data[BPMNOS::Model::ExtensionElements::Index::Instance] = std::ref(this->instance);
/*
std::cerr << "child StateMachine(" << scope->id << "/" << this << " @ " << parentToken << ")" << " owned by: " << parentToken->owner << std::endl;
//std::cerr << data.size() << "[" <<BPMNOS::Model::ExtensionElements::Index::Instance <<"] = " << data[BPMNOS::Model::ExtensionElements::Index::Instance].value_or(-1) <<  "/" << ( data.size() ? (int)data[BPMNOS::Model::ExtensionElements::Index::Instance].get().value_or(-1) : -1 ) << "/" << instance << "/" << this->instance <<std::endl;
std::cerr << "data: ";
for ( auto& attribute : data ) {
std::cerr << (int)attribute.get().value() << ", ";
}
std::cerr << std::endl;
*/
  assert( this->instance.has_value() && this->instance.value() >= 0 );
}
 
StateMachine::StateMachine(const StateMachine* other)
  : systemState(other->systemState)
  , process(other->process)
  , scope(other->scope)
  , root(other->root)
  , instance( other->instance )
  , parentToken(other->parentToken)
  , ownedData(other->ownedData)
  , data(SharedValues(parentToken->owner->data,ownedData))
{
//std::cerr << "oStateMachine(" << scope->id << "/" << this << " @ " << parentToken << ")"  << " owned by :" << parentToken->owner << std::endl;
  data[BPMNOS::Model::ExtensionElements::Index::Instance] = std::ref(instance);
}
 
StateMachine::~StateMachine() {
//std::cerr << "~StateMachine()" << std::endl;
  const_cast<SystemState*>(systemState)->tokensAwaitingGatewayActivation.erase(this);
  const_cast<SystemState*>(systemState)->tokenAwaitingCompensationEventSubProcess.erase(this);
  if ( !systemState->inbox.empty() && scope ) {
    unregisterRecipient();
  }
}
 
BPMNOS::Values StateMachine::getData(const BPMN::Scope* scope) {
  throw std::runtime_error("StateMachine: data is not yet known for scope '" + scope->id + "'");
}
 
void StateMachine::initiateBoundaryEvents(Token* token) {
//std::cerr << "initiateBoundaryEvents: " << token->node->id << std::endl;
  auto activity = token->node->as<BPMN::Activity>();
  assert( activity);
 
  if ( activity->loopCharacteristics.has_value() &&
    activity->loopCharacteristics.value() != BPMN::Activity::LoopCharacteristics::Standard
  ) {
    // determine main token waiting for all instances
    auto mainToken = const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.at(token);
 
    if ( const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent[mainToken].empty() ) {
      // create boundary event tokens for the main token
      token = mainToken; 
    }
    else {
      // tokens at boundary events have already been created 
      return;
    }
  }
 
  for ( auto node : activity->boundaryEvents ) {
    if ( !node->represents<BPMN::CompensateBoundaryEvent>() ) {
      initiateBoundaryEvent(token,node);
    }
  }
}
 
void StateMachine::initiateBoundaryEvent(Token* token, const BPMN::FlowNode* node) {
  tokens.push_back( std::make_shared<Token>(this,node,token->status) );
  auto createdToken = tokens.back().get();
  const_cast<SystemState*>(systemState)->tokenAssociatedToBoundaryEventToken[createdToken] = token;
  const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent[token].push_back(createdToken);
  createdToken->advanceToEntered();
}
 
void StateMachine::initiateEventSubprocesses(Token* token) {
//std::cerr << "initiate " << scope->eventSubProcesses.size() << " eventSubprocesses for token at " << (token->node ? token->node->id : process->id ) << "/" << parentToken << "/" << token << " owned by " << token->owner << std::endl;
  for ( auto& eventSubProcess : scope->eventSubProcesses ) {
    auto data = systemState->getDataAttributes(root,eventSubProcess);
    if ( !data.has_value() ) {
      throw std::runtime_error("StateMachine: required data at '" + eventSubProcess->id +"' not yet available" );
    }
    pendingEventSubProcesses.push_back(std::make_shared<StateMachine>( systemState, eventSubProcess, parentToken, std::move(data.value()) ) );
    auto pendingEventSubProcess = pendingEventSubProcesses.back().get();
//std::cerr << "Pending event subprocess has parent: " << pendingEventSubProcess->parentToken->jsonify().dump() << std::endl;
 
    pendingEventSubProcess->run(token->status);
  }
}
 
void StateMachine::createMultiInstanceActivityTokens(Token* token) {
  auto extensionElements = token->node->extensionElements->represents<const BPMNOS::Model::ExtensionElements>();
  assert( extensionElements != nullptr );
 
  std::vector< std::map< const Model::Attribute*, std::optional<BPMNOS::number> > > valueMaps;
 
  if ( extensionElements->loopCardinality.has_value() ) {
    auto getLoopCardinality = [token,extensionElements]() -> std::optional<BPMNOS::number> {
      if (!extensionElements->loopCardinality.value()->expression) {
        return std::nullopt;
      }
      return extensionElements->loopCardinality.value()->expression->execute(token->status, *token->data, token->globals);
    };
    // use provided cardinality to determine number of tokens 
    if ( auto loopCardinality = getLoopCardinality();
      loopCardinality.has_value()
    ) {
      valueMaps.resize( (size_t)loopCardinality.value() );
    }
    else {
      throw std::runtime_error("StateMachine: cannot determine cardinality for multi-instance activity '" + token->node->id +"'" );
    }
  }
  
  if ( extensionElements->messageDefinitions.size() ) {
    if ( valueMaps.empty() ) {
      valueMaps.resize(extensionElements->messageDefinitions.size());
    }
    else if ( valueMaps.size() != extensionElements->messageDefinitions.size() ) {
      throw std::runtime_error("StateMachine: cardinality and number of messages inconsistent for multi-instance activity '" + token->node->id +"'" );
    }
  }
 
  if ( valueMaps.empty() ) {
    throw std::runtime_error("StateMachine: no instances created for multi-instance activity '" + token->node->id +"'" );
  }
 
  if ( extensionElements->loopIndex.has_value() && extensionElements->loopIndex.value()->expression ) {
    // set value of loop index attribute for each instance
    if ( auto attribute = extensionElements->loopIndex.value()->expression->isAttribute() ) {
      for ( size_t i = 0; i < valueMaps.size(); i++ ) {
        valueMaps[i][attribute] = i + 1;
      }
    }
    else {
      throw std::runtime_error("StateMachine: no attribute provided for loop index parameter of multi-instance activity '" + token->node->id +"'" );
    }
  }
 
  auto activity = token->node->represents<BPMN::Activity>();
  assert( activity );
  assert( activity->loopCharacteristics.has_value() );
 
  // create token copies
  assert ( systemState->tokensAtActivityInstance.find(token) == systemState->tokensAtActivityInstance.end() );
  assert ( systemState->exitStatusAtActivityInstance.find(token) == systemState->exitStatusAtActivityInstance.end() );
 
  Token* tokenCopy = nullptr;
  size_t counter = 0;
  for ( auto valueMap : valueMaps ) {
    counter++;
    // disambiguate instance id
    auto instanceId = BPMNOS::to_string(this->data[BPMNOS::Model::ExtensionElements::Index::Instance].get().value(),STRING) + BPMNOS::Model::Scenario::delimiters[0] + token->node->id + BPMNOS::Model::Scenario::delimiters[1] +  std::to_string(counter);
 
    tokens.push_back( std::make_shared<Token>( token ) );
    if ( auto scope = token->node->represents<BPMN::Scope>() ) {
      // create state machine for each multi-instance subprocess
      auto data = systemState->getDataAttributes(root,token->node);     
      if ( !data.has_value() ) {
        throw std::runtime_error("StateMachine: required data at '" + token->node->id +"' not yet available" );
      }
 
      // create child state machine with disambiguated instance identifier
      createChild( tokens.back().get(), scope, std::move(data.value()), BPMNOS::to_number(instanceId,BPMNOS::ValueType::STRING) );
      // ensure that data is set appropriately
      tokens.back()->data = &tokens.back()->owned->data;
//std::cerr << "MI:" << instanceId << "/" << tokens.back()->jsonify() << std::endl;      
    }
    else {
      // create child fake state machine with disambiguated instance identifier
      createChild( tokens.back().get(), nullptr, {}, BPMNOS::to_number(instanceId,BPMNOS::ValueType::STRING) );
      // ensure that data is set appropriately
      tokens.back()->data = &tokens.back()->owned->data;
//std::cerr << "Fake:" << tokens.back()->jsonify() << std::endl;      
    }       
    
    // update status of token copy
    for ( auto [attribute,value] : valueMap ) {
      tokens.back().get()->status[attribute->index] = value;
    }
 
    if ( activity->loopCharacteristics.value() == BPMN::Activity::LoopCharacteristics::MultiInstanceSequential ) {
      if ( !tokenCopy ) {
        // for sequential multi-instance activities only the first token awaits entry event
        tokens.back().get()->update(Token::State::READY);
//std::cerr << "Token awaiting entry:" << tokens.back()->jsonify() << std::endl;
        tokens.back().get()->awaitEntryEvent();
      }
      else {
        // newly created tokens have to wait for previous token copy
        const_cast<SystemState*>(systemState)->tokenAwaitingMultiInstanceExit[tokenCopy] = tokens.back().get();
      }
    }
    else if ( activity->loopCharacteristics.value() == BPMN::Activity::LoopCharacteristics::MultiInstanceParallel ) {
      // for parallel multi-instance activities all new tokens await entry event
      tokens.back().get()->update(Token::State::READY);
//std::cerr << "Token awaiting entry:" << tokens.back()->jsonify() << std::endl;
      tokens.back().get()->awaitEntryEvent();
    }
 
    tokenCopy = tokens.back().get();
    const_cast<SystemState*>(systemState)->tokensAtActivityInstance[token].push_back(tokenCopy);
    const_cast<SystemState*>(systemState)->exitStatusAtActivityInstance[token] = {};
    const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity[tokenCopy] = token;
  }
 
  assert( tokenCopy );
 
  // change state of original token
  token->update(Token::State::WAITING);
}
 
void StateMachine::deleteMultiInstanceActivityToken(Token* token) {
  auto engine = const_cast<Engine*>(systemState->engine);
  auto mainToken = const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.at(token);
 
  auto activity = token->node->represents<BPMN::Activity>();
  assert( activity );
 
  if ( activity->loopCharacteristics.value() == BPMN::Activity::LoopCharacteristics::MultiInstanceSequential ) {
    // advance next token for sequential multi-instance activity
    auto& tokenAwaitingMultiInstanceExit = const_cast<SystemState*>(systemState)->tokenAwaitingMultiInstanceExit;
    auto it = tokenAwaitingMultiInstanceExit.find(token);
  
    if ( it != tokenAwaitingMultiInstanceExit.end() ) {
      auto waitingToken = it->second;
      waitingToken->awaitEntryEvent();
      tokenAwaitingMultiInstanceExit.erase(it);
    }
  }
 
  // record exit status
  const_cast<SystemState*>(systemState)->exitStatusAtActivityInstance[mainToken].push_back(token->status);
  // remove token
  const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.erase(token);
  erase_ptr<Token>(const_cast<SystemState*>(systemState)->tokensAtActivityInstance[mainToken],token);
  erase_ptr<Token>(tokens,token);
 
  // advance main token when last multi-instance token exited
  auto& tokensAtActivityInstance = const_cast<SystemState*>(systemState)->tokensAtActivityInstance;
  if ( auto it1 = tokensAtActivityInstance.find(mainToken);
    it1 != tokensAtActivityInstance.end()
  ) {
    if ( it1->second.empty() ) {
      // last multi-instance token exited
      tokensAtActivityInstance.erase(it1);
 
      if ( !activity->boundaryEvents.empty() ) {
        // remove tokens at boundary events
        deleteTokensAwaitingBoundaryEvent( mainToken );
      }
 
      auto& exitStatusAtActivityInstance = const_cast<SystemState*>(systemState)->exitStatusAtActivityInstance;
      if ( auto it2 = exitStatusAtActivityInstance.find(mainToken);
         it2 != exitStatusAtActivityInstance.end()
      ) {
        // merge status 
        mainToken->status = BPMNOS::mergeValues(it2->second);
        exitStatusAtActivityInstance.erase(it2);
      }
 
      // advance main token
      if ( mainToken->node->outgoing.empty() ) {
        engine->commands.emplace_back(std::bind(&Token::advanceToDone,mainToken), mainToken);
      }
      else {
        engine->commands.emplace_back(std::bind(&Token::advanceToDeparting,mainToken), mainToken);
      }
    }
  }
  else {
    assert(!"cannot find tokens created for multi instance activity");
  }
}
// TODO: handle failure events
// TODO: handle single-instance compensations
// TODO: handle parallel compensations
// TODO: set value from csv input
// TODO: type vector (must be immutable)
// TODO: check conditions for immutable  
 
void StateMachine::deleteAdHocSubProcessToken(Token* token) {
  if ( tokens.size() > 1 ) {
    erase_ptr<Token>(tokens,token);
  }
  else {
    attemptShutdown();
  }
}
 
/*
void StateMachine::deleteChild(StateMachine* child) {
//std::cerr << "delete child '" << child->scope->id << "' of '" << scope->id << "'" <<  std::endl;
  if ( child->scope->represents<BPMN::SubProcess>() ) {
//    erase_ptr<StateMachine>(subProcesses, child); /// TODO: check
  }
  else {
    interruptingEventSubProcess.reset();
  }
}
*/
 
void StateMachine::deleteNonInterruptingEventSubProcess(StateMachine* eventSubProcess) {
//std::cerr << "deleteNonInterruptingEventSubProcess" << std::endl;
  erase_ptr<StateMachine>(nonInterruptingEventSubProcesses, eventSubProcess);
  attemptShutdown();
}
 
void StateMachine::deleteCompensationEventSubProcess(StateMachine* eventSubProcess) {
//std::cerr << compensationEventSubProcesses.size() << "deleteCompensationEventSubProcess: " << scope->id << "/" << eventSubProcess->scope->id << "/" << this <<  std::endl;
  erase_ptr<StateMachine>(compensationEventSubProcesses, eventSubProcess);
}
 
void StateMachine::clearObsoleteTokens() {
  for ( auto token : tokens ) {
    token->withdraw();
  }
  tokens.clear();
}
 
void StateMachine::interruptActivity(Token* token) {
//std::cerr << "interrupt activity " << token->node->id << std::endl;
  auto activity = token->node->represents<BPMN::Activity>();
  assert( activity );
 
  if ( activity->loopCharacteristics.has_value() &&
    activity->loopCharacteristics.value() != BPMN::Activity::LoopCharacteristics::Standard
  ) {
    // withdraw all tokens for multi-instance activity
    auto it = const_cast<SystemState*>(systemState)->tokensAtActivityInstance.find(token);
    assert ( it != const_cast<SystemState*>(systemState)->tokensAtActivityInstance.end() );
    for ( auto activeToken : it->second ) {
//std::cerr << "withdraw token at " << activeToken->node->id << "/" << activeToken << std::endl;
      if ( activity->loopCharacteristics.value() == BPMN::Activity::LoopCharacteristics::MultiInstanceSequential ) {
        const_cast<SystemState*>(systemState)->tokenAwaitingMultiInstanceExit.erase(activeToken);
      }
 
      const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.erase(activeToken);
      if ( activity->loopCharacteristics.value() != BPMN::Activity::LoopCharacteristics::MultiInstanceParallel
        || activeToken->state != Token::State::READY
      ) {
        activeToken->withdraw();
      }
      erase_ptr<Token>(tokens, activeToken);
    }
    const_cast<SystemState*>(systemState)->tokensAtActivityInstance.erase(it);
 
    // remove all exit status for multi-instance activity
    const_cast<SystemState*>(systemState)->exitStatusAtActivityInstance.erase(token);
  }
  deleteTokensAwaitingBoundaryEvent(token);
  token->withdraw();
  erase_ptr<Token>(tokens, token);
}
 
void StateMachine::deleteTokensAwaitingBoundaryEvent(Token* token) {
//std::cerr << "deleteTokensAwaitingBoundaryEvent " << token->node->id << std::endl;
  // delete all tokens awaiting boundary event
  auto& tokensAwaitingBoundaryEvent = const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent;
  auto it = tokensAwaitingBoundaryEvent.find(token);
  if ( it != tokensAwaitingBoundaryEvent.end() ) {
    for ( auto waitingToken : it->second ) {
      waitingToken->withdraw();
      erase_ptr<Token>(tokens, waitingToken);
    }
    tokensAwaitingBoundaryEvent.erase(it);
  }
}
 
void StateMachine::registerRecipient() {
  if ( auto it = const_cast<SystemState*>(systemState)->unsent.find((long unsigned int)instance.value());
    it != const_cast<SystemState*>(systemState)->unsent.end()
  ) {
    for ( auto& [message_ptr] : it->second ) {
      if ( auto message = message_ptr.lock() ) {
        const_cast<SystemState*>(systemState)->inbox[this].emplace_back(message->weak_from_this());
        const_cast<SystemState*>(systemState)->outbox[message->origin].emplace_back(message->weak_from_this());
      }
    }
    const_cast<SystemState*>(systemState)->unsent.erase(it);
  }
}
 
void StateMachine::unregisterRecipient() {
//std::cerr << "unregisterRecipient" << std::endl;
  auto eventSubProcess = scope->represents<BPMN::EventSubProcess>();
  if ( 
    !parentToken ||
    ( eventSubProcess && !eventSubProcess->startEvent->isInterrupting )
  ) {
    // delete all messages directed to state machine
    if ( auto it = const_cast<SystemState*>(systemState)->inbox.find(this);
      it != const_cast<SystemState*>(systemState)->inbox.end()
    ) {
      for ( auto& [message_ptr] : it->second ) {
        if ( auto message = message_ptr.lock() ) {
          // withdraw message
          message->state = Message::State::WITHDRAWN;
          systemState->engine->notify(message.get());
          erase_ptr(const_cast<SystemState*>(systemState)->messages, message.get());
        }
      }
      const_cast<SystemState*>(systemState)->inbox.erase(it);
    }
  }
}
 
 
void StateMachine::run(Values status) {
  assert( status.size() >= 1 );
  assert( data.size() >= 1 );
  assert( data[BPMNOS::Model::ExtensionElements::Index::Instance].get().has_value() );
  assert( status[BPMNOS::Model::ExtensionElements::Index::Timestamp].has_value() );
 
//std::cerr << "Run " << scope->id << "/" << this << "/" << parentToken << std::endl;
  if ( !parentToken ) {
    // state machine without parent token represents a process
//std::cerr << "Start process " << process->id << std::endl;
    auto instanceId = (long unsigned int)data[BPMNOS::Model::ExtensionElements::Index::Instance].get().value();
    const_cast<SystemState*>(systemState)->archive[ instanceId ] = weak_from_this();
 
    tokens.push_back( std::make_shared<Token>(this,nullptr,std::move(status)) );
    registerRecipient();
 
    // create child that will own tokens flowing through the process
    createChild(tokens.back().get(),scope, {});
 
  }
  else {
    for ( auto startNode : scope->startNodes ) {
      tokens.push_back( std::make_shared<Token>(this,startNode,std::move(status)) );
    }
  }
 
  for ( auto token : tokens ) {
    if ( token->node ) {
      if ( auto startEvent = token->node->represents<BPMN::TypedStartEvent>() ) {
        // get new attribute values
        auto values = systemState->getStatusAttributes( root, token->node->parent );
        if ( !values.has_value() ) {
          throw std::runtime_error("StateMachine: status of event subprocess '" + token->node->parent->id + "' not known at initialization");
        }
        
        token->status.insert(token->status.end(), values.value().begin(), values.value().end());
 
        if ( !startEvent->isInterrupting ) {
          // token instantiates non-interrupting event subprocess
          // get instantiation counter from context
          auto context = const_cast<StateMachine*>(parentToken->owned.get());
          auto counter = ++context->instantiations[token->node];
          // disambiguate instance id
          auto instanceId = BPMNOS::to_string((*parentToken->data)[BPMNOS::Model::ExtensionElements::Index::Instance].get().value(),STRING) + BPMNOS::Model::Scenario::delimiters[0] + scope->id + BPMNOS::Model::Scenario::delimiters[1] + std::to_string(counter);
          data[BPMNOS::Model::ExtensionElements::Index::Instance].get() = BPMNOS::to_number(instanceId,BPMNOS::ValueType::STRING);
          const_cast<SystemState*>(systemState)->archive[ (long unsigned int)data[BPMNOS::Model::ExtensionElements::Index::Instance].get().value() ] = weak_from_this();
          registerRecipient();
        }
      }
//std::cerr << "Initial token: >" << token->jsonify().dump() << "<" << std::endl;
    }
    // advance token
    token->advanceFromCreated();
  }
}
 
void StateMachine::createChild(Token* parent, const BPMN::Scope* scope, Values data, std::optional<BPMNOS::number> instance) {
//std::cerr << "Create child from " << this << std::endl;
  parent->owned = std::make_shared<StateMachine>(systemState, scope, parent, std::move(data), instance.value_or( (*parent->data)[BPMNOS::Model::ExtensionElements::Index::Instance].get().value() ) );
//  parent->owned->run(parent->status);
}
 
void StateMachine::createCompensationTokenForBoundaryEvent(const BPMN::BoundaryEvent* compensateBoundaryEvent, BPMNOS::Values status) {
  std::shared_ptr<Token> compensationToken = std::make_shared<Token>(this,compensateBoundaryEvent, status);
  compensationToken->update(Token::State::BUSY);
  compensationTokens.push_back(std::move(compensationToken));
}
 
void StateMachine::createCompensationEventSubProcess(const BPMN::EventSubProcess* eventSubProcess, BPMNOS::Values status) {
//std::cerr << "createCompensationEventSubProcess: " << eventSubProcess->id << "/" << scope->id << "/" << parentToken->owner->scope->id <<std::endl;
  // create state machine for compensation event subprocess
  auto data = systemState->getDataAttributes(root,eventSubProcess);
  if ( !data.has_value() ) {
    throw std::runtime_error("StateMachine: required data at '" + eventSubProcess->id +"' not yet available" );
  }
  compensationEventSubProcesses.push_back(std::make_shared<StateMachine>( systemState, eventSubProcess, parentToken, std::move(data.value()) ) );
  // create token at start event of compensation event subprocess
  std::shared_ptr<Token> compensationToken = std::make_shared<Token>(compensationEventSubProcesses.back().get(), eventSubProcess->startEvent, status );
  compensationToken->update(Token::State::BUSY);
  compensationTokens.push_back(std::move(compensationToken));
}
 
void StateMachine::compensateActivity(Token* token) {
  auto compensationNode = token->node->as<BPMN::BoundaryEvent>()->attachedTo->compensatedBy;
//std::cerr << "compensationNode: " << compensationNode->id << std::endl;
  assert( compensationNode != nullptr );
  if ( auto compensationActivity = compensationNode->represents<BPMN::Activity>() ) {
    // move token to compensation activity
    token->node = compensationActivity;
    auto engine = const_cast<Engine*>(systemState->engine);
    if ( auto scope = token->node->represents<BPMN::Scope>() ) {
      auto data = systemState->getDataAttributes(root,token->node);
      if ( !data.has_value() ) {
        throw std::runtime_error("StateMachine: required data at '" + token->node->id +"' not yet available" );
      }
      createChild( token, scope, std::move(data.value()) );
    }
    engine->commands.emplace_back(std::bind(&Token::advanceToEntered,token), token);
  }
}
 
std::vector<Token*> StateMachine::createTokenCopies(Token* token, const std::vector<BPMN::SequenceFlow*>& sequenceFlows) {
  std::vector<Token*> tokenCopies;
  // create a token copy for each new destination
  for ( [[maybe_unused]] auto _ : sequenceFlows ) {
    tokens.push_back( std::make_shared<Token>( token ) );
    tokenCopies.push_back(tokens.back().get());
  }
 
  // advance all token copies
  for (size_t i = 0; i < sequenceFlows.size(); i++ ) {
    auto tokenCopy = tokenCopies[i];
    auto engine = const_cast<Engine*>(systemState->engine);
    engine->commands.emplace_back(std::bind(&Token::advanceToDeparted,tokenCopy,sequenceFlows[i]), tokenCopy);
  }
  return tokenCopies;
}
 
void StateMachine::createMergedToken(const BPMN::FlowNode* gateway) {
  auto gatewayIt = const_cast<SystemState*>(systemState)->tokensAwaitingGatewayActivation[this].find(gateway);
  auto& [key,arrivedTokens] = *gatewayIt;
 
  // create merged token
  std::shared_ptr<Token> mergedToken = std::make_shared<Token>(arrivedTokens);
 
  // remove tokens
  for ( auto arrivedToken : arrivedTokens ) {
    erase_ptr<Token>(tokens,arrivedToken);
  }
  const_cast<SystemState*>(systemState)->tokensAwaitingGatewayActivation[this].erase(gatewayIt);
 
  // add merged token
  tokens.push_back(std::move(mergedToken));
 
  // advance merged token
  auto token = tokens.back().get();
  auto engine = const_cast<Engine*>(systemState->engine);
  engine->commands.emplace_back(std::bind(&Token::advanceToEntered,token), token);
}
 
 
void StateMachine::handleDivergingGateway(Token* token) {
  if ( token->node->represents<BPMN::ParallelGateway>() ) {
    // create token copies and advance them
    createTokenCopies(token, token->node->outgoing);
    // remove original token
    erase_ptr<Token>(tokens,token);
  }
  else if ( token->node->represents<BPMN::EventBasedGateway>() ) {
    // create token copies and advance them
    auto tokenCopies = createTokenCopies(token, token->node->outgoing);
    auto& tokenAtEventBasedGateway = const_cast<SystemState*>(systemState)->tokenAtEventBasedGateway;
    auto& tokensAwaitingEvent = const_cast<SystemState*>(systemState)->tokensAwaitingEvent;
 
    for ( auto tokenCopy : tokenCopies ) {
      tokenAtEventBasedGateway[tokenCopy] = token;
      tokensAwaitingEvent[token].push_back(tokenCopy);
    }
  }
  else {
    throw std::runtime_error("StateMachine: diverging gateway type of node '" + token->node->id + "' not yet supported");
  }
}
 
void StateMachine::handleEventBasedGatewayActivation(Token* token) {
  auto tokenAtEventBasedGateway = const_cast<SystemState*>(systemState)->tokenAtEventBasedGateway.at(token);
  auto waitingTokens = const_cast<SystemState*>(systemState)->tokensAwaitingEvent.at(tokenAtEventBasedGateway);
  // remove all other waiting tokens
  for ( auto waitingToken : waitingTokens ) {
    if ( waitingToken != token ) {
      waitingToken->withdraw();
      erase_ptr<Token>(tokens,waitingToken);
    }
  }
  // remove token at event-based gateway
  tokenAtEventBasedGateway->update(Token::State::COMPLETED);
  erase_ptr<Token>(tokens,tokenAtEventBasedGateway);
}
 
void StateMachine::handleEscalation(Token* token) {
//std::cerr << "handleEscalation " << (token->node ? token->node->id : process->id ) << std::endl;
  if ( !parentToken ) {
    return;
  }
 
  auto it = std::find_if(pendingEventSubProcesses.begin(), pendingEventSubProcesses.end(), [](std::shared_ptr<StateMachine>& stateMachine) {
    auto eventSubProcess = stateMachine->scope->as<BPMN::EventSubProcess>();
    return eventSubProcess->startEvent->represents<BPMN::EscalationStartEvent>();
  });
 
  auto engine = const_cast<Engine*>(systemState->engine);
 
  if ( it != pendingEventSubProcesses.end() ) {
    // trigger event subprocess
    auto eventToken = it->get()->tokens.front().get();
//std::cerr << "found event-subprocess catching escalation:" << eventToken << "/" << eventToken->owner << std::endl;
    eventToken->status = token->status;
    eventToken->advanceToCompleted();
 
    return;
  }
 
  if ( auto activity = token->node->represents<BPMN::Activity>();
    activity &&
    token->state != Token::State::WAITING &&
    activity->loopCharacteristics.has_value() &&
    activity->loopCharacteristics.value() != BPMN::Activity::LoopCharacteristics::Standard
  ) {
    // handle failure at main token waiting for all instances
    auto mainToken = const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.at(token);
    mainToken->status = token->status;
    handleEscalation(mainToken);
    return;
  }
 
  // find escalation boundary event
  if ( token->node ) {
    auto& tokensAwaitingBoundaryEvent = const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent[token];
    for ( auto eventToken : tokensAwaitingBoundaryEvent) {
      if ( eventToken->node->represents<BPMN::EscalationBoundaryEvent>() ) {
        eventToken->status = token->status;
        eventToken->advanceToCompleted();
        return;
      }
    }
  }
 
  // update status of parent token with that of current token
  parentToken->status = token->status;
  parentToken->update(parentToken->state);
 
//std::cerr << "bubbble up escalation" << std::endl;
  auto parent = const_cast<StateMachine*>(parentToken->owner);
  engine->commands.emplace_back(std::bind(&StateMachine::handleEscalation,parent,parentToken), parentToken);
 
}
 
void StateMachine::handleFailure(Token* token) {
//std::cerr << scope->id << " handles failure at " << (token->node ? token->node->id : process->id ) << "/" << parentToken << "/" << token << std::endl;
  auto engine = const_cast<Engine*>(systemState->engine);
 
//  assert( !token->owned );
 
//std::cerr << "check whether failure is caught" << std::endl;
 
  if ( token->node ) {
    if ( auto activity = token->node->represents<BPMN::Activity>() ) {
      if ( activity->isForCompensation ) {
        // compensation activity failed, clear all other compensations
        compensationTokens.clear();
      }
      else if ( token->state != Token::State::WAITING &&
        activity->loopCharacteristics.has_value() &&
        activity->loopCharacteristics.value() != BPMN::Activity::LoopCharacteristics::Standard
      ) {
        // handle failure at main token waiting for all instances       
        auto mainToken = const_cast<SystemState*>(systemState)->tokenAtMultiInstanceActivity.at(token);
//std::cerr << "handle failure at main token waiting for all instances "  << std::endl;
        mainToken->status = token->status;
        handleFailure(mainToken);
        return;
      }
    }
  }
 
  // find error boundary event at token node
  if ( token->node ) {
    auto& tokensAwaitingBoundaryEvent = const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent[token];
    for ( auto eventToken : tokensAwaitingBoundaryEvent) {
      if ( eventToken->node->represents<BPMN::ErrorBoundaryEvent>() ) {
        eventToken->status = token->status;
        eventToken->advanceToCompleted();
        return;
      }
    }
  }
 
  // find event-subprocess catching error
  auto it = std::find_if(pendingEventSubProcesses.begin(), pendingEventSubProcesses.end(), [](std::shared_ptr<StateMachine>& stateMachine) {
    auto eventSubProcess = stateMachine->scope->as<BPMN::EventSubProcess>();
    return eventSubProcess->startEvent->represents<BPMN::ErrorStartEvent>();
  });
  if ( it != pendingEventSubProcesses.end() ) {
    // trigger event subprocess
    auto eventToken = it->get()->tokens.front().get();
    // update status of event token with that of current token
    eventToken->status = token->status;
    // remove all tokens
    clearObsoleteTokens();
    engine->commands.emplace_back(std::bind(&Token::advanceToCompleted,eventToken), eventToken);
 
    return;
  }
 
  // failure is not caught
//std::cerr << "uncaught failure" << std::endl;
 
  
  if ( !parentToken ) {
//std::cerr << "process has failed" << std::endl;
    // failure at process before state machine containing flow elements has been created
    assert(tokens.size() == 1);
    assert(token = tokens.front().get());
    engine->commands.emplace_back(std::bind(&Engine::deleteInstance,engine,this), this);
    return;
  }
  
  // bubble up error
  
  // update status of parent token with that of current token
  parentToken->status = token->status;
  engine->commands.emplace_back(std::bind(&Token::advanceToFailed,parentToken), parentToken);
}
 
Token* StateMachine::findTokenAwaitingErrorBoundaryEvent(Token* activityToken) {
  auto& tokensAwaitingBoundaryEvent = const_cast<SystemState*>(systemState)->tokensAwaitingBoundaryEvent[activityToken];
  for ( auto eventToken : tokensAwaitingBoundaryEvent) {
    if ( eventToken->node->represents<BPMN::ErrorBoundaryEvent>() ) {
      return eventToken;
    }
  }
  return nullptr;
}
 
void StateMachine::attemptGatewayActivation(const BPMN::FlowNode* node) {
  if ( node->represents<BPMN::ParallelGateway>() ) {
 
    auto gatewayIt = const_cast<SystemState*>(systemState)->tokensAwaitingGatewayActivation[this].find(node);
    auto& [key,arrivedTokens] = *gatewayIt;
    if ( arrivedTokens.size() == node->incoming.size() ) {
      // create merged token and advance it
      auto engine = const_cast<Engine*>(systemState->engine);
      engine->commands.emplace_back(std::bind(&StateMachine::createMergedToken,this,node), this);
    }
  }
  else {
    throw std::runtime_error("StateMachine: converging gateway type of node '" + node->id + "' not yet supported");
  }
}
 
void StateMachine::shutdown() {
  auto engine = const_cast<Engine*>(systemState->engine);
//std::cerr << "shutdown: " << scope->id << std::endl;
  assert( tokens.size() );
  BPMNOS::Values mergedStatus = Token::mergeStatus(tokens);
  
  if ( auto eventSubProcess = scope->represents<BPMN::EventSubProcess>() ) {
    // update global objective
    assert( scope->extensionElements->as<BPMNOS::Model::ExtensionElements>() );
    const_cast<SystemState*>(systemState)->contributionsToObjective += scope->extensionElements->as<BPMNOS::Model::ExtensionElements>()->getContributionToObjective(mergedStatus,data,parentToken->globals);
 
    if (!eventSubProcess->startEvent->isInterrupting ) {
      // delete non-interrupting event subprocess
      auto context = const_cast<StateMachine*>(parentToken->owned.get());
      engine->commands.emplace_back(std::bind(&StateMachine::deleteNonInterruptingEventSubProcess,context,this), this);
      return;
    }
    else if ( eventSubProcess->startEvent->represents<BPMN::CompensateStartEvent>() ) {
      completeCompensationEventSubProcess();
      return;
    }
  }
 
//std::cerr << "start shutdown: " << BPMNOS::to_string(instance.value(),STRING) << std::endl;
 
  // update status of parent token (if it doesn't have a sequential performer)
  if ( parentToken &&
    !scope->extensionElements->as<BPMNOS::Model::ExtensionElements>()->hasSequentialPerformer
  ) {
    parentToken->status = mergedStatus;
  }
  tokens.clear();
 
  // ensure that messages to state machine are removed  
  unregisterRecipient();
  
  if ( auto subProcess = scope->represents<BPMN::SubProcess>();
    subProcess && subProcess->compensatedBy
  ) {
    if ( subProcess->compensatedBy->represents<BPMN::EventSubProcess>() ) {
      auto parent = const_cast<StateMachine*>(parentToken->owner);
      // move state machine pointer to ensure it is not deleted
      parent->compensableSubProcesses.push_back(shared_from_this());
    }
  }
 
  if ( !parentToken ) {
//std::cerr << "delete root: " << BPMNOS::to_string(instance.value(),STRING) << std::endl;
    // delete root state machine (and all descendants)
    engine->commands.emplace_back(std::bind(&Engine::deleteInstance,engine,this), this);
  }
  else {
//std::cerr << "delete child: " << scope->id << std::endl;
    auto parent = const_cast<StateMachine*>(parentToken->owner);
    if ( auto eventSubProcess = scope->represents<BPMN::EventSubProcess>();
      eventSubProcess && eventSubProcess->startEvent->isInterrupting
    ) {
      parent->interruptingEventSubProcess.reset();
    }
//    engine->commands.emplace_back(std::bind(&StateMachine::deleteChild,parent,this), this);
 
    // advance parent token to completed
    auto context = const_cast<StateMachine*>(parentToken->owned.get());
    auto token = context->parentToken;
    engine->commands.emplace_back(std::bind(&Token::advanceToCompleted,token), token);
  }
 
//std::cerr << "shutdown (done): " << scope->id <<std::endl;
}
 
void StateMachine::attemptShutdown() {
//std::cerr << "attemptShutdown: " << scope->id << "/" << this << std::endl;
  if ( interruptingEventSubProcess ) {
//std::cerr << "wait for completion of interrupting event subprocess" << interruptingEventSubProcess->scope->id << std::endl;
    // wait for completion of interrupting event subprocess
    return;
  }
 
  for ( auto& token : tokens ) {
    if ( token->state != Token::State::DONE ) {
      return;
    }
  }
 
  // all tokens are in DONE state
 
  // no new event subprocesses can be triggered
  for ( auto eventSubProcess : pendingEventSubProcesses ) {
    eventSubProcess->clearObsoleteTokens();
  }
  pendingEventSubProcesses.clear();
 
  if ( nonInterruptingEventSubProcesses.size() ) {
    // wait until last event subprocess is completed
    return;
  }
 
  auto engine = const_cast<Engine*>(systemState->engine);
//std::cerr << "Shutdown with " << engine->commands.size() << " prior commands" << std::endl;
  engine->commands.emplace_back(std::bind(&StateMachine::shutdown,this), this);
}
 
Tokens StateMachine::getCompensationTokens(const BPMN::Activity* activity) const {
//std::cerr << scope->id << " getCompensationTokens of " << ( activity ? activity->id : std::string("all activities") )  << std::endl; 
  Tokens result;
  if ( compensationTokens.empty() ) {
//std::cerr << "no compensation token" << std::endl;
    return result;
  }
 
  if ( activity ) {
    // find compensation within context
    auto it = std::find_if(
       compensationTokens.begin(),
       compensationTokens.end(),
       [&activity](const std::shared_ptr<Token>& token) -> bool {
         // check if compensation token is at compensation boundary event
         return ( token.get()->node->as<BPMN::BoundaryEvent>()->attachedTo == activity );
       }
    );
    if ( it != compensationTokens.end() ) {
      result.push_back(*it);
    }
  }
  else {
    result = compensationTokens;
  }
 
//std::cerr << "compensating " << result.size() << " tokens" << std::endl;
  return result;
}
 
 
void StateMachine::advanceTokenWaitingForCompensation(Token* waitingToken) {
//std::cerr << scope->id << " -> advanceTokenWaitingForCompensation: " << waitingToken->node->id << "/" << Token::stateName[(int)waitingToken->state]<< "/" << waitingToken << std::endl;
  auto engine = const_cast<Engine*>(systemState->engine);
  if ( waitingToken->state == Token::State::BUSY ) {
 
    // erase from compensation tokens and move to tokens
    if ( waitingToken->node->represents<BPMN::CompensateBoundaryEvent>() ) {
      tokens.emplace_back(waitingToken->shared_from_this());
      erase_ptr<Token>(compensationTokens,waitingToken);
    }
    else if ( waitingToken->node->represents<BPMN::CompensateStartEvent>() ) {
      const_cast<StateMachine*>(waitingToken->owner)->tokens.emplace_back(waitingToken->shared_from_this());
      erase_ptr<Token>(compensationTokens,waitingToken);
    } 
 
//std::cerr << "Continue with advanceToCompleted: " << waitingToken->node->id << std::endl;
    engine->commands.emplace_back(std::bind(&Token::advanceToCompleted,waitingToken), waitingToken);
  }
  else if ( waitingToken->state == Token::State::FAILING ) {
//std::cerr << "Continue with terminate: " << waitingToken->owner->scope->id << std::endl;
    assert( waitingToken->owner == this);
//    engine->commands.emplace_back(std::bind(&StateMachine::terminate,this), this);
    engine->commands.emplace_back(std::bind(&StateMachine::handleFailure,this,waitingToken), waitingToken);
  }
  else {
//  std::cerr << waitingToken->node->id << " has state: " << Token::stateName[(int)waitingToken->state]  << std::endl;
    assert(!"unexpected state of waiting token");
  }
}
 
void StateMachine::completeCompensationActivity(Token* token) {
  // token is still the compensation token
 
  // advance waiting token
  auto& tokenAwaitingCompensationActivity = const_cast<SystemState*>(systemState)->tokenAwaitingCompensationActivity;
  auto waitingToken = tokenAwaitingCompensationActivity.at(token);
  const_cast<StateMachine*>(waitingToken->owner)->advanceTokenWaitingForCompensation( waitingToken );
  tokenAwaitingCompensationActivity.erase(token);
 
  // remove token
//std::cerr << scope->id  << " -> Compensation completed: " << token->node->id << "/" << token << "/" << tokens.size() << "/" << compensationTokens.size() << std::endl;
  erase_ptr<Token>(tokens,token);
}
 
void StateMachine::completeCompensationEventSubProcess() {
  auto& tokenAwaitingCompensationEventSubProcess = const_cast<SystemState*>(systemState)->tokenAwaitingCompensationEventSubProcess;
  auto waitingToken = tokenAwaitingCompensationEventSubProcess.at(this);
  const_cast<StateMachine*>(waitingToken->owner)->advanceTokenWaitingForCompensation( waitingToken );
  tokenAwaitingCompensationEventSubProcess.erase(this);
  auto engine = const_cast<Engine*>(systemState->engine);
  // erase state machine
  auto context = const_cast<StateMachine*>(parentToken->owned.get());
  engine->commands.emplace_back(std::bind(&StateMachine::deleteCompensationEventSubProcess,context,this), this);
}
 
 
void StateMachine::compensate(Tokens compensations, Token* waitingToken) {
//std::cerr << "\ncompensate: " << scope->id << " compensate " <<  compensations.size() << " tokens before continuing with " << waitingToken->node->id << std::endl;
 
  auto engine = const_cast<Engine*>(systemState->engine);
  auto& tokenAwaitingCompensationActivity = const_cast<SystemState*>(systemState)->tokenAwaitingCompensationActivity;
  auto& tokenAwaitingCompensationEventSubProcess = const_cast<SystemState*>(systemState)->tokenAwaitingCompensationEventSubProcess;
 
  auto it = compensations.rbegin();
  // advance last compensation token
  auto compensationToken = it->get();
 
  if ( compensationToken->node->represents<BPMN::CompensateStartEvent>() ) {
    const_cast<StateMachine*>(compensationToken->owner)->tokens.push_back(std::move(*it));
  }
  else {
    tokens.push_back(std::move(*it));
  }
//std::cerr << engine->commands.size() <<" Compensate " << compensationToken->node->id << "/scope: " << compensationToken->owner->scope->id << std::endl;
 
  // erase compensation token and move to active tokens
  erase_ptr<Token>(compensationTokens,compensationToken);
 
  engine->commands.emplace_back(std::bind(&Token::advanceToCompleted,compensationToken), compensationToken);
 
  // go to next compensation token
  it++;
  while ( it != compensations.rend() ) {
//std::cerr << engine->commands.size() <<"+Compensate " << compensationToken->node->id << "/scope: " << compensationToken->owner->scope->id << std::endl;
    // create awaiters for all other compensations
    if ( compensationToken->node->represents<BPMN::CompensateStartEvent>() ) {
      tokenAwaitingCompensationEventSubProcess[const_cast<StateMachine*>(compensationToken->owner)] = it->get();
    }
    else {
      tokenAwaitingCompensationActivity[compensationToken] = it->get();
    }
    compensationToken = it->get();
    it++;
  }
  // create awaiter for waiting token
  if ( compensationToken->node->represents<BPMN::CompensateStartEvent>() ) {
    tokenAwaitingCompensationEventSubProcess[const_cast<StateMachine*>(compensationToken->owner)] = waitingToken;
  }
  else {
    tokenAwaitingCompensationActivity[compensationToken] = waitingToken;
  }
}