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  //
  //  W A R N I N G
  //  -------------
  //
  // This file is not part of the Qt API.  It exists purely as an
  // implementation detail.  This header file may change from version to
  // version without notice, or even be removed.
  //
  // We mean it.
  
  #ifndef Patternist_XsdStateMachine_H
  #define Patternist_XsdStateMachine_H
  
  #include <private/qnamepool_p.h>
  
  #include <QtCore/QHash>
  #include <QtCore/QSet>
  #include <QtCore/QTextStream>
  
  QT_BEGIN_NAMESPACE
  
  class QIODevice;
  
  namespace QPatternist
  {
      /**
       * @short A state machine used for evaluation.
       *
       * @ingroup Patternist_schema
       * @author Tobias Koenig <tobias.koenig@nokia.com>
       */
      template <typename TransitionType>
      class XsdStateMachine
      {
          public:
              typedef qint32 StateId;
  
              /**
               * Describes the type of state.
               */
              enum StateType
              {
                  StartState,     ///< The state the machine will start with.
                  StartEndState,  ///< The state the machine will start with, can be end state as well.
                  InternalState,  ///< Any state that is not start or end state.
                  EndState        ///< Any state where the machine is allowed to stop.
              };
  
              /**
               * Creates a new state machine object.
               */
              XsdStateMachine();
  
              /**
               * Creates a new state machine object.
               *
               * The name pool to use for accessing object names.
               */
              XsdStateMachine(const NamePool::Ptr &namePool);
  
              /**
               * Adds a new state of the given @p type to the state machine.
               *
               * @return The id of the new state.
               */
              StateId addState(StateType type);
  
              /**
               * Adds a new @p transition to the state machine.
               *
               * @param start The start state.
               * @param transition The transition to come from the start to the end state.
               * @param end The end state.
               */
              void addTransition(StateId start, TransitionType transition, StateId end);
  
              /**
               * Adds a new epsilon @p transition to the state machine.
               *
               * @param start The start state.
               * @param end The end state.
               */
              void addEpsilonTransition(StateId start, StateId end);
  
              /**
               * Resets the machine to the start state.
               */
              void reset();
  
              /**
               * Removes all states and transitions from the state machine.
               */
              void clear();
  
              /**
               * Continues execution of the machine with the given input @p transition.
               *
               * @return @c true if the transition was successful, @c false otherwise.
               */
              bool proceed(TransitionType transition);
  
              /**
               * Returns the list of transitions that are reachable from the current
               * state.
               */
              QList<TransitionType> possibleTransitions() const;
  
              /**
               * Continues execution of the machine with the given @p input.
               *
               * @note To use this method, inputEqualsTransition must be implemented
               *       to find the right transition to use.
               *
               * @return @c true if the transition was successful, @c false otherwise.
               */
              template <typename InputType>
              bool proceed(InputType input);
  
              /**
               * Returns whether the given @p input matches the given @p transition.
               */
              template <typename InputType>
              bool inputEqualsTransition(InputType input, TransitionType transition) const;
  
              /**
               * Returns whether the machine is in an allowed end state.
               */
              bool inEndState() const;
  
              /**
               * Returns the last transition that was taken.
               */
              TransitionType lastTransition() const;
  
              /**
               * Returns the start state of the machine.
               */
              StateId startState() const;
  
              /**
               * This method should be redefined by template specialization for every
               * concret TransitionType.
               */
              QString transitionTypeToString(TransitionType type) const;
  
              /**
               * Outputs the state machine in DOT format to the given
               * output @p device.
               */
              bool outputGraph(QIODevice *device, const QString &graphName) const;
  
              /**
               * Returns a DFA that is equal to the NFA of the state machine.
               */
              XsdStateMachine<TransitionType> toDFA() const;
  
              /**
               * Returns the information of all states of the state machine.
               */
              QHash<StateId, StateType> states() const;
  
              /**
               * Returns the information of all transitions of the state machine.
               */
              QHash<StateId, QHash<TransitionType, QVector<StateId> > > transitions() const;
  
          private:
              /**
               * Returns the DFA state for the given @p nfaStat from the given @p stateTable.
               * If there is no corresponding DFA state yet, a new one is created.
               */
              StateId dfaStateForNfaState(QSet<StateId> nfaState, QList< QPair< QSet<StateId>, StateId> > &stateTable, XsdStateMachine<TransitionType> &dfa) const;
  
              /**
               * Returns the set of all states that can be reached from the set of @p input states
               * by the epsilon transition.
               *
               * The implementation is inlined in order to workaround a compiler
               * bug on Symbian/winscw.
               */
              QSet<StateId> epsilonClosure(const QSet<StateId> &input) const
              {
                  // every state can reach itself by epsilon transition, so include the input states
                  // in the result as well
                  QSet<StateId> result = input;
  
                  // add the input states to the list of to be processed states
                  QList<StateId> workStates = input.values();
                  while (!workStates.isEmpty()) { // while there are states to be processed left...
  
                      // dequeue one state from list
                      const StateId state = workStates.takeFirst();
  
                      // get the list of states that can be reached by the epsilon transition
                      // from the current 'state'
                      const QVector<StateId> targetStates = m_epsilonTransitions.value(state);
                      for (int i = 0; i < targetStates.count(); ++i) {
                          // if we have this target state not in our result set yet...
                          if (!result.contains(targetStates.at(i))) {
                              // ... add it to the result set
                              result.insert(targetStates.at(i));
  
                              // add the target state to the list of to be processed states as well,
                              // as we want to have the epsilon transitions not only for the first
                              // level of following states
                              workStates.append(targetStates.at(i));
                          }
                      }
                  }
  
                  return result;
              }
  
              /**
               * Returns the set of all states that can be reached from the set of given @p states
               * by the given @p input.
               *
               * The implementation is inlined in order to workaround a compiler
               * bug on Symbian/winscw.
               */
              QSet<StateId> move(const QSet<StateId> &states, TransitionType input) const
              {
                  QSet<StateId> result;
  
                  for (const StateId state : states) {
  
                      // get the transition table for the current state
                      const QHash<TransitionType, QVector<StateId> > transitions = m_transitions.value(state);
  
                      // get the target states for the given input
                      const QVector<StateId> targetStates = transitions.value(input);
  
                      // add all target states to the result
                      for (int i = 0; i < targetStates.size(); ++i)
                          result.insert(targetStates.at(i));
                  }
  
                  return result;
              }
  
              NamePool::Ptr                                             m_namePool;
              QHash<StateId, StateType>                                 m_states;
              QHash<StateId, QHash<TransitionType, QVector<StateId> > > m_transitions;
              QHash<StateId, QVector<StateId> >                         m_epsilonTransitions;
              StateId                                                   m_currentState;
              qint32                                                    m_counter;
              TransitionType                                            m_lastTransition;
      };
  
      #include "qxsdstatemachine_tpl_p.h"
  }
  
  QT_END_NAMESPACE
  
  #endif
  