/*

* Copyright (c) 2009-2010 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:

*

*/

#ifndef CXESTATEMACHINEBASE_H

#define CXESTATEMACHINEBASE_H

#include <QHash>

#include <QString>

#include "cxeerror.h"

class CxeState;

/**

* CxeStateMachineBase is used as the base class for all finite state machines in the

* engine. It's not a fully functional state machine in the sense that it does not provide any

* mechanism for handling events that would trigged state changes. Instead,

* it relies on the derived class to call setState() whenever the state

* should change. The derived class should also provide a list of states

* and allowed transitions so that CxeStateMachineBase can verify that each state

* change is valid. A pure virtual function, handleStateChanged() should be

* implemented by derived classes to handle notifing other interested objects about

* the state change. This class cannot emit the signals itself, because it does not

* derived from QObject and it handles all state IDs as plain integers instead of the

* preferred class specific enumerations.

*

* CxeStateMachineBase does not derive from QObject to make easier for the engine

* control implementation classes to derive from it. Additionally we avoid the overhead

* brought by QObject.

*

* CxeStateMachineBase class is to be used for unit testing. Engine class should derive

* from CxeStateMachine class.

*/

class CxeStateMachineBase

{

public:

    /**

    * CxeStateMachine constructor.

    * @sa addState setInitialState

    * @param stateMachineName  Name for this state machine (used for debug prints)

    */

    CxeStateMachineBase(const char *stateMachineName);

    virtual ~CxeStateMachineBase();

protected:

    /**

     * Add a new state to the machine. Takes ownership of state.

     *

     * @param state A CxeState object defining a name, ID, and allowed transitions for the

     * new state. The CxeState ID must be unique and not to contain overlapping bits with other

     * state ids, since bitwise AND operator is used for the state ids.

     * @return False if adding failed due to incorrect id.

     */

    virtual bool addState(CxeState *state);

    /**

     * Initiate a state transition from current state to a given state ID. In cases that

     * current state is same as the new state, method returns without doing anything. If the state

     * transition is invalid, this function return false.

     *

     * @param stateId State ID of the new state

     * @param error   Optional error code to be associated with the transition

     * @return False if state change fails. True if changing is allowed, or the current state is same

     * as the new state.

     */

    virtual bool setState(int stateId, CxeError::Id error = CxeError::None);

    /**

     * Set the initial state of the state machine. Can be called only once.

     * This method will panic, if initial state is unknown, or initial state has already

     * been set.

     *

     * @param stateId State ID for the initial state.

     * @return False if state to be set intial state is not known, or initial

     * state has already been set.

     */

    virtual bool setInitialState(int stateId);

    /**

     * Pure virtual function to be implemented by derived classes. Called when state changes.

     * The implementation should emit a signal informing interested parties of a state change.

     *

     * @param newStateId State ID for the new state

     * @param error      An error code associated with the state transition

     */

    virtual void handleStateChanged(int newStateId, CxeError::Id error) = 0;

    /**

     * Get current state ID. It is recommended for derived classes to create

     * a new method (typically called state()) which returns the current state ID

     * typecasted into a class specific enumeration.

     * @return Current state ID

     */

    int stateId() const;

    /**

     * Verify if a state transition is possible.

     * @param newStateId  State ID of the new state.

     * @return Whether state transition is possible.

     */

    bool verifyStateChange(int newStateId);

private:

    //! Hash table of all states. stateId as key

    QHash<int, CxeState *> mStates;

    //! All states ORed together

    int mStateBitsUsed;

    //! Current state

    int mStateId;

    //! Name of this state machine (for debug prints)

    QString mName;

};

#endif // CXESTATEMACHINEBASE_H