/**
 * \class QgsLegendInterface
 * \brief Abstract base class to make QgsLegend available to plugins.
 */
class QgsLegendInterface : QObject
{
%TypeHeaderCode
#include <qgslegendinterface.h>
%End

  public:

    /** Constructor */
    QgsLegendInterface();

    /** Virtual destructor */
    ~QgsLegendInterface();

    //! Return a string list of groups
    virtual QStringList groups() = 0;

    //! Return the relationship between groups and layers in the legend
    virtual QList< QPair< QString, QList<QString> > > groupLayerRelationship();

    //! Returns the currently selected layers of QgsLegendLayers.
    //! @param inDrawOrder return layers in drawing order (added in 1.9)
    //! @returns list of layers, else an empty list
    virtual QList<QgsMapLayer *> selectedLayers( bool inDrawOrder = false ) const = 0;

    //! Return all layers in the project in drawing order
    //! @note added in 1.5
    virtual QList< QgsMapLayer * > layers() const = 0;

    //! Check if a group exists
    //! @note added in 1.5
    virtual bool groupExists( int groupIndex ) = 0;

    //! Check if a group is expanded
    //! @note added in 1.5
    virtual bool isGroupExpanded( int groupIndex ) = 0;

    //! Check if a group is visible
    //! @note added in 1.5
    virtual bool isGroupVisible( int groupIndex ) = 0;

    //! Check if a layer is expanded
    //! @note added in 2.0
    virtual bool isLayerExpanded( QgsMapLayer * ml ) = 0;

    //! Check if a layer is visible
    //! @note added in 1.5
    virtual bool isLayerVisible( QgsMapLayer * ml ) = 0;

    /** Add action for layers in the legend
     * @note added in 2.0
     */
    virtual void addLegendLayerAction( QAction* action, QString menu, QString id,
                                       QgsMapLayer::LayerType type, bool allLayers ) = 0;

    /** Add action for a specific layers in the legend.
     * Use this in combination with addLegendLayerAction( allLayers = False )
     * @note added in 2.0
     */
    virtual void addLegendLayerActionForLayer( QAction* action, QgsMapLayer* layer ) = 0;

    /** Remove action for layers in the legend
     * @note added in 2.0
     */
    virtual bool removeLegendLayerAction( QAction* action ) = 0;

    //! Returns the current layer if the current item is a QgsLegendLayer.
    //! If the current item is a QgsLegendLayer, its first maplayer is returned.
    //! Else, 0 is returned.
    //! @note Added in 2.0
    virtual QgsMapLayer* currentLayer() = 0;

    //! set the current layer
    //! returns true if the layer exists, false otherwise
    //! @note Added in 2.0
    virtual bool setCurrentLayer( QgsMapLayer *layer ) = 0;

  signals:

    //! emitted when a group index has changed
    void groupIndexChanged( int oldIndex, int newIndex );

    /* //! emitted when group relations have changed */
    void groupRelationsChanged( );

    /* //! emitted when an item (group/layer) is added */
    void itemAdded( QModelIndex index );

    /* //! emitted when an item (group/layer) is removed */
    void itemRemoved( );

    //! Emitted whenever current (selected) layer changes
    //  the pointer to layer can be null if no layer is selected
    //! @note Added in 2.0
    void currentLayerChanged( QgsMapLayer * layer );

  public slots:

    //! Add a new group
    //! a parent group can be given to nest the new group in it
    virtual int addGroup( QString name, bool expand = true, QTreeWidgetItem* parent = 0 ) = 0;

    //! Add a new group
    //! a parent group index has to be given to nest the new group in it
    virtual int addGroup( QString name, bool expand, int parentIndex ) = 0;

    //! Remove group on index
    virtual void removeGroup( int groupIndex ) = 0;

    //! Move a layer to a group
    virtual void moveLayer( QgsMapLayer * ml, int groupIndex ) = 0;

    //! Collapse or expand a group
    //! @note added in 1.5
    virtual void setGroupExpanded( int groupIndex, bool expand ) = 0;

    //! Collapse or expand a layer
    //! @note added in 2.0
    virtual void setLayerExpanded( QgsMapLayer * ml, bool expand ) = 0;

    //! Set the visibility of a group
    //! @note added in 1.5
    virtual void setGroupVisible( int groupIndex, bool visible ) = 0;

    //! Set the visibility of a layer
    //! @note added in 1.5
    virtual void setLayerVisible( QgsMapLayer * ml, bool visible ) = 0;

    //! Refresh layer symbology
    //! @note added in 1.5
    virtual void refreshLayerSymbology( QgsMapLayer *ml ) = 0;
};