/**
 * The QgsLayerTreeView class extends QTreeView and provides some additional functionality
 * when working with a layer tree.
 *
 * The view updates expanded state of layer tree nodes and also listens to changes
 * to expanded states in the layer tree.
 *
 * The view keeps track of the current layer and emits a signal when the current layer has changed.
 *
 * Allows the client to specify a context menu provider with custom actions. Also it comes
 * with a set of default actions that can be used when building context menu.
 *
 * @see QgsLayerTreeModel
 * @note added in 2.4
 */
class QgsLayerTreeView : QTreeView
{
%TypeHeaderCode
#include <qgslayertreeview.h>
%End

%ConvertToSubClassCode
  if (sipCpp->inherits("QgsLayerTreeView"))
    sipType = sipType_QgsLayerTreeView;
  else
    sipType = 0;
%End

  public:
    explicit QgsLayerTreeView( QWidget *parent /TransferThis/ = 0 );
    ~QgsLayerTreeView();

    //! Overridden setModel() from base class. Only QgsLayerTreeModel is an acceptable model.
    virtual void setModel( QAbstractItemModel *model );

    //! Get access to the model casted to QgsLayerTreeModel
    QgsLayerTreeModel *layerTreeModel() const;

    //! Get access to the default actions that may be used with the tree view
    QgsLayerTreeViewDefaultActions *defaultActions();

    //! Set provider for context menu. Takes ownership of the instance
    void setMenuProvider( QgsLayerTreeViewMenuProvider *menuProvider /Transfer/ );
    //! Return pointer to the context menu provider. May be null
    QgsLayerTreeViewMenuProvider *menuProvider() const;

    //! Get currently selected layer. May be null
    QgsMapLayer *currentLayer() const;
    //! Set currently selected layer. Null pointer will deselect any layer.
    void setCurrentLayer( QgsMapLayer *layer );

    //! Get current node. May be null
    QgsLayerTreeNode *currentNode() const;
    //! Get current group node. If a layer is current node, the function will return parent group. May be null.
    QgsLayerTreeGroup *currentGroupNode() const;

    /** Get current legend node. May be null if current node is not a legend node.
     * @note added in QGIS 2.14
     */
    QgsLayerTreeModelLegendNode *currentLegendNode() const;

    //! Return list of selected nodes
    //! @arg skipInternal If true, will ignore nodes which have an ancestor in the selection
    QList<QgsLayerTreeNode*> selectedNodes( bool skipInternal = false ) const;
    //! Return list of selected nodes filtered to just layer nodes
    QList<QgsLayerTreeLayer*> selectedLayerNodes() const;

    //! Get list of selected layers
    QList<QgsMapLayer*> selectedLayers() const;

  public slots:
    //! Force refresh of layer symbology. Normally not needed as the changes of layer's renderer are monitored by the model
    void refreshLayerSymbology( const QString &layerId );

    //! Enhancement of QTreeView::expandAll() that also records expanded state in layer tree nodes
    //! @note added in QGIS 2.18
    void expandAllNodes();

    //! Enhancement of QTreeView::collapseAll() that also records expanded state in layer tree nodes
    //! @note added in QGIS 2.18
    void collapseAllNodes();

  signals:
    //! Emitted when a current layer is changed
    void currentLayerChanged( QgsMapLayer *layer );

  protected:
    void contextMenuEvent( QContextMenuEvent *event );

    void updateExpandedStateFromNode( QgsLayerTreeNode *node );

    QgsMapLayer *layerForIndex( const QModelIndex &index ) const;

  protected slots:

    void modelRowsInserted( const QModelIndex &index, int start, int end );
    void modelRowsRemoved();

    void updateExpandedStateToNode( const QModelIndex &index );

    void onCurrentChanged();
    void onExpandedChanged( QgsLayerTreeNode *node, bool expanded );
    void onModelReset();
};


/**
 * Implementation of this interface can be implemented to allow QgsLayerTreeView
 * instance to provide custom context menus (opened upon right-click).
 *
 * @see QgsLayerTreeView
 * @note added in 2.4
 */
class QgsLayerTreeViewMenuProvider
{
%TypeHeaderCode
#include <qgslayertreeview.h>
%End

  public:
    virtual ~QgsLayerTreeViewMenuProvider();

    //! Return a newly created menu instance (or null pointer on error)
    virtual QMenu *createContextMenu() = 0 /Factory/;
};