/* osgEarth
 * Copyright 2025 Pelican Mapping
 * MIT License
 */
#ifndef OSGEARTH_MAP_NODE_OBSERVER_H
#define OSGEARTH_MAP_NODE_OBSERVER_H 1

#include <osgEarth/Common>
#include <osgEarth/MapNode>

namespace osgEarth
{
    /**
     * This is a marker class for objects (and nodes) that reference a MapNode.
     *
     * The usage pattern for this class is to include it as a superclass using
     * multiple inheritance (if necessary) and to implement the set/get MapNode
     * methods. If you store a local reference to the MapNode, you should use
     * an osg::observer_ptr<> to do so!
     *
     * You can update as scene graph containing MapNodeObservers by using the
     * MapNodeObserverSetter visitor.
     */
    class /*header-only*/ MapNodeObserver
    {
    public:
        /**
         * Sets the map node's observer reference
         */
        virtual void setMapNode( MapNode* mapNode ) =0;

        /**
         * Gets the map node from its observer reference
         */
        virtual MapNode* getMapNode() =0;

        /**
         * dtor
         */
        virtual ~MapNodeObserver() { }
    };


    /**
     * Base class for a visitor that operates on MapNodeObserver instances
     * found in a scene graph.
     */
    class /*header-only*/ MapNodeObserverVisitor : public osg::NodeVisitor
    {
    public:
        using osg::NodeVisitor::apply;

        MapNodeObserverVisitor(osg::NodeVisitor::TraversalMode mode =osg::NodeVisitor::TRAVERSE_ALL_CHILDREN)
            : osg::NodeVisitor( mode ) { }
        
        virtual void apply( MapNodeObserver* m ) = 0;

        void tryApply( MapNodeObserver* m )
        {
            if ( m ) apply( m );
        }

        void apply( osg::Node& node )
        {
            tryApply( dynamic_cast<MapNodeObserver*>(&node) );
            tryApply( dynamic_cast<MapNodeObserver*>(node.getEventCallback()) );
            tryApply( dynamic_cast<MapNodeObserver*>(node.getUpdateCallback()) );
            tryApply( dynamic_cast<MapNodeObserver*>(node.getCullCallback()) );
            traverse( node );
        }
    };


    /**
     * Visitor that traverses a graph and calls setMapNode() on each
     * MapNodeObserver found.
     */
    class /*header-only*/ MapNodeReplacer : public MapNodeObserverVisitor
    {
    public:
        MapNodeReplacer( MapNode* mapNode ) : _mapNode(mapNode) { }

        void apply( MapNodeObserver* m )
        {
            m->setMapNode( _mapNode.get() );
        }

    private:
        osg::observer_ptr<MapNode> _mapNode;
    };

} // namespace osgEarth

#endif // OSGEARTH_MAP_NODE_OBSERVER_H
