/*
   Copyright (C) 2001-2006, William Joseph.
   All Rights Reserved.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined ( INCLUDED_ISCENEGRAPH_H )
#define INCLUDED_ISCENEGRAPH_H

#include <cstddef>
#include "generic/constant.h"
#include "signal/signalfwd.h"

template<typename value_type>
class Stack;
template<typename Contained>
class Reference;

namespace scene
{
class Instance;
const Instance* const nullInstancePointer = 0;
inline const Instance& nullInstance(){
	return *nullInstancePointer;
}

class Node;
const Node* const nullNodePointer = 0;
inline const Node& nullNode(){
	return *nullNodePointer;
}
}

typedef Reference<scene::Node> NodeReference;

typedef std::size_t TypeId;

const TypeId NODETYPEID_MAX = 64;
const TypeId NODETYPEID_NONE = NODETYPEID_MAX;

const TypeId INSTANCETYPEID_MAX = 64;
const TypeId INSTANCETYPEID_NONE = INSTANCETYPEID_MAX;

namespace scene
{
/// \brief A unique key to an instance of a node in the scene-graph.
typedef Stack<NodeReference> Path;

/// \brief A scene-graph - a Directed Acyclic Graph (DAG).
///
/// - Each node may refer to zero or more 'child' nodes (directed).
/// - A node may never have itself as one of its ancestors (acyclic).
/// - Each node may have more than one 'parent', thus having more than one 'instance' in the graph.
/// - Each instance is uniquely identified by the list of its ancestors plus itself, known as a 'path'.
class Graph
{
public:
virtual ~Graph() = default;
INTEGER_CONSTANT( Version, 1 );
STRING_CONSTANT( Name, "scenegraph" );

class Walker
{
public:
/// \brief Called before traversing the first child-instance of 'instance'. If the return value is false, the children of the current instance are not traversed.
virtual bool pre( const Path& path, Instance& instance ) const = 0;
/// \brief Called after traversing the last child-instance of 'instance'.
virtual void post( const Path& path, Instance& instance ) const {
}
};

/// \brief Returns the root-node of the graph.
virtual Node& root() = 0;
/// \brief Sets the root-node of the graph to be 'node'.
virtual void insert_root( Node& root ) = 0;
/// \brief Clears the root-node of the graph.
virtual void erase_root() = 0;
/// \brief Traverses all nodes in the graph depth-first, starting from the root node.
virtual void traverse( const Walker& walker ) = 0;
/// \brief Traverses all nodes in the graph depth-first, starting from 'start'.
virtual void traverse_subgraph( const Walker& walker, const Path& start ) = 0;
/// \brief Returns the instance at the location identified by 'path', or 0 if it does not exist.
virtual scene::Instance* find( const Path& path ) = 0;

/// \brief Invokes all scene-changed callbacks. Called when any part of the scene changes the way it will appear when the scene is rendered.
/// \todo Move to a separate class.
virtual void sceneChanged() = 0;
/// \brief Add a \p callback to be invoked when the scene changes.
/// \todo Move to a separate class.
virtual void addSceneChangedCallback( const SignalHandler& handler ) = 0;

/// \brief Invokes all bounds-changed callbacks. Called when the bounds of any instance in the scene change.
/// \todo Move to a separate class.
virtual void boundsChanged() = 0;
/// \brief Add a \p callback to be invoked when the bounds of any instance in the scene change.
virtual SignalHandlerId addBoundsChangedCallback( const SignalHandler& boundsChanged ) = 0;
/// \brief Remove a \p callback to be invoked when the bounds of any instance in the scene change.
virtual void removeBoundsChangedCallback( SignalHandlerId id ) = 0;

virtual TypeId getNodeTypeId( const char* name ) = 0;
virtual TypeId getInstanceTypeId( const char* name ) = 0;
};

class Traversable
{
public:
STRING_CONSTANT( Name, "scene::Traversable" );

class Observer
{
public:
/// \brief Called when a node is added to the container.
virtual void insert( Node& node ) = 0;
/// \brief Called when a node is removed from the container.
virtual void erase( Node& node ) = 0;
};

class Walker
{
public:
/// \brief Called before traversing the first child-node of 'node'. If the return value is false, the children of the current node are not traversed.
virtual bool pre( Node& node ) const = 0;
/// \brief Called after traversing the last child-node of 'node'.
virtual void post( Node& node ) const {
}
};
/// \brief Adds a node to the container.
virtual void insert( Node& node ) = 0;
/// \brief Removes a node from the container.
virtual void erase( Node& node ) = 0;
/// \brief Traverses the subgraphs rooted at each node in the container, depth-first.
virtual void traverse( const Walker& walker ) = 0;
/// \brief Returns true if the container contains no nodes.
virtual bool empty() const = 0;
};

class Instantiable
{
public:
STRING_CONSTANT( Name, "scene::Instantiable" );

class Observer
{
public:
/// \brief Called when an instance is added to the container.
virtual void insert( scene::Instance* instance ) = 0;
/// \brief Called when an instance is removed from the container.
virtual void erase( scene::Instance* instance ) = 0;
};

class Visitor
{
public:
virtual void visit( Instance& instance ) const = 0;
};

/// \brief Returns a new instance uniquely identified by 'path'.
virtual scene::Instance* create( const scene::Path& path, scene::Instance* parent ) = 0;
/// \brief Calls Visitor::visit(instance) for each instance in the container.
virtual void forEachInstance( const Visitor& visitor ) = 0;
/// \brief Adds an instance to the container.
virtual void insert( Observer* observer, const Path& path, scene::Instance* instance ) = 0;
/// \brief Returns an instance removed from the container.
virtual scene::Instance* erase( Observer* observer, const Path& path ) = 0;
};

class Cloneable
{
public:
STRING_CONSTANT( Name, "scene::Cloneable" );

/// \brief Returns a copy of itself.
virtual scene::Node& clone() const = 0;
};
}

#include "modulesystem.h"

template<typename Type>
class GlobalModule;
typedef GlobalModule<scene::Graph> GlobalSceneGraphModule;

template<typename Type>
class GlobalModuleRef;
typedef GlobalModuleRef<scene::Graph> GlobalSceneGraphModuleRef;

inline scene::Graph& GlobalSceneGraph(){
	return GlobalSceneGraphModule::getTable();
}

inline void AddSceneChangeCallback( const SignalHandler& handler ){
	GlobalSceneGraph().addSceneChangedCallback( handler );
}
inline void SceneChangeNotify(){
	GlobalSceneGraph().sceneChanged();
}



#endif