/** \file
 * \brief Declaration and implementation of GraphReduction class
 *        reduces by Leaves & Chains.
 *
 * \author Markus Chimani
 *
 * \par License:
 * This file is part of the Open Graph Drawing Framework (OGDF).
 *
 * \par
 * Copyright (C)<br>
 * See README.md in the OGDF root directory for details.
 *
 * \par
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * Version 2 or 3 as published by the Free Software Foundation;
 * see the file LICENSE.txt included in the packaging of this file
 * for details.
 *
 * \par
 * This program 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.
 *
 * \par
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, see
 * http://www.gnu.org/copyleft/gpl.html
 */

#pragma once

#include <ogdf/basic/Graph.h>
#include <ogdf/basic/List.h>
#include <ogdf/basic/basic.h>

namespace ogdf {


//! Creates a reduced graph by removing leaves, self-loops, and reducing chains.
/**
 * @ingroup graphs decomp
 *
 * GraphReduction is read-only !!!
 */
class OGDF_EXPORT GraphReduction : public Graph {
protected:
	const Graph* m_pGraph; // original graph
	NodeArray<node> m_vOrig; // corresponding node in original graph
	EdgeArray<List<edge>> m_eOrig; // corresponding edge in original graph

	NodeArray<node> m_vReduction; // corresponding node in graph copy
	EdgeArray<edge> m_eReduction; // corresponding chain of edges in graph copy

	GraphReduction() : m_pGraph(nullptr) { }

public:
	// construction
	explicit GraphReduction(const Graph& G);

	virtual ~GraphReduction() { }

	// returns original graph
	const Graph& original() const { return *m_pGraph; }

	// returns original node
	node original(node v) const { return m_vOrig[v]; }

	// returns original edges
	const List<edge>& original(edge e) const { return m_eOrig[e]; }

	// returns reduction of node v (0 if none)
	node reduction(node v) const { return m_vReduction[v]; }

	// returns reduction of edge e
	edge reduction(edge e) const { return m_eReduction[e]; }
};

}
