/****************************************************************************
 *   This file is part of the aGrUM/pyAgrum library.                        *
 *                                                                          *
 *   Copyright (c) 2005-2026 by                                             *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
 *                                                                          *
 *   The aGrUM/pyAgrum library is free software; you can redistribute it    *
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 *      the Free Software Foundation, either version 3 of the License,      *
 *      or (at your option) any later version,                              *
 *    - the MIT license (MIT),                                              *
 *    - or both in dual license, as here.                                   *
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 *   (see https://agrum.gitlab.io/articles/dual-licenses-lgplv3mit.html)    *
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 *   See LICENCES for more details.                                         *
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 *   SPDX-FileCopyrightText: Copyright 2005-2026                            *
 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
 *   SPDX-License-Identifier: LGPL-3.0-or-later OR MIT                      *
 *                                                                          *
 *   Contact  : info_at_agrum_dot_org                                       *
 *   homepage : http://agrum.gitlab.io                                      *
 *   gitlab   : https://gitlab.com/agrumery/agrum                           *
 *                                                                          *
 ****************************************************************************/


/**
 * @file
 * @brief C++20 concepts for aGrUM graph interfaces.
 *
 * Defines structural concepts capturing the public API of the four main
 * graph families: node-only, directed, undirected, and mixed.  These
 * concepts are used to constrain the template parameters of generic graph
 * algorithms (see algorithms/generic/).
 *
 * Dependency: graphElements.h (NodeId, NodeSet, Size).
 *
 * @author Pierre-Henri WUILLEMIN(_at_LIP6) and Christophe GONZALES(_at_AMU)
 */
#ifndef GUM_GRAPH_CONCEPTS_H
#define GUM_GRAPH_CONCEPTS_H

#include <concepts>

#include <agrum/base/graphs/graphElements.h>

namespace gum {

  /// @ingroup graph_group
  /// @{

  /**
   * @brief Concept for any graph that exposes node-level queries.
   *
   * Satisfied by every aGrUM graph class (DiGraph, UndiGraph, MixedGraph,
   * DAG, PDAG, …) since they all inherit from NodeGraphPart.
   */
  template < typename T >
  concept GUM_NodeGraphable = requires(const T g, NodeId id) {
    { g.existsNode(id) } -> std::convertible_to< bool >;
    { g.size() } -> std::convertible_to< Size >;
    { g.empty() } -> std::convertible_to< bool >;
  };

  /**
   * @brief Concept for directed graphs (arcs with parents/children).
   *
   * Satisfied by DiGraph, DAG, and the directed component of MixedGraph /
   * PDAG.  Refines GUM_NodeGraphable.
   */
  template < typename T >
  concept GUM_DiGraphable = GUM_NodeGraphable< T > && requires(const T g, NodeId u, NodeId v) {
    { g.existsArc(u, v) } -> std::convertible_to< bool >;
    { g.parents(u) } -> std::convertible_to< const NodeSet& >;
    { g.children(u) } -> std::convertible_to< const NodeSet& >;
  };

  /**
   * @brief Concept for undirected graphs (edges with neighbours).
   *
   * Satisfied by UndiGraph, CliqeGraph, and the undirected component of
   * MixedGraph / PDAG.  Refines GUM_NodeGraphable.
   */
  template < typename T >
  concept GUM_UndiGraphable = GUM_NodeGraphable< T > && requires(const T g, NodeId u, NodeId v) {
    { g.existsEdge(u, v) } -> std::convertible_to< bool >;
    { g.neighbours(u) } -> std::convertible_to< const NodeSet& >;
  };

  /**
   * @brief Concept for mixed graphs (both arcs and edges).
   *
   * Satisfied by MixedGraph and PDAG.  Refines both GUM_DiGraphable and
   * GUM_UndiGraphable.
   */
  template < typename T >
  concept GUM_MixedGraphable = GUM_DiGraphable< T > && GUM_UndiGraphable< T >;

  /// @}

}   // namespace gum

#endif   // GUM_GRAPH_CONCEPTS_H
