// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

// * Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

// * Neither the name of Google Inc. nor the names of its contributors may be

//   used to endorse or promote products derived from this software without

//   specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

// POSSIBILITY OF SUCH DAMAGE.

//

// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_INTERNAL_GRAPH_H_

#define CERES_INTERNAL_GRAPH_H_

#include <limits>

#include <utility>

#include "ceres/integral_types.h"

#include "ceres/map_util.h"

#include "ceres/collections_port.h"

#include "ceres/internal/macros.h"

#include "ceres/types.h"

#include "glog/logging.h"

namespace ceres {

namespace internal {

// A unweighted undirected graph templated over the vertex ids. Vertex

// should be hashable.

template <typename Vertex>

class Graph {

 public:

  Graph() {}

  // Add a vertex.

  void AddVertex(const Vertex& vertex) {

    if (vertices_.insert(vertex).second) {

      edges_[vertex] = HashSet<Vertex>();

    }

  }

  bool RemoveVertex(const Vertex& vertex) {

    if (vertices_.find(vertex) == vertices_.end()) {

      return false;

    }

    vertices_.erase(vertex);

    const HashSet<Vertex>& sinks = edges_[vertex];

    for (typename HashSet<Vertex>::const_iterator it = sinks.begin();

         it != sinks.end(); ++it) {

      edges_[*it].erase(vertex);

    }

    edges_.erase(vertex);

    return true;

  }

  // Add an edge between the vertex1 and vertex2. Calling AddEdge on a

  // pair of vertices which do not exist in the graph yet will result

  // in undefined behavior.

  //

  // It is legal to call this method repeatedly for the same set of

  // vertices.

  void AddEdge(const Vertex& vertex1, const Vertex& vertex2) {

    DCHECK(vertices_.find(vertex1) != vertices_.end());

    DCHECK(vertices_.find(vertex2) != vertices_.end());

    if (edges_[vertex1].insert(vertex2).second) {

      edges_[vertex2].insert(vertex1);

    }

  }

  // Calling Neighbors on a vertex not in the graph will result in

  // undefined behaviour.

  const HashSet<Vertex>& Neighbors(const Vertex& vertex) const {

    return FindOrDie(edges_, vertex);

  }

  const HashSet<Vertex>& vertices() const {

    return vertices_;

  }

 private:

  HashSet<Vertex> vertices_;

  HashMap<Vertex, HashSet<Vertex> > edges_;

  CERES_DISALLOW_COPY_AND_ASSIGN(Graph);

};

// A weighted undirected graph templated over the vertex ids. Vertex

// should be hashable and comparable.

template <typename Vertex>

class WeightedGraph {

 public:

  WeightedGraph() {}

  // Add a weighted vertex. If the vertex already exists in the graph,

  // its weight is set to the new weight.

  void AddVertex(const Vertex& vertex, double weight) {

    if (vertices_.find(vertex) == vertices_.end()) {

      vertices_.insert(vertex);

      edges_[vertex] = HashSet<Vertex>();

    }

    vertex_weights_[vertex] = weight;

  }

  // Uses weight = 1.0. If vertex already exists, its weight is set to

  // 1.0.

  void AddVertex(const Vertex& vertex) {

    AddVertex(vertex, 1.0);

  }

  bool RemoveVertex(const Vertex& vertex) {

    if (vertices_.find(vertex) == vertices_.end()) {

      return false;

    }

    vertices_.erase(vertex);

    vertex_weights_.erase(vertex);

    const HashSet<Vertex>& sinks = edges_[vertex];

    for (typename HashSet<Vertex>::const_iterator it = sinks.begin();

         it != sinks.end(); ++it) {

      if (vertex < *it) {

        edge_weights_.erase(std::make_pair(vertex, *it));

      } else {

        edge_weights_.erase(std::make_pair(*it, vertex));

      }

      edges_[*it].erase(vertex);

    }

    edges_.erase(vertex);

    return true;

  }

  // Add a weighted edge between the vertex1 and vertex2. Calling

  // AddEdge on a pair of vertices which do not exist in the graph yet

  // will result in undefined behavior.

  //

  // It is legal to call this method repeatedly for the same set of

  // vertices.

  void AddEdge(const Vertex& vertex1, const Vertex& vertex2, double weight) {

    DCHECK(vertices_.find(vertex1) != vertices_.end());

    DCHECK(vertices_.find(vertex2) != vertices_.end());

    if (edges_[vertex1].insert(vertex2).second) {

      edges_[vertex2].insert(vertex1);

    }

    if (vertex1 < vertex2) {

      edge_weights_[std::make_pair(vertex1, vertex2)] = weight;

    } else {

      edge_weights_[std::make_pair(vertex2, vertex1)] = weight;

    }

  }

  // Uses weight = 1.0.

  void AddEdge(const Vertex& vertex1, const Vertex& vertex2) {

    AddEdge(vertex1, vertex2, 1.0);

  }

  // Calling VertexWeight on a vertex not in the graph will result in

  // undefined behavior.

  double VertexWeight(const Vertex& vertex) const {

    return FindOrDie(vertex_weights_, vertex);

  }

  // Calling EdgeWeight on a pair of vertices where either one of the

  // vertices is not present in the graph will result in undefined

  // behaviour. If there is no edge connecting vertex1 and vertex2,

  // the edge weight is zero.

  double EdgeWeight(const Vertex& vertex1, const Vertex& vertex2) const {

    if (vertex1 < vertex2) {

      return FindWithDefault(edge_weights_,

                             std::make_pair(vertex1, vertex2), 0.0);

    } else {

      return FindWithDefault(edge_weights_,

                             std::make_pair(vertex2, vertex1), 0.0);

    }

  }

  // Calling Neighbors on a vertex not in the graph will result in

  // undefined behaviour.

  const HashSet<Vertex>& Neighbors(const Vertex& vertex) const {

    return FindOrDie(edges_, vertex);

  }

  const HashSet<Vertex>& vertices() const {

    return vertices_;

  }

  static double InvalidWeight() {

    return std::numeric_limits<double>::quiet_NaN();

  }

 private:

  HashSet<Vertex> vertices_;

  HashMap<Vertex, double> vertex_weights_;

  HashMap<Vertex, HashSet<Vertex> > edges_;

  HashMap<std::pair<Vertex, Vertex>, double> edge_weights_;

  CERES_DISALLOW_COPY_AND_ASSIGN(WeightedGraph);

};

}  // namespace internal

}  // namespace ceres

#endif  // CERES_INTERNAL_GRAPH_H_