#ifndef GRAPH_H_
#define GRAPH_H_

#include <map>
#include <set>
#include <utility>
#include <vector>
#include <iostream>

namespace graph {

template<typename T>
class Graph {
public:
  Graph() = default;

  // Add vertex v
  void insert(const T& v);

  // Add edge between v and u
  void insert(const T& v, const T& u);

  // Reverse graph directions
  Graph<T> reverse();

  // Number of vertices
  std::uint16_t V();

  // Number of edges
  // TODO: Calculate bidirectional edges once
  std::uint16_t E();

  // Adjacency matrix representation
  std::set<T> vertices;
  std::map<T, std::set<T>> adjMatrix;
};

template<typename T>
void Graph<T>::insert(const T& v) {
  vertices.insert(v);
}

template<typename T>
void Graph<T>::insert(const T& v, const T& u) {
  vertices.insert(v);
  vertices.insert(u);
  adjMatrix[v].insert(u);
}

template<typename T>
Graph<T> Graph<T>::reverse() {
  return Graph<T>();
}

template<typename T>
std::uint16_t Graph<T>::V() {
  return vertices.size();
}

template<typename T>
std::uint16_t Graph<T>::E() {
  std::uint16_t edges = 0;
  for (const auto& v : vertices) {
    edges += adjMatrix[v].size();
  }
  return edges;
}

} // namespace graph

#endif