#ifndef BREADTH_FIRST_SEARCH_H_
#define BREADTH_FIRST_SEARCH_H_

#include "graph/digraph.h"

#include <queue>

using namespace graph;

namespace algo {

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

  BreadthFirstSearch(Digraph<T> G) : G(G) {}

  std::map<T, std::set<T>> execute(const T& root);

  // Initialize LU table that show which vertices have been traversed 
  std::map<T, bool> initExplore();
private:
  Graph<T> G;
}; 

template<typename T>
std::map<T, bool> BreadthFirstSearch<T>::initExplore() {
  std::map<T, bool> graphExplore;
  for (const auto& v : G.adjMatrix) {
    graphExplore[v.first] = false;
  }
  return graphExplore;
}

template<typename T>
std::map<T, std::set<T>> BreadthFirstSearch<T>::execute(const T& root) {
  std::map<T, std::set<T>> tree;
  std::map<T, bool> graphExplore = initExplore();
  std::queue<T> Q;
  Q.push(root);
  graphExplore[root] = true;

  while (!Q.empty()) {
    const auto v = Q.front();
    Q.pop();

    for (const auto& u : G.adjMatrix[v]) {
      if (!graphExplore[u]) {
        graphExplore[u] = true;
        tree[v].insert(u);
        Q.push(u);
      }
    }
  }

  return tree;
}

} // namespace algo

#endif