#ifndef TARJAN_H_
#define TARJAN_H_

#include "graph/graph.h"
using namespace graph;

#include <stack>
#include <iostream>
#include <ranges>
#include <iterator>
#include <algorithm>

namespace algorithm {

template<typename T>
class Tarjan {
public:
  Tarjan(Graph<T> G) : G(G) {}

  void findSCC();

  void strongConnect(Vertex<T>& v);

  std::uint16_t index = 0;
  std::stack<Vertex<T>> S;
private:
  Graph<T> G;
};

template<typename T>
void Tarjan<T>::strongConnect(Vertex<T>& v) {
  v.index, v.lowlink = index++;
  v.onStack = true;
  S.push(v);

  for (auto& w : v.edges) {
    if (w.index == -1) {
      // successor w has not yet been visited, recurse on it
      strongConnect(w);
      v.lowlink = std::min(v.lowlink, w.lowlink);
    } else if (w.onStack) {
      // successor w is in stack S and hence in the current SCC
      // if w is not on stack, then (v, w) is an edge pointing to an SCC
      // already found and must be ignored
      v.lowlink = std::min(v.lowlink, w.index);
    }
  }

  // if v is a root node, pop the stack and generate an SCC
  if (v.lowlink = v.index) {
    // start a new SCC
    Vertex<T> w;
    do {
      w = S.top();
      S.pop();
      // add w to current SCC

    } while (w != v);
  }
}

template<typename T>
void Tarjan<T>::findSCC() {

  for (auto& vertex : G.vertices) {
    if (vertex.index == -1) {
      strongConnect(vertex);
    }
  }
}

} // namespace algorithm

#endif