#include <iostream>
#include <string>
#include <stack>

class GameState
{
public:
  virtual ~GameState() = default;

  virtual void print() const = 0;
                                     
  virtual GameState* handle(std::string const& input) = 0;
};

class GuessTheWord : public GameState
{
public:
  GuessTheWord(std::string const& answer) : GameState{}, answer{answer}, n{3} {}

  void print() const
  {
    std::cout << "Guess the word, attempt " << n << ": " << std::endl;
  }
                                     
  GameState* handle(std::string const& input)
  {
    if (input == answer)
    {
      std::cout << "Great input, you win!" << std::endl;
      return nullptr;
    }

    if (--n <= 0)
    {
      std::cout << "End of attempts, you loose!" << std::endl;
      return nullptr;
    }

    std::cout << "Keep trying!" << std::endl;
    return this;
  }
  
private:
  std::string answer;
  int n;
};

class Menu : public GameState
{
public:
  Menu(std::string const& name) : GameState{}, name{name} {}
  
  void print() const
  {
    std::cout << "Welcome to " << name << ", please select:\n"
              << "1 Play\n"
              << "2 Quit\n"
              << std::endl;
  }
  
  GameState* handle(std::string const& input)
  {
    if (input == "1")
      return new GuessTheWord{"Klas"};
    else if (input == "2")
      return nullptr;
    else
      std::cerr << "Bad input, Please enter 1 or 2." << std::endl;
    
    return this;
  }

private:
  std::string name;
};

int main()
{
  // Keep the current state at the top of a stack
  std::stack<GameState*> state_stack;
  
  // A menu should be active when we enter the game
  state_stack.push(new Menu{"The Game"});

  // Keep runnig the game until all states are completed
  while ( ! state_stack.empty() )
  {
    // Fetch the current active state
    GameState* active_state = state_stack.top();

    // Let the active state instruct the user
    active_state->print();
    
    std::string input{};
    std::cin >> input;
    
    // Let the active state handle user input
    GameState* next{ active_state->handle(input) };

    if (next == nullptr)
    {
      // If handle returns nullptr the active_state is completed and should cease it's existance, pop it
      delete active_state;
      state_stack.pop();
    }
    else if (next != active_state)
    {
      // If handle returns a new state wh should complete that before this one, push it to the stack
      state_stack.push(next);
    }
    else if (next == active_state)
    {
      // If handle returns pointer to its own state object, keep running that state, do nothing
    }
  }
  return 0;
}