class Timer{
    bool timeUp, reset;
    public: 
	bool getTimeUp(){
        return timeUp;
    }
    bool setReset(){
        reset = true;
    }
    void start(int sec){
        reset = timeUp = false;
        time startTime = getCurrentTime();
        while(getCurrentTime() < startTime){
            if(reset == true){
                reset = false;
                return;
            }
        }
    }
};

enum Color{
    Black,
    White;
};

class User{
    int id;
    string email, name;
};

class Player : private User{
    int num;
    Color color;
    void setColor(){}
    void setNum(){}
};

class Piece{
    Color color;
    public: virtual unordered_set<string> getPossiblePositions(string currentPos) = 0;
};

class Queen : public Piece{
    virtual unordered_set<string> getPossiblePositions(string currentPos){
        //core logic
    }
};

class Board{
    int boardLength;
    unordered_map<string,Piece> positions; //map of position vs piece
    vector<Piece> killedPieces;
    Board(boardLength = 8)
    :boardLength(boardLength)
    {
        fill_map();
    }
    Color getColor(string pos){}
    
    unordered_set<string> getPossiblePositions(string pos, Color color){
        if(getColor(pos) != color)
            return {};
        return positions[pos].getPossiblePositions();
    }
    
    bool move(string src, string dest){
        //return true if all of the opponent's pieces are killed.
    }
};

class Chess{
    Player p1, p2, *currentPlayer, *winner;
    Board board;
    Timer timer;
    thread timerThread(timer.start(120)); // this starts a countdown.
    Chess(User p1, User p2, boardLength=8)
    :p1(p1)
    ,p2(p2)
    ,board(boardLength)
	{
        p1.setColor(White);
        p1.setNum(1);
        p2.setColor(Blacl);
        p2.setNum(2);
        currentPlayer = &p1;
        timerThread.start();
        thread checkTimeUpThread(checkTimeUp).start(); //works continuously throught out the game.
    }
    
    void checkTimeUp(){
        if(timer.getTimeUp()){
            if(currentPlayer == &p1)
                winner = &p2;
            else
                winner = &p1;
            terminate();
        }
    }
    
    unordered_set<string> getPossiblePositions(Player p, string pos){
        if(p != *currentPlayer)
            return {};
        return board.getPossiblePositions(pos,p.getColor());
    }
    
    bool move(Player, p, string src, string dest){
        mp = board.getPossiblePositions(src,p.getColor);
        if(validatePlayer(p) and mp.find(dest) != mp.end()){
            isWinner = board.move(src,dest);
            if(isWinner)
                terminate();
            timer.setReset(); //timerThread gets stopped now.
            change currentPlayer;
            timerThread.start(); //start timer again.
        }
        return false;
    }
};