#include <iostream>
#include <ctime>
#include <random>
#include "timer.cpp"

// std::chrono::steady_clock?
std::mt19937_64 mt_rand(time(0));

class Board
{
    int * board;
    int width, height;
    int binMask;
    void reset(int);
public:
    Board(int, int);
    void display();
    void newRandomBoard(int);
    void newRandomBoard2(int);
    int getSquare(int, int);
    int totalCallsToRand;
};

Board::Board(int width, int height){
    // std::unique_pointer<int> ?
    std::cout << "In Board constructor" << std::endl;
    board = new int[height*width];
    for(int i=0; i<height*width; i++){
        board[i] = i%10;
    }
    binMask = 1;
    while(binMask < height*width) {
        binMask <<= 1;
        binMask++;
    }
    this->width = width;
    this->height = height;
    totalCallsToRand = 0;
}

void Board::display() {
    int i, j;

    std::cout << "+";
    for (i=0; i<width*2-1; i++){
        std::cout << "-";
    }
    std::cout << "+" << std::endl;
    for (i=0; i<height; i++){
        std::cout << "|";
        for (j=0; j<width; j++) {
            std::cout << getSquare(i, j);
            if (j < width-1){std::cout << " ";}
        }
        std::cout << "|" << std::endl;
    }
    std::cout << "+";
    for (i=0; i<width*2-1; i++){
        std::cout << "-";
    }
    std::cout << "+" << std::endl;
}

int Board::getSquare(int row, int column){
    if (0 <= row && 0 <= column){
        if (row < height && column < width) {
            return board[row*width + column];
        }
    }
    std::cout << "Warning. Out of bounds." << std::endl;
    return -1;
}

void Board::reset(int val){
    for (int i=0;i<width*height;i++){
        board[i] = val;
    }
}

void Board::newRandomBoard(int mines){
    int area = width*height;
    if(mines > area/2){
        std::cout << "Too many mines" << std::endl;
        return;
    }
    reset(0);
    for (int i=0;i<mines;i++) {
        int done = 0;
        while (done == 0){
            int xy = mt_rand() & binMask;
            totalCallsToRand++;
            if (xy < area && board[xy] == 0){
                done++;
                board[xy] = 1;
            }
        }
    }
}

void Board::newRandomBoard2(int mines) {
    int area = width*height;
    mines = (mines<0) ? 0 : ((mines>area) ? area : mines);
    int initialState = 0;
    int changedState = 1;
    if (mines > area/2) {
        initialState = 1;
        changedState = 0;
        mines = area - mines;
    }
    reset(initialState);
    int mask = 1;
    while(mask < area-mines){
        mask<<=1; mask++;
    }
    // Now we do the shuffle
    for (int i=area-mines; i<area; i++) {
        int gotRand = 0;
        int index;
        while(gotRand==0){
            index = mt_rand() & mask; // Take a power of 2 for good randomness
            totalCallsToRand++;
            if(index <= i){
                gotRand++;
            }
        }
        board[i] = board[index];
        board[index] = changedState;
        if (mask == i){
            mask<<=1; mask++;
        }
    }
}

void test(Board board) {
    for(int i=0;i<1000;i++){
        board.newRandomBoard2(99);
    }
    std::cout << "Total rand calls: " << board.totalCallsToRand << std::endl;
}

int main()
{
    Board board(30, 16);
    Timer timer;
    timer.start();
    test(board);
    double elapsed = timer.stop();
    std::cout << elapsed << std::endl;
    std::cout << "Total rand calls: " << board.totalCallsToRand << std::endl;
    return 0;
}