#include <SFML/Graphics.hpp>
#include <iostream>

using namespace sf;

int main()
{
  // app window
  RenderWindow app(VideoMode(256,256), "15-Puzzle!");
  app.setFramerateLimit(60);

  Texture t;
  t.loadFromFile("/Users/alleyuan/code-snippets/16_games/06 15-Puzzle/images/15.png");

  int w = 64; // width of square in texture
  int grid[6][6] = {0}; // grid
  Sprite sprite[20]; // blocks

  // set grid (position -> number) and sprites (number -> sprite)
  int n = 0;
  for (int i = 0; i < 4; i++)
    for (int j = 0; j < 4; j++)
    {
      n++;
      sprite[n].setTexture(t);
      sprite[n].setTextureRect(IntRect(i*w,j*w,w,w));
      grid[i+1][j+1] = n;
    }

  // game loop
  while (app.isOpen())
  {
    Event e;
    // event handlers
    while (app.pollEvent(e))
    {
      if (e.type == Event::Closed)
        app.close();

      if (e.type == Event::MouseButtonPressed)
        // left click handler
        if (e.key.code == Mouse::Left)
        {
          // grab mouse coordinates
          Vector2i pos = Mouse::getPosition(app);
          int x = pos.x/w + 1;
          int y = pos.y/w + 1;

          int dx = 0;
          int dy = 0;

          // find the offset of (x,y) from the blank square
          if (grid[x+1][y] == 16) { dx = 1; dy = 0; };
          if (grid[x][y+1] == 16) { dx = 0; dy = 1; };
          if (grid[x][y-1] == 16) { dx = 0; dy = -1; };
          if (grid[x-1][y] == 16) { dx = -1; dy = 0; };

          // swap (x,y) with the blank square if they're adjacent along the coordinate axes
          int n = grid[x][y];
          grid[x][y] = 16;
          grid[x+dx][y+dy] = n;
        }
    }

    app.clear(Color::White);
    for (int i = 0; i < 4; i++)
      for (int j = 0; j < 4; j++)
      {
        int n = grid[i+1][j+1];
        sprite[n].setPosition(i*w,j*w);
        app.draw(sprite[n]);
      }

    app.display();
  }
}