// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/CodingChallenges/165-slide-puzzle.html

// https://youtu.be/uQZLzhrzEs4

​

// Image: https://editor.p5js.org/codingtrain/sketches/o_ljlLilZ

// Video: https://editor.p5js.org/codingtrain/sketches/YnLX7bGwW

// Canvas: https://editor.p5js.org/codingtrain/sketches/MVCd9trLw

​

​

// Source image to chop up

let source;

​

// Tiles configuration

let tiles = [];

let cols = 4;

let rows = 4;

let w, h;

​

// Order of tiles

let board = [];

​

// Loading the image

function preload() {

  source = loadImage("choochoobot.png");

}

​

function setup() {

  createCanvas(400, 400);

  // pixel dimensions of each tiles

  w = width / cols;

  h = height / rows;

  // Chop up source image into tiles

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      let x = i * w;

      let y = j * h;

      let img = createImage(w, h);

      img.copy(source, x, y, w, h, 0, 0, w, h);

      let index = i + j * cols;

      board.push(index);

      let tile = new Tile(index, img);

      tiles.push(tile);

    }

  }

  // Remove the last tile

  tiles.pop();

  board.pop();

  // -1 means empty spot

  board.push(-1);

  // Shuffle the board

  simpleShuffle(board);

}

​

// Swap two elements of an array

function swap(i, j, arr) {

  let temp = arr[i];

  arr[i] = arr[j];

  arr[j] = temp;

}

​

// Pick a random spot to attempt a move

// This should be improved to select from only valid moves

function randomMove(arr) {

  let r1 = floor(random(cols));

  let r2 = floor(random(rows));

  move(r1, r2, arr);

}

​

// Shuffle the board

function simpleShuffle(arr) {

  for (let i = 0; i < 100000; i++) {

    randomMove(arr);

  }

}

​

// Move based on click

function mousePressed() {

  let i = floor(mouseX / w);

  let j = floor(mouseY / h);

  move(i,j,board);

}

​

​

​

function draw() {

  background(0);

​

  // Draw the current board

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      let index = i + j * cols;

      let x = i * w;

      let y = j * h;

      let tileIndex = board[index];

      if (tileIndex > -1) {

        let img = tiles[tileIndex].img;

        image(img, x, y, w, h);

      }

    }

  }

  // Show it as grid

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      let x = i * w;

      let y = j * h;

      strokeWeight(2);

      noFill();

      rect(x, y, w, h);

    }

  }

  // If it is solved

  if (isSolved()) {

    console.log("SOLVED");

  }

}

​

// Check if solved

function isSolved() {

  for (let i = 0; i < board.length-1; i++) {

    if (board[i] !== tiles[i].index) {

      return false;

    }

  }

  return true;

}

​

// Swap two pieces

function move(i, j, arr) {

  let blank = findBlank();

  let blankCol = blank % cols;

  let blankRow = floor(blank / rows);

  // Double check valid move

  if (isNeighbor(i, j, blankCol, blankRow)) {

    swap(blank, i + j * cols, arr);

  }

}

​

// Check if neighbor

function isNeighbor(i, j, x, y) {

  if (i !== x && j !== y) {

    return false;

  }

​

  if (abs(i - x) == 1 || abs(j - y) == 1) {

    return true;

  }

  return false;

}

​

​

// Probably could just use a variable

// to track blank spot

function findBlank() {

  for (let i = 0; i < board.length; i++) {

    if (board[i] == -1) return i;

  }

}

​