let w;

let grid = [];

​

let current;

​

let stack = [];

​

function setup() {

  createCanvas(window.innerWidth, window.innerHeight);

  w = floor(width / 20)

  cols = floor(width / w);

  rows = floor(height / w);

  for (let j = 0; j < rows; j++) {

    for (let i = 0; i < cols; i++) {

      let cell = new Cell(i, j); 

      grid.push(cell);

    }

  }

  current = grid[0];

}

​

function draw() {

  background(51);

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

    grid[i].show();

  }

  // STEP 0 - Visit the current cell.

  current.visited = true;

​

  // STEP 1 - Randomly pick one of its neighbors, call it next.

  let next = current.checkNeighbors();

  if (next) {

    // STEP 2 - Push the current cell to the stack.

    stack.push(current);

    // STEP 3 - Remove their common wall (for both).

    removeWalls(current, next);

    // STEP 4 - Visit next, set current to next.

    next.visited = true;

    current = next

  } else if (stack.length > 0) {

    current = stack.pop();

  }

  for (let cell of stack) {

    cell.highlight(20, 220, 100, 80);

  }

  current.highlight(200, 140, 220, 120);

}

​

function index(i, j) {

  if (i < 0 || j < 0 || i > cols-1 || j > rows-1) {

    return -1; 

  }

  return i + j * cols;

}

​

function Cell(i, j) {

  this.i = i;

  this.j = j;

  this.walls = [true, true, true, true];

  this.visited = false;

  this.checkNeighbors = function() {

    let neighbors = [];

    let top     = grid[index(i, j-1)];

    let right   = grid[index(i+1, j)];

    let bottom  = grid[index(i, j+1)];

    let left    = grid[index(i-1, j)];

    if (top && !top.visited) {

      neighbors.push(top); 

    }

    if (right && !right.visited) {

      neighbors.push(right); 

    }

    if (bottom && !bottom.visited) {

      neighbors.push(bottom); 

    }

    if (left && !left.visited) {

      neighbors.push(left); 

    }

    if (neighbors.length > 0) {

      let r = floor(random(0, neighbors.length));

      return neighbors[r];

    } else {

      return undefined;

    }

    console.log(this.walls)

  }

  this.highlight = function(r, g, b, a) {

    let x = this.i * w;

    let y = this.j * w;

    noStroke();

    fill(r, g, b, a);

    rect(x, y, w, w);

  }

  this.show = function() {

    let x = this.i * w;

    let y = this.j * w;

    stroke(255);

    // TOP WALL

    if (this.walls[0]) {

      line(x    , y    , x + w, y);

    }

    // RIGHT WALL

    if (this.walls[1]) {

      line(x + w, y    , x + w, y + w);

    }

    // BOTTOM WALL

    if (this.walls[2]) {

      line(x + w, y + w, x    , y + w);

    }

    // LEFT WALL

    if (this.walls[3]) {

      line(x    , y + w, x    , y);

    }

    if (this.visited) {

      noStroke();

      fill(0, 255, 255, 80);

      rect(x, y, w, w);

    }

  }

}

​

function removeWalls(a, b) {

  let x = a.i - b.i;

  if (x === 1) {

    a.walls[3] = false;

    b.walls[1] = false;

  } else if (x === -1) {

    a.walls[1] = false;

    b.walls[3] = false;

  }

  let y = a.j - b.j;

  if (y === 1) {

    a.walls[0] = false;

    b.walls[2] = false;

  } else if (y === -1) {

    a.walls[2] = false;

    b.walls[0] = false;

  }

}

​