var cols, rows;
var w = 40;
var grid = [];
var current;
var stack = [];

function setup(){
    createCanvas(800, 800);
    cols = floor(width/w)
    rows = floor(height/w)
    //frameRate(6);

    for (var j = 0; j < rows; j++){
    	for (var i = 0; i < cols; i++){
    		var cell = new Cell(i,j);
    		grid.push(cell);
    	}
    }
    current = grid[0];
}

function draw(){
	background(150);
	for (var i = 0; i < grid.length; i++){
		grid[i].show();

	}
	current.visited = true;
	current.highlight();
	var next = current.checkNeighbors();
	if (next) {
		next.visited = true;
		stack.push(current);

		removeWalls(current, next);

		current = next;
	} else if (stack.length > 0){
		current = stack.pop();
	}

}


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(){
		var neighbors = [];
		
		var top = grid[index(i, j-1)];
		var right = grid[index(i+1, j)];
		var bottom = grid[index(i, j + 1)];
		var 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){
			var r = floor(random(0, neighbors.length));
			return neighbor[r];
		} else {
				return undefined;
			}
		this.highlight = function(){
				var x = this.i*w;
				var y  = this.j*w;
				noStroke();
				fill(0, 0, 255, 125);
				rect(x,y,w,w);
		}
		
	}

	this.show = function(){
		var x = this.i*w;
		var y  = this.j*w;
		stroke(255);
		if (this.walls[0]){
			line(x,y,x+w,y);
		}
		if (this.walls[1]){
			line(x+w,y,x+w,y+w);
		}
		if (this.walls[2]){
			line(x+w,y+w,x,y+w);
		}
		if (this.walls[3]){
			line(x,y+w,x,y);
		}
		if (this.visited){
			fill(255, 0, 255, 125);
			rect(x,y,w,w);
		}
	}
}

function removeWalls(a, b){
	var 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;
	}
	
	var 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;
	}

}