const height = 512;
const width = 512;
const gridWidth = 64;
const gridHeight = 64;
const tileWidth = width/gridWidth;
const tileHeight = height/gridHeight;
let colorMap = 
   [[0,0,0],
    [0,0,255],
    [0,255,0],
    [255,0,0],
    [0,255,255],
    [255,0,255],
    [255,255,0],
    [255,255,255]];
let sandpiles = Array(gridHeight);
let oldpiles = new Array(sandpiles.length);
    

function setup() {
    createCanvas(width, height);
    
    for(let i = 0; i < gridHeight; i++){
        sandpiles[i] = Array(gridWidth);
        for(let j = 0; j < gridWidth; j++)
            sandpiles[i][j] = 0;
    }
    sandpiles[gridHeight/2][gridWidth/2] = 10000; 
    //sandpiles[gridHeight/2][gridWidth/2+1] = 4;
    
    for(let i = 0; i < gridHeight; i++)
        oldpiles[i] = new Array(sandpiles[i].legnth);

   // for(let k = 0; k< 10000; k++)
   //     update_sandpiles_in();
    
    noStroke();   
    frameRate(5);
}

function update_sandpiles() {
    for(let i = 0; i < gridHeight; i++)
        for(let j = 0; j < gridWidth; j++)
            oldpiles[i][j] = sandpiles[i][j];
    
    for(let i = 0; i < gridHeight; i++)
        for(let j = 0; j < gridWidth; j++){
            if (oldpiles[i][j] > 4){
                sandpiles[i][j] -= 4;
                if(i > 0)
                    sandpiles[i-1][j]++;
                if(j > 0)
                    sandpiles[i][j-1]++;
                if(i < gridHeight-1)
                    sandpiles[i+1][j]++;
                if(j < gridWidth-1)
                    sandpiles[i][j+1]++;
            }
        }

}

function update_sandpiles_in() {
    for(let k = 0; k < 2; k++)
    for(let i = 0; i < gridHeight; i++){
        for(let j = (i+k)%2; j < gridWidth; j+= 2){
            //sandpiles[i][j] = 3+k;
            if (sandpiles[i][j] > 4){
                sandpiles[i][j] -= 4;
                if(i > 0)
                    sandpiles[i-1][j]++;
                if(j > 0)
                    sandpiles[i][j-1]++;
                if(i < gridHeight-1)
                    sandpiles[i+1][j]++;
                if(j < gridWidth-1)
                    sandpiles[i][j+1]++;
            }
        }
    }
}

function draw() {
    update_sandpiles_in();
    // put drawing code her
    background(0);
    for(let i = 0; i < gridHeight; i++)
        for(let j = 0; j < gridWidth; j++){
            let color = colorMap[constrain(sandpiles[i][j],0,7)];
            fill(color[0],color[1], color[2]);
            rect( j*tileWidth, i*tileHeight,tileWidth,tileWidth);        
    }
    //noLoop();
}