'use strict';

const rules = {
  "111": "0",
  "110": "1",
  "101": "0",
  "100": "1",
  "011": "0",
  "010": "0",
  "001": "0",
  "000": "1"
}

function getRandomInt(min, max) {
  min = Math.ceil(min);
  max = Math.floor(max);
  // The maximum is exclusive and the minimum is inclusive
  return Math.floor(Math.random() * (max - min) + min); 
}

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

function evolve(state, acc) {
  const [x, y, z, ...xs] = state;

  if (!xs.length) {
    return acc + x + acc[0] + acc[1]
  }
  else {
    const rule = x + y + z;
    const new_acc = acc.concat(rules[rule]);
    return evolve(y + z + xs.join(""), new_acc)
  }
}

function draw(state, context, acc) {
  const cell_dim = 2

  Object.keys(state).forEach(
    function (key) {
      if(state[key] == "1") {
        context.fillStyle="black";
        context.moveTo(key * cell_dim, acc * cell_dim)
        context.fillRect(key * cell_dim, acc * cell_dim, cell_dim, cell_dim)
      }
    })
}

window.addEventListener("load", async function() {
  const canvas = document.getElementById("canvas")
  canvas.width = window.innerWidth
  canvas.height = window.innerHeight
  const ctx = canvas.getContext("2d")

  const initial_state = [...Array(canvas.width)].map(
    _=> getRandomInt(0, 2).toString()
  ).join("")

  var new_state = evolve(initial_state, "")
  var acc = 0
  
  while(acc < canvas.width) {
    draw(new_state, ctx, acc)
    new_state = evolve(new_state, "")
    acc++
    await sleep(100)
  }
})