let drawing = 1;

const form = Array.from(document.forms.rules.elements);
const canvas = document.querySelector('#canvas');
const ctx = canvas.getContext('2d');
const main = document.querySelector('#main');
const dead = document.querySelector('#dead');
const live = document.querySelector('#live');
const startBtn = document.querySelector('#start');
const resetBtn = document.querySelector('#reset');
const cellSize = document.querySelector('#cellSize');
const loop = document.querySelector('#loop');

canvas.width = main.offsetWidth;
canvas.height = main.offsetHeight;

// TODO: Hide iterator inside
function evolve(state, acc, rules) {
  const [x, y, z, ...xs] = state;
  if (!xs.length) {
    return acc[acc.length - 1] + acc + acc[0];
  }

  const rule = x + y + z;
  const newAcc = acc.concat(rules[rule]);
  return evolve(y + z + xs.join(''), newAcc, rules);
}

function getRules() {
  const rules = {};

  form.reduce((_, i) => {
    if (i !== undefined
          && i.type === 'checkbox') {
      if (i.checked) rules[i.name] = '1';
      else rules[i.name] = '0';
    }
    return rules;
  }, rules);

  return rules;
}

function getDrawingValues(state, acc) {
  const cellDim = cellSize.value;

  return Object.keys(state).map(
    (key) => {
      const fillStyle = state[key] === '1' ? live.value : dead.value;
      return {
        move: [key * cellDim, acc * cellDim],
        fill: [key * cellDim, acc * cellDim, cellDim, cellDim],
        fillStyle,
      };
    },
  );
}

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

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

async function draw(state, acc) {
  if (drawing === 0) {
    return;
  }

  const position = acc * cellSize.value;
  if (position >= canvas.height && !loop.checked) return;

  const rules = getRules();
  const newState = evolve(state, '', rules);
  const line = getDrawingValues(newState, acc);

  line.map((cell) => {
    ctx.moveTo(...cell.move);
    ctx.fillRect(...cell.fill);
    ctx.fillStyle = cell.fillStyle;
    return cell;
  });

  await sleep(40);

  const newAcc = () => {
    if (position >= canvas.height && loop.checked) return 1;
    return acc;
  };

  await draw(newState, newAcc() + 1);
}

function reset() {
  drawing = 0;
  ctx.clearRect(0, 0, canvas.width, canvas.height);
}

startBtn.addEventListener('click', async () => {
  reset();

  await sleep(60);

  drawing = 1;

  const initialState = [...Array(canvas.width)].map(
    () => getRandomInt(0, 2).toString(),
  ).join('');

  draw(initialState, 1);
});

resetBtn.addEventListener('click', async () => {
  reset();
});