// TODO: Hide accumulator 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 conwayRules(cell, neighbors) {
  // loneliness rule
  if (cell === 1 && neighbors < 2) return 0;
  // overpopulation rule
  if (cell === 1 && neighbors > 3) return 0;
  // born when three live neighbors rule
  if (cell === 0 && neighbors === 3) return 1;
  // the cell remains the same if none apply
  return cell;
}

function getDrawingValues(state, acc, cell) {
  const d = cell.dimension;
  return Object.keys(state).map(
    (key) => {
      const fillStyle = state[key] === '1' ? cell.liveColor : cell.deadColor;
      return {
        move: [key * d, acc * d],
        fill: [key * d, acc * d, d, d],
        fillStyle,
      };
    },
  );
}

function initialState1D(width, initFn, args) {
  return [...Array(width)].map(
    () => initFn(...args).toString(),
  ).join('');
}

function initialState2D(width, height, initFn, args) {
  return [...Array(height)].map(
    () => [...Array(width)].map(() => initFn(...args)),
  );
}

export {
  evolve, getDrawingValues, initialState1D, initialState2D,
};