let scrollBarWidth;

export const getScrollBarWidth = () => {
  if (scrollBarWidth !== undefined) return scrollBarWidth;

  const outer = document.createElement('div');
  outer.style.visibility = 'hidden';
  outer.style.width = '100px';
  outer.style.position = 'absolute';
  outer.style.top = '-9999px';
  document.body.appendChild(outer);

  const widthNoScroll = outer.offsetWidth;
  outer.style.overflow = 'scroll';

  const inner = document.createElement('div');
  inner.style.width = '100%';
  outer.appendChild(inner);

  const widthWithScroll = inner.offsetWidth;
  outer.parentNode.removeChild(outer);

  return widthNoScroll - widthWithScroll;
};

export const getCell = function(event) {
  let cell = event.target;

  while (cell && cell.tagName.toUpperCase() !== 'HTML') {
    if (cell.tagName.toUpperCase() === 'TD') {
      return cell;
    }
    cell = cell.parentNode;
  }

  return null;
};

export const getValueByPath = function(object, prop) {
  prop = prop || '';
  const paths = prop.split('.');
  let current = object;
  let result = null;
  for (let i = 0, j = paths.length; i < j; i++) {
    const path = paths[i];
    if (!current) break;

    if (i === j - 1) {
      result = current[path];
      break;
    }
    current = current[path];
  }
  return result;
};

const isObject = function(obj) {
  return obj !== null && typeof obj === 'object';
};

export const orderBy = function(array, sortKey, reverse) {
  if (!sortKey) {
    return array;
  }
  const order = (reverse && reverse < 0) ? -1 : 1;

  // sort on a copy to avoid mutating original array
  return array.slice().sort(function(a, b) {
    if (sortKey !== '$key') {
      if (isObject(a) && '$value' in a) a = a.$value;
      if (isObject(b) && '$value' in b) b = b.$value;
    }
    a = isObject(a) ? getValueByPath(a, sortKey) : a;
    b = isObject(b) ? getValueByPath(b, sortKey) : b;
    return a === b ? 0 : a > b ? order : -order;
  });
};