utils.ts

export type GapMode = 'padding' | 'margin';

export interface GapOffset {
  left: number;
  top: number;
  right: number;
  gap: number;
}

export const zeroGap = {
  left: 0,
  top: 0,
  right: 0,
  gap: 0,
};

const parse = (x: string | null) => parseInt(x || '', 10) || 0;

const getOffset = (gapMode: GapMode): number[] => {
  const cs = window.getComputedStyle(document.body);

  if (process.env.NODE_ENV !== 'production') {
    if (cs.overflowY === 'hidden') {
      console.error(
        'react-remove-scroll-bar: cannot calculate scrollbar size because it is removed (overflow:hidden on body'
      );
    }
  }

  const left = cs[gapMode === 'padding' ? 'paddingLeft' : 'marginLeft'];
  const top = cs[gapMode === 'padding' ? 'paddingTop' : 'marginTop'];
  const right = cs[gapMode === 'padding' ? 'paddingRight' : 'marginRight'];

  return [parse(left), parse(top), parse(right)];
};

export const getGapWidth = (gapMode: GapMode = 'margin'): GapOffset => {
  if (typeof window === 'undefined') {
    return zeroGap;
  }

  const offsets = getOffset(gapMode);
  const documentWidth = document.documentElement.clientWidth;
  const windowWidth = window.innerWidth;

  return {
    left: offsets[0],
    top: offsets[1],
    right: offsets[2],
    gap: Math.max(0, windowWidth - documentWidth + offsets[2] - offsets[0]),
  };
};