import { MutableRefObject } from 'react';

import { parsePadding } from '../utils';

export const getPositionHelpers = (
  containerRef: MutableRefObject<HTMLElement | undefined>,
  menuRef: MutableRefObject<HTMLElement>,
  menuScroll: Window | Element,
  boundingBoxPadding: string | undefined,
) => {
  const menuRect = menuRef.current.getBoundingClientRect();
  const thisWindow = containerRef.current?.ownerDocument.defaultView ?? window;
  const containerRect = (containerRef.current ?? thisWindow.document.body).getBoundingClientRect();

  const boundingRect =
    menuScroll === window || menuScroll === thisWindow
      ? {
          left: 0,
          top: 0,
          right: thisWindow.document.documentElement.clientWidth,
          bottom: thisWindow.innerHeight,
        }
      : (menuScroll as Element).getBoundingClientRect();
  const padding = parsePadding(boundingBoxPadding);

  // For left and top, overflows are negative value.
  // For right and bottom, overflows are positive value.
  const getLeftOverflow = (x: number) => x + containerRect.left - boundingRect.left - padding.left;
  const getRightOverflow = (x: number) => x + containerRect.left + menuRect.width - boundingRect.right + padding.right;
  const getTopOverflow = (y: number) => y + containerRect.top - boundingRect.top - padding.top;
  const getBottomOverflow = (y: number) =>
    y + containerRect.top + menuRect.height - boundingRect.bottom + padding.bottom;

  const confineHorizontally = (x: number) => {
    // If menu overflows to the left side, adjust x to have the menu contained within the viewport
    // and there is no need to check the right side;
    // if it doesn't overflow to the left, then check the right side
    let leftOverflow = getLeftOverflow(x);
    if (leftOverflow < 0) {
      x -= leftOverflow;
    } else {
      const rightOverflow = getRightOverflow(x);
      if (rightOverflow > 0) {
        x -= rightOverflow;
        // Check again to make sure menu doesn't overflow to the left
        // because it may go off-screen and cannot be scrolled into view.
        leftOverflow = getLeftOverflow(x);
        if (leftOverflow < 0) x -= leftOverflow;
      }
    }

    return x;
  };

  const confineVertically = (y: number) => {
    // Similar logic to confineHorizontally above
    let topOverflow = getTopOverflow(y);
    if (topOverflow < 0) {
      y -= topOverflow;
    } else {
      const bottomOverflow = getBottomOverflow(y);
      if (bottomOverflow > 0) {
        y -= bottomOverflow;
        // Check again to make sure menu doesn't overflow to the bottom
        // because it may go off screen and cannot be scroll into view.
        topOverflow = getTopOverflow(y);
        if (topOverflow < 0) y -= topOverflow;
      }
    }

    return y;
  };

  return {
    menuRect,
    containerRect,
    getLeftOverflow,
    getRightOverflow,
    getTopOverflow,
    getBottomOverflow,
    confineHorizontally,
    confineVertically,
  };
};