/*
 * Copyright notice:
 *
 * Large parts of this file are heavily inspired if not downright copied from editor.js,
 * copyright MIT.
 * https://editorjs.io/
 */

import { isElement } from './dom';

export const getSelection = globalThis.getSelection ? globalThis.getSelection : () => null;

/**
 * Returns range from passed Selection object
 *
 * @param selection - Selection object to get Range from
 */
export const getRangeFromSelection = (selection: Selection): Range|null => {
  return selection && selection.rangeCount ? selection.getRangeAt(0) : null;
}


/**
 * Returns selected anchor element
 *
 * @returns {Element|null}
 */
export const getAnchorElementForSelection = (selection: Selection): Element | null => {
  const anchorNode = selection.anchorNode;

  if (!anchorNode) {
    return null;
  }

  if (!isElement(anchorNode)) {
    return anchorNode.parentElement;
  } else {
    return anchorNode;
  }
}

/**
 * Calculates position and size of selected text
 *
 * @returns {DOMRect}
 */
export const getRect = (selection: Selection): DOMRect => {
  const defaultRect = {
    x: 0,
    y: 0,
    width: 0,
    height: 0,
  } as DOMRect;

  if (selection.rangeCount === null || isNaN(selection.rangeCount)) {
    console.warn('Method SelectionUtils.rangeCount is not supported');
    return defaultRect;
  }

  if (selection.rangeCount === 0) {
    return defaultRect;
  }

  const range = selection.getRangeAt(0).cloneRange() as Range;

  let rect = { ...defaultRect };

  if (range.getBoundingClientRect) {
    rect = range.getBoundingClientRect() as DOMRect;
  }
  // Fall back to inserting a temporary element
  if (rect.x === 0 && rect.y === 0) {
    const span = document.createElement('span');

    if (span.getBoundingClientRect) {
      // Ensure span has dimensions and position by
      // adding a zero-width space character
      span.appendChild(document.createTextNode('\u200b'));
      range.insertNode(span);
      rect = span.getBoundingClientRect() as DOMRect;

      const spanParent = span.parentNode;
      if (spanParent) {
        spanParent.removeChild(span);

        // Glue any broken text nodes back together
        spanParent.normalize();
      }
    }
  }

  return rect;
};