BetterSEQTA-Plus/src/interface/utils/portal.ts

import type { Action } from "svelte/action";

/**
 * Svelte action that moves the element to a different DOM target.
 * Defaults to the nearest ShadowRoot so styles remain intact when the app
 * is rendered inside a shadow DOM. Falls back to document.body otherwise.
 * Keeps all Svelte reactivity/events intact while escaping ancestor stacking contexts.
 */
export const portal: Action<HTMLElement, HTMLElement | ShadowRoot | undefined> = (node, target) => {
  const root = node.getRootNode();
  const dest = target ?? (root instanceof ShadowRoot ? root : document.body);
  dest.appendChild(node);

  return {
    update(newTarget) {
      (newTarget ?? dest).appendChild(node);
    },
    destroy() {
      node.remove();
    },
  };
};