/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 */

import {useLexicalComposerContext} from '@lexical/react/LexicalComposerContext';
import {getActiveElement} from 'lexical';
import {useEffect} from 'react';

type Props = {
  defaultSelection?: 'rootStart' | 'rootEnd';
};

/**
 * Focuses the editor when the component is mounted. Pass `defaultSelection`
 * to control whether the selection is placed at the start (`'rootStart'`) or
 * end (`'rootEnd'`) of the root when there is no existing selection to restore.
 *
 * This is a legacy plugin. When building an editor with the extension API,
 * configure {@link AutoFocusExtension} instead.
 *
 * @returns `null`, this plugin renders no DOM of its own.
 */
export function AutoFocusPlugin({defaultSelection}: Props): null {
  const [editor] = useLexicalComposerContext();

  useEffect(() => {
    editor.focus(
      () => {
        // If we try and move selection to the same point with setBaseAndExtent, it won't
        // trigger a re-focus on the element. So in the case this occurs, we'll need to correct it.
        // Normally this is fine, Selection API !== Focus API, but fore the intents of the naming
        // of this plugin, which should preserve focus too.
        const rootElement = editor.getRootElement() as HTMLDivElement;
        // getActiveElement rather than document.activeElement, which reports
        // the shadow host when the editor is in a shadow root.
        const activeElement =
          rootElement !== null ? getActiveElement(rootElement) : null;
        if (
          rootElement !== null &&
          (activeElement === null || !rootElement.contains(activeElement))
        ) {
          // Note: preventScroll won't work in Webkit.
          rootElement.focus({preventScroll: true});
        }
      },
      {defaultSelection},
    );
  }, [defaultSelection, editor]);

  return null;
}