@mui/base/utils/useCompoundItem.js

import * as React from 'react';
import { unstable_useEnhancedEffect as useEnhancedEffect } from '@mui/utils';
import { CompoundComponentContext } from './useCompound';

/**
 * Registers a child component with the parent component.
 *
 * @param id A unique key for the child component. If the `id` is `undefined`, the registration logic will not run (this can sometimes be the case during SSR).
 * @param itemMetadata Arbitrary metadata to pass to the parent component. This should be a stable reference (e.g. a memoized object), to avoid unnecessary re-registrations.
 * @param missingKeyGenerator A function that generates a unique id for the item.
 *   It is called with the set of the ids of all the items that have already been registered.
 *   Return `existingKeys.size` if you want to use the index of the new item as the id.
 *
 * @ignore - internal hook.
 */

export function useCompoundItem(id, itemMetadata) {
  const context = React.useContext(CompoundComponentContext);
  if (context === null) {
    throw new Error('useCompoundItem must be used within a useCompoundParent');
  }
  const {
    registerItem
  } = context;
  const [registeredId, setRegisteredId] = React.useState(typeof id === 'function' ? undefined : id);
  useEnhancedEffect(() => {
    const {
      id: returnedId,
      deregister
    } = registerItem(id, itemMetadata);
    setRegisteredId(returnedId);
    return deregister;
  }, [registerItem, itemMetadata, id]);
  return {
    id: registeredId,
    index: registeredId !== undefined ? context.getItemIndex(registeredId) : -1,
    totalItemCount: context.totalSubitemCount
  };
}