/**

 * 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.

 *

 * @flow

 */

import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';

import {getFiberCurrentPropsFromNode} from './legacy-events/EventPluginUtils';

export default function getListener(

  inst: Fiber,

  registrationName: string,

): Function | null {

  const stateNode = inst.stateNode;

  if (stateNode === null) {

    // Work in progress (ex: onload events in incremental mode).

    return null;

  }

  const props = getFiberCurrentPropsFromNode(stateNode);

  if (props === null) {

    // Work in progress.

    return null;

  }

  const listener = props[registrationName];

  if (listener && typeof listener !== 'function') {

    throw new Error(

      `Expected \`${registrationName}\` listener to be a function, instead got a value of \`${typeof listener}\` type.`,

    );

  }

  return listener;

}