@react-navigation/core/src/useOptionsGetters.tsx

import type { ParamListBase } from '@react-navigation/routers';
import * as React from 'react';

import NavigationBuilderContext from './NavigationBuilderContext';
import NavigationStateContext from './NavigationStateContext';
import type { NavigationProp } from './types';

type Options = {
  key?: string;
  navigation?: NavigationProp<ParamListBase>;
  options?: object | undefined;
};

export default function useOptionsGetters({
  key,
  options,
  navigation,
}: Options) {
  const optionsRef = React.useRef<object | undefined>(options);
  const optionsGettersFromChildRef = React.useRef<
    Record<string, () => object | undefined | null>
  >({});

  const { onOptionsChange } = React.useContext(NavigationBuilderContext);
  const { addOptionsGetter: parentAddOptionsGetter } = React.useContext(
    NavigationStateContext
  );

  const optionsChangeListener = React.useCallback(() => {
    const isFocused = navigation?.isFocused() ?? true;
    const hasChildren = Object.keys(optionsGettersFromChildRef.current).length;

    if (isFocused && !hasChildren) {
      onOptionsChange(optionsRef.current ?? {});
    }
  }, [navigation, onOptionsChange]);

  React.useEffect(() => {
    optionsRef.current = options;
    optionsChangeListener();

    return navigation?.addListener('focus', optionsChangeListener);
  }, [navigation, options, optionsChangeListener]);

  const getOptionsFromListener = React.useCallback(() => {
    for (let key in optionsGettersFromChildRef.current) {
      if (optionsGettersFromChildRef.current.hasOwnProperty(key)) {
        const result = optionsGettersFromChildRef.current[key]?.();

        // null means unfocused route
        if (result !== null) {
          return result;
        }
      }
    }

    return null;
  }, []);

  const getCurrentOptions = React.useCallback(() => {
    const isFocused = navigation?.isFocused() ?? true;

    if (!isFocused) {
      return null;
    }

    const optionsFromListener = getOptionsFromListener();

    if (optionsFromListener !== null) {
      return optionsFromListener;
    }

    return optionsRef.current;
  }, [navigation, getOptionsFromListener]);

  React.useEffect(() => {
    return parentAddOptionsGetter?.(key!, getCurrentOptions);
  }, [getCurrentOptions, parentAddOptionsGetter, key]);

  const addOptionsGetter = React.useCallback(
    (key: string, getter: () => object | undefined | null) => {
      optionsGettersFromChildRef.current[key] = getter;
      optionsChangeListener();

      return () => {
        // eslint-disable-next-line @typescript-eslint/no-dynamic-delete
        delete optionsGettersFromChildRef.current[key];
        optionsChangeListener();
      };
    },
    [optionsChangeListener]
  );

  return {
    addOptionsGetter,
    getCurrentOptions,
  };
}