@mskcc/carbon-react/es/components/FeatureFlags/index.js

Carbon react components for the MSKCC DSM

/**
 * MSKCC 2021, 2024
 */

import { createScope, FeatureFlags as FeatureFlags$1 } from '@carbon/feature-flags';
import PropTypes from 'prop-types';
import React__default, { useContext, useState, useRef, useEffect, createContext } from 'react';

/**
 * Our FeatureFlagContext is used alongside the FeatureFlags component to enable
 * or disable feature flags in a given React tree
 */
const FeatureFlagContext = /*#__PURE__*/createContext(FeatureFlags$1);

/**
 * Supports an object of feature flag values with the `flags` prop, merging them
 * along with the current `FeatureFlagContext` to provide consumers to check if
 * a feature flag is enabled or disabled in a given React tree
 */
function FeatureFlags(_ref) {
  let {
    children,
    flags = {}
  } = _ref;
  const parentScope = useContext(FeatureFlagContext);
  const [prevParentScope, setPrevParentScope] = useState(parentScope);
  const [scope, updateScope] = useState(() => {
    const scope = createScope(flags);
    scope.mergeWithScope(parentScope);
    return scope;
  });
  if (parentScope !== prevParentScope) {
    const scope = createScope(flags);
    scope.mergeWithScope(parentScope);
    updateScope(scope);
    setPrevParentScope(parentScope);
  }

  // We use a custom hook to detect if any of the keys or their values change
  // for flags that are passed in. If they have changed, then we re-create the
  // FeatureFlagScope using the new flags
  useChangedValue(flags, isEqual, changedFlags => {
    const scope = createScope(changedFlags);
    scope.mergeWithScope(parentScope);
    updateScope(scope);
  });
  return /*#__PURE__*/React__default.createElement(FeatureFlagContext.Provider, {
    value: scope
  }, children);
}
FeatureFlags.propTypes = {
  children: PropTypes.node,
  /**
   * Provide the feature flags to enabled or disabled in the current React tree
   */
  flags: PropTypes.objectOf(PropTypes.bool)
};

/**
 * This hook will store previous versions of the given `value` and compare the
 * current value to the previous one using the `compare` function. If the
 * compare function returns true, then the given `callback` is invoked in an
 * effect.
 *
 * @param {any} value
 * @param {Function} compare
 * @param {Function} callback
 */
function useChangedValue(value, compare, callback) {
  const initialRender = useRef(false);
  const savedCallback = useRef(callback);
  const [prevValue, setPrevValue] = useState(value);
  if (!compare(prevValue, value)) {
    setPrevValue(value);
  }
  useEffect(() => {
    savedCallback.current = callback;
  });
  useEffect(() => {
    // We only want the callback triggered after the first render
    if (initialRender.current) {
      savedCallback.current(prevValue);
    }
  }, [prevValue]);
  useEffect(() => {
    initialRender.current = true;
  }, []);
}

/**
 * Access whether a given flag is enabled or disabled in a given
 * FeatureFlagContext
 *
 * @returns {boolean}
 */
function useFeatureFlag(flag) {
  const scope = useContext(FeatureFlagContext);
  return scope.enabled(flag);
}

/**
 * Access all feature flag information for the given FeatureFlagContext
 *
 * @returns {FeatureFlagScope}
 */
function useFeatureFlags() {
  return useContext(FeatureFlagContext);
}

/**
 * Compare two objects and determine if they are equal. This is a shallow
 * comparison since the objects we are comparing are objects with boolean flags
 * from the flags prop in the `FeatureFlags` component
 *
 * @param {object} a
 * @param {object} b
 * @returns {boolean}
 */
function isEqual(a, b) {
  if (a === b) {
    return true;
  }
  for (const key of Object.keys(a)) {
    if (a[key] !== b[key]) {
      return false;
    }
  }
  for (const key of Object.keys(b)) {
    if (b[key] !== a[key]) {
      return false;
    }
  }
  return true;
}

export { FeatureFlagContext, FeatureFlags, useFeatureFlag, useFeatureFlags };