/**
 * External dependencies
 */
import { CacheProvider } from '@emotion/react';
import createCache from '@emotion/cache';
import * as uuid from 'uuid';

/**
 * Internal dependencies
 */
import type { StyleProviderProps } from './types';

const uuidCache = new Set();
// Use a weak map so that when the container is detached it's automatically
// dereferenced to avoid memory leak.
const containerCacheMap = new WeakMap();

const memoizedCreateCacheWithContainer = ( container: HTMLElement ) => {
	if ( containerCacheMap.has( container ) ) {
		return containerCacheMap.get( container );
	}

	// Emotion only accepts alphabetical and hyphenated keys so we just
	// strip the numbers from the UUID. It _should_ be fine.
	let key = uuid.v4().replace( /[0-9]/g, '' );
	while ( uuidCache.has( key ) ) {
		key = uuid.v4().replace( /[0-9]/g, '' );
	}
	uuidCache.add( key );

	const cache = createCache( { container, key } );
	containerCacheMap.set( container, cache );
	return cache;
};

export function StyleProvider( props: StyleProviderProps ) {
	const { children, document } = props;

	if ( ! document ) {
		return null;
	}

	const cache = memoizedCreateCacheWithContainer( document.head );

	return <CacheProvider value={ cache }>{ children }</CacheProvider>;
}

export default StyleProvider;