index.js

import postcss from 'postcss';
import getCustomSelectors from './lib/custom-selectors-from-root';
import transformRules from './lib/transform-rules';
import importCustomSelectorsFromSources from './lib/import-from';
import exportCustomSelectorsToDestinations from './lib/export-to';

export default postcss.plugin('postcss-custom-selectors', opts => {
	// whether to preserve custom selectors and rules using them
	const preserve = Boolean(Object(opts).preserve);

	// sources to import custom selectors from
	const importFrom = [].concat(Object(opts).importFrom || []);

	// destinations to export custom selectors to
	const exportTo = [].concat(Object(opts).exportTo || []);

	// promise any custom selectors are imported
	const customSelectorsPromise = importCustomSelectorsFromSources(importFrom);

	return async root => {
		const customProperties = Object.assign(
			await customSelectorsPromise,
			getCustomSelectors(root, { preserve })
		);

		await exportCustomSelectorsToDestinations(customProperties, exportTo);

		transformRules(root, customProperties, { preserve });
	};
});