index.js

const { forEachOfLimit } = require('async');
const rtlcss = require('rtlcss');
const cssDiff = require('@romainberger/css-diff');
const cssnano = require('cssnano');
const { ConcatSource } = require('webpack-sources');
const path = require('path');

class RTLCSSPlugin {
	constructor(options) {
		this.options = {
			filename: false,
			options: {},
			plugins: [],
			...options
		}
	}

	apply(compiler) {
		compiler.hooks.emit.tapAsync('RTLCSSPlugin', (compilation, callback) => {
			forEachOfLimit(compilation.chunks, 5, (chunk, key, cb) => {
				const rtlFiles = [];
				let cssnanoPromise = Promise.resolve();

				chunk.files.forEach(asset => {
					const match = this.options.test ? new RegExp(this.options.test).test(asset) : true;

					if (path.extname(asset) !== '.css') {
						return;
					}

					const baseSource = compilation.assets[asset].source();
					let filename = '';
					let rtlSource = '';

					if (match) {
						rtlSource = rtlcss.process(baseSource, this.options.options, this.options.plugins);

						if (this.options.filename instanceof Array && this.options.filename.length === 2) {
							filename = asset.replace(this.options.filename[0], this.options.filename[1]);
						} else if (this.options.filename) {
							filename = this.options.filename;

							if (/\[contenthash]/.test(this.options.filename)) {
								const hash = createHash('md5').update(rtlSource).digest('hex').substr(0, 10);
								filename = filename.replace('[contenthash]', hash);
							}
							if (/\[id]/.test(this.options.filename)) {
								filename = filename.replace('[id]', chunk.id);
							}
							if (/\[name]/.test(this.options.filename)) {
								filename = path.dirname(asset) + '/' + filename.replace('[name]', path.basename(asset, '.css'));
							}
							if (/\[file]/.test(this.options.filename)) {
								filename = filename.replace('[file]', asset);
							}
							if (/\[filebase]/.test(this.options.filename)) {
								filename = filename.replace('[filebase]', path.basename(asset));
							}
							if (/\[ext]/.test(this.options.filename)) {
								filename = filename.replace('.[ext]', path.extname(asset));
							}
						} else {
							const newFilename = `${path.basename(asset, '.css')}.rtl`;
							filename = asset.replace(path.basename(asset, '.css'), newFilename);
						}

						if (this.options.diffOnly) {
							rtlSource = cssDiff(baseSource, rtlSource)
						}
					}

					if (this.options.minify !== false) {
						let nanoOptions = { from: undefined }
						if (typeof this.options.minify === 'object') {
							nanoOptions = this.options.minify;
						}

						cssnanoPromise = cssnanoPromise.then(() => {
							let minify = cssnano.process( baseSource, nanoOptions).then(output => {
								compilation.assets[asset] = new ConcatSource(output.css);
							});

							if (match) {
								const rtlMinify = cssnano.process(rtlSource, nanoOptions).then(output => {
									compilation.assets[filename] = new ConcatSource(output.css);
									rtlFiles.push(filename);
								});

								minify = Promise.all([minify, rtlMinify]);
							}

							return minify;
						});
					} else if (match) {
						compilation.assets[filename] = new ConcatSource(rtlSource);
						rtlFiles.push(filename);
					}
				});

				cssnanoPromise.then(() => {
					chunk.files.push.apply(chunk.files, rtlFiles)
					cb()
				});
			}, callback);
		});
	}
}

module.exports = RTLCSSPlugin;