import CopyWebpackPlugin from 'copy-webpack-plugin'
var CommonsChunkPlugin = require('webpack/lib/optimize/CommonsChunkPlugin');

/**
 * Function that mutates original webpack config.
 * Supports asynchronous changes when promise is returned.
 *
 * @param {object} config - original webpack config.
 * @param {object} env - options passed to CLI.
 * @param {WebpackConfigHelpers} helpers - object with useful helpers when working with config.
 **/
export default function (config, env, helpers) {
	if (env.isProd) {
		config.devtool = false; // disable sourcemaps

		const htmlWebpackPlugin = helpers.getPluginsByName(config, 'HtmlWebpackPlugin')[0];
		Object.assign(htmlWebpackPlugin.plugin.options.minify, {
			removeComments: false,
			collapseWhitespace: false
		})

		config.plugins.push(
			new CommonsChunkPlugin({
				name: 'vendor',
				minChunks: ({
					resource
				}) => /node_modules/.test(resource),
			})
		);

		const swPlugin = helpers.getPluginsByName(config, 'SWPrecacheWebpackPlugin')[0];
		config.plugins.splice(swPlugin.index, 1)

		const uglifyPlugin = helpers.getPluginsByName(config, 'UglifyJsPlugin')[0]
		config.plugins.splice(uglifyPlugin.index, 1)
	}

}