const fs = require('fs');
const path = require('path');
const ClosureCompiler = require('google-closure-compiler').compiler;

/**
 * Minify a javascript file
 *
 * @param {string} inputFile
 * @param {string} outputFile
 * @param {object} options
 */
module.exports = function minify(inFile, outFile, options) {
	const defaultOptions = {
		js: inFile,
		js_output_file: outFile,
		compilation_level: 'ADVANCED',
		language_in: 'ECMASCRIPT5',
		language_out: 'ECMASCRIPT5',
		warning_level: 'VERBOSE',
		create_source_map: `${outFile}.map`,
		rewrite_polyfills: false
	};

	options = options || {};
	Object.keys(options).forEach(opt => {
		defaultOptions[opt] = options[opt];
	});

	const compiler = new ClosureCompiler(defaultOptions);

	compiler.run((exitCode, stdOut, stdErr) => {
		if (stdErr) {
			console.error(stdErr);
		} else {
			console.log(stdOut);
		}

		// Append the source map maping line to the minified file
		fs.appendFileSync(outFile, '//# sourceMappingURL=' + path.basename(outFile) + '.map');
	});
};