'use strict';

const config = require('./config');
if (!config.javascript) return;

const gulp = require('gulp');
const sourcemaps = require('gulp-sourcemaps');
const rename = require("gulp-rename");
const notify = require('gulp-notify');
const concat = require('gulp-concat');
const babel = require('gulp-babel');
const plumber = require('gulp-plumber');
const fs = require('fs');
const rollup = require('rollup-stream'); // specifically for rollup
const source = require('vinyl-source-stream'); // specifically for rollup
const buffer = require('vinyl-buffer'); // specifically for rollup
const eslintRollup = require('rollup-plugin-eslint'); // specifically for rollup
const eslint = require('gulp-eslint');
const orderOfJavaScript = require('./_order-of-javascript.js');
const reportErrorsForJavaScript = require('./_report-errors-for-javascript.js');



const javascriptTask = function() {



	// package.json contains information about project
	// no try catch - fail dramatically if package.json is not present
	const pkgAll = fs.readFileSync('./../../package.json', 'utf8');



	// covert string to object
	const pkg = JSON.parse(pkgAll);



	// developer choosing old school approach
	const traditional = function(order) {



			// see if developer needs js files compiled in a specific order
			const queuedJavaScript = orderOfJavaScript(order);



			// then add all other JS files
			queuedJavaScript.push('src/**/*.js');



			return gulp.src(queuedJavaScript)



				.pipe(eslint())



				.pipe(plumber())



				.pipe(notify(reportErrorsForJavaScript))



				.pipe(eslint.format());



	};



	// rollup setup
	const newThreads = function( src ) {



		// fail dramatically if _rollup.js is not present
		fs.readFileSync( 'src/_rollup.js', 'utf8' );



		// get rolling
		return rollup({
				input: src, // look at this specific file src/_rollup.js
				format: 'iife', // automatically encapsulates code in an iife and invokes strict mode
				sourcemap: true, // locate the line number where the issue is occurring
				plugins: [
					eslintRollup({
						"parserOptions": {
							"sourceType": "module" // tell ESLint ES6 modules are in play
						}
					})
				]
			})



			// point to the entry file again
			.pipe(source(src))



			// output the buffer, rollup doesn't support streams
			.pipe(buffer());



	};



	// if rollup in play throw on some new threads
	// otherwise go old school
	return (  pkg.rollup ? newThreads('src/_rollup.js') : traditional(pkg.orderofjavascript)  )



		.pipe(rename(function(path) {
			path.dirname = "";
		}))



		.pipe(sourcemaps.init({ loadMaps: true }))



		.pipe(babel({
			"presets": [
				["env", {
					"targets": {
						"browsers": config.sass.settings
					},
					"modules": false
				}]
			]
		}))



		.pipe(concat('main.js'))



		.pipe(sourcemaps.write('/'))



		.pipe(gulp.dest(config.javascript.dest))



		.pipe(browserSync.stream());



};

gulp.task('javascript', javascriptTask);
module.exports = javascriptTask;