const closureCompiler = require('google-closure-compiler').gulp(),
  concat = require('gulp-concat'),
  gulp = require('gulp'),
  path = require('path'),
  workers = [];

class JSWorker {
  constructor(config, helper) {
    this.config = config;
    this.helper = helper.clone();
    if (!this.config.name) {
      throw Error("Found Empty name for JS Job...");
    }
    this.validateConfig();
    this.input = this.helper.replaceVariables(this.config.input);
    this.helper.addConfigItem("$name", this.config.name);
    this.helper.addConfigItem("$", this.input);
    this.getCompilerConfig();
    this.out = this.helper.replaceVariables(this.config.output);
    this.watch = this.helper.replaceVariables(this.config.watch || '$/**/*.js');
    this.prepareFiles(this.config.files)
    this.path = path.parse(this.out);
    this.path = this.path.dir + "/" + this.path.base + "/";
    gulp.task(this.taskName, this.work.bind(this));
  }

  validateConfig() {
    let config = this.config;
    config.onlyMinify = config.onlyMinify || false;
    config.minify = config.minify || false;
    if (!this.config.input || !this.config.output || !this.config.files) {
      throw Error("Invalid Config for: " + this.config.name + ")");
    }
  }

  getCompilerConfig() {
    this.compiler = {
      compilation_level: 'SIMPLE',
      warning_level: 'VERBOSE',
      language_in: 'ECMASCRIPT6_STRICT',
      language_out: 'ECMASCRIPT6_STRICT',
      js_output_file: this.config.name + ".min.js"
    }
    if (this.config.compiler) {
      this.compiler = Object.assign(this.compiler, this.config.compiler);
    }
    this.compiler.js_output_file = this.helper.replaceVariables(this.compiler.js_output_file);
  }

  startWatch() {
    gulp.watch([this.watch, ...this.files], gulp.parallel([this.taskName]));
  }

  get taskName() {
    return `js-${this.config.name}`;
  }

  prepareFiles(files) {
    this.files = [];
    for (const file of files) {
      this.files.push(this.input + "/" + this.helper.replaceVariables(file));
    }
  }

  work() {
    let d = gulp.src(this.files).pipe(concat(this.config.name + '.js'))
    if (!this.config.onlyMinify) {
        d.pipe(gulp.dest(this.path.dir));
    }
    if (this.config.minify) {
      d.pipe(closureCompiler(this.compiler)).pipe(gulp.dest(this.path.dir));
    }
    return d;
  }
}

module.exports = {
  build: function () {
    let array = [];
    for (let worker of workers) {
      array.push(worker.taskName);
    }
    return array;
  },
  prepare: function (config) {
    // we load the json and parse it here
    const js = config.js || [];
    for (let jsConfig of js) {
      const worker = new JSWorker(jsConfig, config.helper);
      workers.push(worker);
    }
  },
  startWatch: function () {
    for (let worker of workers) {
      worker.startWatch();
    }
  }
}