const webpack = require('webpack');
const webpackVersion = require('webpack/package.json').version;
const SingleEntryPlugin = require('webpack/lib/SingleEntryPlugin');
const LoaderTargetPlugin = require('webpack/lib/LoaderTargetPlugin');
const WebWorkerTemplatePlugin = require('webpack/lib/webworker/WebWorkerTemplatePlugin');

function getCompilerHook(compiler, {id, entry, filename, chunkFilename, plugins}) {
  return function(compilation, callback) {
    const outputOptions = {
      filename,
      chunkFilename,
      publicPath: compilation.outputOptions.publicPath,
      // HACK: globalObject is necessary to fix https://github.com/webpack/webpack/issues/6642
      globalObject: 'this',
    };
    const childCompiler = compilation.createChildCompiler(id, outputOptions, [
      new WebWorkerTemplatePlugin(),
      new LoaderTargetPlugin('webworker'),
      new SingleEntryPlugin(compiler.context, entry, 'main'),
    ]);
    plugins.forEach((plugin) => plugin.apply(childCompiler));
    childCompiler.runAsChild(callback);
  }
}

class AddWorkerEntryPointPlugin {
  constructor({
    id,
    entry,
    filename,
    chunkFilename = undefined,
    plugins = undefined,
  }) {
    this.options = { id, entry, filename, chunkFilename, plugins };
  }

  apply(compiler) {
    const compilerHook = getCompilerHook(compiler, this.options);
    if (webpackVersion < '4') {
      compiler.plugin('make', compilerHook);
    } else {
      compiler.hooks.make.tapAsync('AddWorkerEntryPointPlugin', compilerHook);
    }
  }
}

module.exports = AddWorkerEntryPointPlugin;