const webpack = require("webpack");
const Vinyl = require("vinyl");
const MemoryFs = require("memory-fs");
const { Transform } = require("stream");
const path = require("path");

class Webpack extends Transform {
  constructor(outputPath) {
    super({
      objectMode: true
    });
    this.outputPath = outputPath;
  }

  _transform(file, encoding, done) {
    const compiler = webpack({
      entry: file.path,
      output: {
        path: "/build",
        filename: "bundle.js"
      },
      module: {
        rules: [
          {
            test: /\.jsx?$/,
            exclude: /node_modules/,
            loader: "babel-loader",
            options: {
              presets: [
                "react",
                "flow"
              ]
            }
          }
        ]
      }
    });
    const fs = new MemoryFs();
    compiler.outputFileSystem = fs;
    const self = this;
    compiler.plugin("after-emit", (compilation, callback) => {
      fs.readFile("/build/bundle.js", (err, data) => {
        if (err) {
          console.error(err);
          return;
        }
        self.push(new Vinyl({
          cwd: process.cwd(),
          path: self.outputPath,
          contents: Buffer.from(data, "utf8")
        }));
        callback();
      });
    });
    compiler.run((err, stats) => {
      if (err) {
        console.error(err);
      }
      done();
    });
  }
}

module.exports = (outputPath) => {
  return new Webpack(outputPath);
};