const stream = require('stream');
const fs = require('fs');
const path = require('path');
const mkdirp = require('mkdirp');

class ToFileStream extends stream.Writable {
  constructor() {
    super({ objectMode: true });                            // [1]
  }

  _write(chunk, encoding, callback) {                       // [2]
    mkdirp(path.dirname(chunk.path), (err) => {
      if(err) {
        callback(err);
      }
      fs.writeFile(chunk.path, chunk.content, callback);
    })
  }
}

const tfs = new ToFileStream();

tfs.write({
  path: './fileCreatorFiles/file1.txt',
  content: 'Hello'
});

tfs.write({
  path: './fileCreatorFiles/file2.txt',
  content: 'Nodejs'
});

tfs.write({
  path: './fileCreatorFiles/file3.txt',
  content: 'Streams!'
});

tfs.end(() => {
  console.log('All files created');
})

// [1] `objectMode` true to allow writable stream to accept object data type.
//     Other acceptable arguments:
//       - `highWaterMark`: controls internal buffer limit
//       - `decodeStrings`: enables automatic decoding of strings into binary
//          buffers before passing to _write() method. Defaults to true
//
// [2] the _write() implementation accepts a callback which is invoked when
//     the operation completes. It is not necessary to pass the result to
//     callback; but we can pass an error which will cause the stream to
//     emit an `error` event.