import { Readable, Writable } from "stream";
import { pipeline } from "stream/promises";

class CustomReadable extends Readable {
  constructor(name) {
    super();
    this.name = name;
  }

  _read() {
    console.log(`${this.name}: write hello world`);
    this.push("hello world");
    console.log(`${this.name}: end readable`);
    this.push(null);
  }
}

class CustomWritable extends Writable {
  constructor(name) {
    super();
    this.name = name;
  }

  _write() {
    console.log(`${this.name}: fire write`);
  }

  end() {
    console.log(`${this.name}: fire end`);
  }
}

// comment either one to see the actual flow
// fire end once when using pipe
new CustomReadable("pipe").pipe(new CustomWritable("pipe"));
// fire end twice when using pipeline
await pipeline(new CustomReadable("pipeline"), new CustomWritable("pipeline"));

// pipeline
pipeline: write hello world
pipeline: end readable
pipeline: fire write
pipeline: fire end

// pipe
pipe: write hello world
pipe: end readable
pipe: fire write
pipe: fire end

// pipeline
pipeline: write hello world
pipeline: end readable
pipeline: fire write
pipeline: fire end
pipeline: fire end

// pipe
pipe: write hello world
pipe: end readable
pipe: fire write
pipe: fire end

import { pipeline } from 'stream/promises'
import fs from 'fs'

const { MongoClient, GridFSBucket } = require('mongodb');

const client = await MongoClient.connect(`mongodb://localhost:27017`);

const database = client.db('test01');
const bucket = new GridFSBucket(database, { bucketName: 'test01' });

const readable = fs.createReadStream('/tmp/test.txt');
const writable = bucket.openUploadStream('test.txt')
await pipeline(readable, writable)