// 1-sync.ts

import { readFileSync, writeFileSync } from 'node:fs';

function doThing() {
  writeFileSync('file.txt', 'Hello Sync');
  const CONTENTS = readFileSync('file.txt').toLocaleString('utf8');
  console.log(CONTENTS);
}
doThing();

// 2-callbacks.ts

import { readFile, writeFile } from 'node:fs';

writeFile('file.txt', 'Hello Callback', () => {
  console.log("Okay I'm done");
  readFile('file.txt', (error, contentsOfFile) => {
    console.log(contentsOfFile.toLocaleString('utf-8'));
  });
});
console.log('First or second?');

// 3-promises.ts

import { readFile, writeFile } from 'fs/promises';

const thingPromise = writeFile('file.txt', 'Hello Promises')
  .then(() => readFile('file.txt'))
  .then(fileContents => console.log(fileContents.toLocaleString('utf-8')))
  .catch(err => console.log(`There was an error ${err}`))
  .finally(() => console.log('the very end'));
console.log('This will run UNINTERRUPTED write after the write call is made');

// I could at this point POLL thingPromise to keep asking it
// "hey you done?"

// 4-async.ts

import { readFile, writeFile } from 'fs/promises';

async function doThing() {
  try {
    const writePromise = writeFile('file.txt', 'Hello Async/Await');
    console.log("This can't run until AFTER the file is written");
    const contents = await readFile('file.txt');
    console.log(contents.toLocaleString('utf-8'));
    return contents;
  } catch (e) {
    console.log('Error!');
  }
}
const result = doThing();