// https://javascript.info/async-await

// An async function always returns a promise. Other values are wrapped in a resolved promise automatically.
// Async and await are merely syntactic sugar in order to make Promise usage easier

async function f1 () {
  return 1
}

f1().then(console.log) // 1

// The keyword await makes JavaScript wait until that promise settles and returns its result.
// It can be used in async functions only.
// Let’s emphasize: await literally suspends the function execution until the promise settles,
// and then resumes it with the promise result.
async function f2 () {
  const promise = new Promise((resolve, reject) => {
    setTimeout(() => resolve('done!'), 1000)
  })
  const result = await promise // wait until the promise resolves (*)
  console.log(result) // "done!"
}
f2()

// The code in the same function after "await"
// is to be intended in the "then()" of the promise.
// Consider the following example:
async function exampleAsyncFunction () {
  console.log('Before await')
  await new Promise(function (resolve, reject) {
    console.log("In the Promise")
    setTimeout(() => resolve(), 500)
  }) // Pauses execution here until the promise resolves.
  console.log('After await')
}
console.log('Start')
exampleAsyncFunction()
console.log('End')

/*

The result will be:
Start, Before Await, In the Promise, End, After await
"End" comes before "After Await" because the
flow of execution goes to the caller of exampleAsyncFunction
after setTimeout() gets enqueued in the Event Loop Thread
but before 500ms have elapsed.

+---------------+
| Main          |
+---------------+
       |
       |
       v
+----------------------+
|exampleAsyncFunction  |
+----------------------+
       |
       |
       v
+---------------+
| Promise       |
+---------------+
       |
       |
       v
+----------------------------------------+
|Enqueue resolve() and exit immediately  |                                  +--------------------------------+
+----------------------------------------+ -------------------------------> |Wait 500ms in the libuv library |
       |                                                                    +--------------------------------+
       | Nothing left to do in the AWAIT, return to caller                              |
       v                                                                                |
+---------------+                                                                       |
| Main          |                                                                       |
+---------------+                                                                       |
       |                                                                                |
       |                                                                                |   
       v                                                                                |
+-------------------+                                                                   |
| Then() of Promise |       <-----------------------------------------------------------
+-------------------+                                                                                                                                                                           
                        


*/

// Questions
//
// Why await only works in async function in javascript?
// https://stackoverflow.com/questions/49640647/why-await-only-works-in-async-function-in-javascript
//
// Why using async-await
// https://stackoverflow.com/questions/42624647/why-use-async-when-i-have-to-use-await
//
// Be mindful: it is not possible to create an async function from scratch (such as
// setInterval o fetch)
// https://stackoverflow.com/questions/61857274/how-to-create-custom-asynchronous-function-in-javascript
//
// Another question that may be interesting
// https://stackoverflow.com/questions/42624647/why-use-async-when-i-have-to-use-await