/*** BROSWER W/ FETCH API ***/
/*
    Let's say that we're posting credentials to some API,
    and then performing a get request to some protected resource
    with the credentials (i.e. cookie, JWT, etc.) that is returned
    to us from the first API call
*/

var firstApiUrl = ''
fetch(firstApiUrl, {
    method: 'POST',
    body: JSON.strinfiy({username: '', password: ''})
}).then(function(res) {
    var apiKey = JSON.parse(res.data)

    // fetch returns a promise, so we can continue chaining
    var secondApiUrl = ''
    return fetch(secondApiUrl + '?key=' + apiKey, { method: 'GET' })
}).then(function(res) {
    var data = JSON.parse(res.data)

    // This illustrates an explicit return of a promise
    return new Promise(function(resolve, reject) {
        resolve("Hi Charlie!")
    })
}).then(function(value){
    // Value here is what the last promise resovled as so
    console.log(value) // "Hi Charlie!"

    // Now let's throw an error
    return new Promise(function(reoslve, reject) {
        reject(new Error('Sad face :('))
    })
}).catch(function(err) {
    // This catches the error at any point in the promise chain
    // but let's assume they all resolved except the last .then where we rejected w/ an error

    console.log('Error performing API call(s)', err) // 'Error performing api Call(s) Sad face :('
})


/*** NODE CALLBACKS ***/

// this is an imaginary rest client, the point is that it uses callbacks in our imaginary api
var rest = require('')

rest.post(firstApiUrl, JSON.stringify({username: '', password: ''}), function callback(err, res) {
    if (err) {
        console.log('Error!', err)
        // return to prevent next api from being called
        return
    }

    rest.get(secondApiUrl, function(err, res) {
        if (err) {
            // we have to handle errors at every step, unlike promises
            console.log('Error!', err)
            return
        }

        // another async function
        databaseClient.write(res.data, function(err) {
            if (err) {
                console.log('Error writing to database', err)
            }
        })
    })