// Get DOM elements

const generateButton = document.getElementById('generate-button');

const postTitle = document.getElementById('post-title');

const postId = document.getElementById('post-id');

const postContent = document.getElementById('post-content');

/**

* Makes an AJAX request of type 'verb' to 'url' with optional 'data' object

* Returns a Promise which resolves or rejects with server response

*/

function makeRequest(verb, url, data) {

return new Promise((resolve, reject) => {

// create and open AJAX request

let request = new XMLHttpRequest();

request.open(verb, url);

request.onreadystatechange = () => {

// only execute code if request is ready

if (request.readyState === 4) {

// request is successful for codes 200 or 201

if (request.status === 200 || request.status === 201) {

resolve(JSON.parse(request.response));

} else {

reject(JSON.parse(request.response));

}

}

};

// for POST requests, set Content-Type header and send request with 'data` object

// otherwise, simply send request

if (verb === 'POST') {

request.setRequestHeader('Content-Type', 'application/json');

request.send(JSON.stringify(data));

} else {

request.send();

}

});

}

/**

* Sends GET requests for uid, title and content in parallel

* Sends resulting object as POST request

* Handles response from POST request and prints result to DOM

*/

async function createPost() {

// create three request Promises (starts sending requests)

const uidPromise = makeRequest('GET', 'http://ec2-54-70-181-124.us-west-2.compute.amazonaws.com:3000/generate-uid');

const titlePromise = makeRequest('GET', 'http://ec2-54-70-181-124.us-west-2.compute.amazonaws.com:3000/generate-title');

const contentPromise = makeRequest('GET', 'http://ec2-54-70-181-124.us-west-2.compute.amazonaws.com:3000/generate-lorem');

// await responses from three requests and assign to three constants

const [uidResponse, titleResponse, contentResponse] = await Promise.all([uidPromise, titlePromise, contentPromise]);

// concatenate data from GET requests and make POST request

const postPromise = makeRequest('POST',

'http://ec2-54-70-181-124.us-west-2.compute.amazonaws.com:3000/create-post-with-uid',

{ uid: uidResponse.uid, title: titleResponse.title, content: contentResponse.lorem }

);

// assign result to constant and print constant properties to DOM

const postResponse = await postPromise;

postTitle.textContent = postResponse.post.title;

postId.textContent = postResponse.post.id;

postContent.textContent = postResponse.post.content

}

// click listener for Generate Post! button

generateButton.addEventListener('click', () => {

createPost();

});