Firebase cloud messaging: Request contains an invalid argument - node.js

Question

I'm following this tutorial, I got to the point to send an HTTP request to the fcm endpoint, but I'm getting the following error:
{
error:
{
code: 400,
message: 'Request contains an invalid argument.',
status: 'INVALID_ARGUMENT'
}
}
Instead of sending the request using curl I'm using a cloud function using node.js | express with the following code:
exports.messages = function (req, res) {
const api = 'https://fcm.googleapis.com/v1/projects/myproject-b5ae1/messages:send';
const headers = {
'Accept': 'application/json',
'Content-type': 'application/json',
};
return getAccessToken().then((accessToken) => {
headers.Authorization = `Bearer ${accessToken}` // <-- accessToken is OK
const { title, body, token } = req.body;
return fetch(api, {
headers,
method: 'POST',
body: JSON.stringify(
{
'message': {
'token': token, // <-- this is the client fcm token
'notification': {
'title': title,
'body': body
}
}
}
)
}).then(res => res.json()).then(data => {
console.log(data);
res.sendStatus(200);
}).catch((error) => {
console.error(error);
});
});
}
Where the token is an OAuth 2 token for my service account
function getAccessToken() {
return new Promise(function (resolve, reject) {
var key = require('../keys/service-account.json');
var jwtClient = new google.auth.JWT(
key.client_email,
null,
key.private_key,
[
'https://www.googleapis.com/auth/firebase',
'https://www.googleapis.com/auth/firebase.database',
'https://www.googleapis.com/auth/firebase.messaging',
],
null
);
jwtClient.authorize(function (err, tokens) {
if (err) {
reject(err);
return;
}
resolve(tokens.access_token);
});
});
}
what am I missing here? any advice will be appreciated

Answer 1

I just realized I copied the uri for the fcm endpoint from the tutorial. I changed it to:
const api = 'https://fcm.googleapis.com/v1/projects/{project-Id}/messages:send';
and it worked!