How to create loopback external CRUD? - node.js

Question

I want to use loopback to be a "middle man" to connect between two different api (server1 and server2). When I pass a user's email to this "middle man", it will check with server 1, and if that server returns true, then the "middle man" will get all data from the server 2 save to server 1.
Can someone guide me on how to do this? I tried to follow loopback documentation, but I couldn't get what I want, am I missing something?

Answer 1

So the actual implementation is not really related to Loopback.js framework. This can be implemented in any Node.js code.
And actually your description above is the the right steps to do it using a simple HTTP request to server 1 and 2
For example using request
module this code shows the pseudocode of the middle man.
const request = require('request');
// 1. Call Server 1
request('http://server1.com/api/message', function (err, res, body) {
// 2. Check body message is true
if (body.message === true) {
// 3. Get data from Server 2
request('http://server2.com/api/get', function (err, res, body) {
// 4. Save data to Server 1
request({
url: 'http://server1.com/api/save',
method: "POST",
json: requestData },
function (err, res body) { /* process response here... */ });
});
}
});

Answer 2

Assuming you have set up two datasources that call your external API providers as per my answer to your related question - for this example you would need the following calls:
Server1 datasource:
checkEmail // GET method, returns true or false
save // POST method, returns true or false
Server2 datasource:
getDetails // GET or POST method, returns contact details for the email address
You would also need a Loopback Model with an appropriate method as your entry point. For the example lets call it Contact, with a remote method called store, taking in the email parameter. This code would do all of the work:
Contact.store = function(email, cb) {
var server1 = Contact.app.dataSources.Server1;
var server2 = Contact.app.dataSources.Server2;
server1.checkEmail(email, function(validated) {
if(validated) {
server2.getDetails(email, function(details) {
if(details) {
server1.save(details, function(success) {
if(success) {
cb(null, details);
}
})
}
})
}
})
}
(you can promisify all of the above for cleaner code)