How does Ruby's rest-client work for OAuth 2? - ruby

Question

I am trying to implement an OAuth 2 sign up for an Angular 6, using gitLab Api. Its website has some code for getting the access token based on Ruby. I will be so glad if anyone lets me know how to get this access token.
OAtuth 2 for gitLab says that I can get the secret code and YOUR_UNIQUE_STATE_HASH. I managed to follow their instruction.
To get the access token, gitLab posted some Rubi [sic] code, which I could not understand and don't know how to implement in angular.
Here is the instruction:
Once you have the authorization code you can request an access_token using the code, to do that you can use any HTTP client. In the following example, we are using Ruby's rest-client:
parameters = 'client_id=APP_ID&client_secret=APP_SECRET&code=RETURNED_CODE&grant_type=authorization_code&redirect_uri=REDIRECT_URI'
RestClient.post 'http://gitlab.example.com/oauth/token', parameters
# The response will be
{
"access_token": "de6780bc506a0446309bd9362820ba8aed28aa506c71eedbe1c5c4f9dd350e54",
"token_type": "bearer",
"expires_in": 7200,
"refresh_token": "8257e65c97202ed1726cf9571600918f3bffb2544b26e00a61df9897668c33a1"
}
I would be so kind if somebody explains this code snippet.

Answer 1

The snippet is basically doing as denoted already. You need to generate the access token (or bearer token) using your client id and client secret with the code which was returned after successful user auth - this access token is basically the token which you will then further use on behalf of user to gitlab.
OAuth makes sure that the client code cannot be used by unauthorized attacker by making sure that you as a developer request it with your client id and client_secret.
RestClient.post 'http://gitlab.example.com/oauth/token', parameters will send that POST request and then Gitlab will return the response with access token and about it's expiry.