[hencq]

First off, congratulations on launching! I'm not sure why you're getting downvoted, because it seems quite relevant to the discussion. I'll definitely look at btn.social for my next hobby project. The pricing is super reasonable and the documentation very clear.

One question I have around OAuth in general is whether it only applies for SPAs or if I could also use it for more traditional multi-page apps? I guess I could do something similar to what you're doing in your guide [0] and do a POST from the onlogin callback, but how does my backend know that the payload is valid?

[0] https://docs.btn.social/guides/#link-a-payload-with-a-db-rec...

[lukeed]

Thank you! Not sure, just part of the orange site mystery~

Your `onlogin` callback will only ever be invoked by the SDK on successful login. So the data coming thru there is always the result of the OAuth flow itself. For MPAs, you can create your own document cookie and/or modify local/sessionStorage, and then every new page load will pull/load from those storage systems. SPAs can & should do the same – they just have the added benefit of keeping in-memory state alive.

As for POSTing to your backend, the same XSRF/CSRF/CORS rules & mechanisms apply as with any other client->server transaction. You can rely on CORS for limiting who can talk to your API, you can pass along a unique token for CSRF prevention, and/or come up with your own Authorization header format.

Soon I'll be adding a `redirect_uri` config option for all btn.social apps. Much like the normal `redirect_uri` in OAuth, this will be a target URL that btn.social redirects users to post-login. This will enable server-side redirects, which means that your API just has to verify the "login.btn.social" referer.

[hencq]

Ah great, thanks! It would be great to see a larger example on your site to see how this all ties together. For example, I don't really understand what's stopping anyone from opening dev console and just calling my 'onlogin' callback and passing it fake data to impersonate another user. It seems to me that somewhere I'd still need to verify the user data with the provider.

I fully realize that that's probably due to my own ignorance and no knock on you. However, maybe there's others like me who'd benefit from some more examples.

[lukeed]

For sure! There are some larger examples coming so that people can see it plugged into a more real-world application.

RE: onlogin, that method accepts a callback handler that is added to an internal/private array of callbacks to run once the `popup` or `redirect` sequence has finalized. It's the only externally-facing "doorway" into the OAuth flow. Everything else is inciting action (`popup()` and `redirect()`) or a read-out of the last-known payload (`last()`). It's actually very similar to a state manager I wrote a while back[1]. Callbacks are added via `$.on()` which assembles an internal `tree` map to be `dispatch`d once a change happens.

You've probably already seen the API docs for the btn.social SDK, but linking just in case[2]

[1]: https://github.com/lukeed/vegemite/blob/master/src/index.js

[2]: https://docs.btn.social/usage/#methods

[hencq]

Thanks!