AndroidAppleSignIn

Sign in with Apple on Android. There is no native SDK — this is Apple's OAuth web flow, and it needs a server. AppleSiwaServer documents exactly which server, and why no client-only path exists once you ask for name and email.

Deliberately not a SocialSignIn: that interface promises a suspend fun that resumes with a result, and this flow leaves the app for a browser and returns through a deep link into a possibly brand-new process. A suspend wrapper around it would be a coroutine that sometimes never resumes — a hang with no error, which is worse than an API that admits it has two halves.

// 1. sign-in button
when (val start = appleSignIn.begin()) {
    is AppleWebStart.Launched -> settings.putString("apple_pending", start.pending.encode())
    is AppleWebStart.Unavailable -> hideAppleButton(start.reason)   // never draw a dead button
}

// 2. the Activity your server's 302 lands in (android:autoVerify App Link)
val pending = settings.getStringOrNull("apple_pending")?.let(AppleWebPending::decode)
val outcome = pending?.let { appleSignIn.complete(it, intent.data.toString()) }
settings.remove("apple_pending")   // single use: a replayed state is a state to reject

The app link that receives the bounce must be declared in the host app's manifest with android:autoVerify="true" and a matching assetlinks.json on the domain. Without verification Android shows a disambiguation dialog, and any other installed app may claim the same URL.

ponytail: opens the user's browser with ACTION_VIEW rather than a Custom Tab. A Custom Tab looks better and shares the browser's Apple session, but costs an androidx.browser dependency this module does not otherwise need. Swap it in the host app if the polish is worth the artifact — and never swap in a WebView: an embedded WebView can read the user's Apple password.