AndroidReplacementMode enum

Android Replacement Mode (formerly Proration Mode)

IMPORTANT: Replacement modes are ONLY for upgrading/downgrading EXISTING subscriptions. For NEW subscriptions, do NOT use any replacement mode.

To use replacement mode:

1. User must have an active subscription
2. You must provide the purchaseToken from the existing subscription
3. Get the token using getAvailablePurchases()

Example:

// First, check for existing subscription
final purchases = await FlutterInappPurchase.instance.getAvailablePurchases();
if (purchases.isEmpty) {
  // User has no subscription - purchase new one WITHOUT replacement mode
  await FlutterInappPurchase.instance.requestPurchaseWithBuilder(
    build: (builder) {
      builder.type = ProductQueryType.Subs;
      builder.android.skus = ['premium_monthly'];
    },
  );
} else {
  // User has subscription - can upgrade/downgrade WITH replacement mode
  final existingSub = purchases.first;
  await FlutterInappPurchase.instance.requestPurchaseWithBuilder(
    build: (builder) {
      builder.type = ProductQueryType.Subs;
      builder.android
        ..skus = ['premium_yearly']
        ..purchaseTokenAndroid = existingSub.purchaseToken
        ..replacementModeAndroid =
            AndroidReplacementMode.withTimeProration.value;
    },
  );
}