Support changing just the currency of an existing subscription

service/src/main/java/org/whispersystems/textsecuregcm/controllers/SubscriptionController.java

@@ -516,16 +516,19 @@ public class SubscriptionController {
                   // and needs to call create_payment_method to create a customer for the given payment method
                   new ClientErrorException(Status.CONFLICT));
 
-            final String subscriptionTemplateId = getSubscriptionTemplateId(level, currency, processorCustomer.processor());
+          final String subscriptionTemplateId = getSubscriptionTemplateId(level, currency,
+              processorCustomer.processor());
 
           final SubscriptionProcessorManager manager = getManagerForProcessor(processorCustomer.processor());
 
-            return Optional.ofNullable(record.subscriptionId)
+          return Optional.ofNullable(record.subscriptionId).map(subId -> {
-                    .map(subId -> {
+            // we already have a subscription in our records so let's check the level and currency,
-                        // we already have a subscription in our records so let's check the level and change it if needed
+            // and only change it if needed
             return manager.getSubscription(subId).thenCompose(
-                                subscription -> manager.getLevelForSubscription(subscription).thenCompose(existingLevel -> {
+                subscription -> manager.getLevelAndCurrencyForSubscription(subscription)
-                                    if (level == existingLevel) {
+                    .thenCompose(existingLevelAndCurrency -> {
+                      if (existingLevelAndCurrency.equals(new SubscriptionProcessorManager.LevelAndCurrency(level,
+                          currency.toLowerCase(Locale.ROOT)))) {
                         return CompletableFuture.completedFuture(subscription);
                       }
                       return manager.updateSubscription(
@@ -541,9 +544,6 @@ public class SubscriptionController {
                 record.subscriptionCreatedAt != null ? record.subscriptionCreatedAt.getEpochSecond() : 0;
 
             // we don't have a subscription yet so create it and then record the subscription id
-                      //
-                      // this relies on stripe's idempotency key to avoid creating more than one subscription if the client
-                      // retries this request
             return manager.createSubscription(processorCustomer.customerId(),
                     subscriptionTemplateId,
                     level,

service/src/main/java/org/whispersystems/textsecuregcm/subscriptions/BraintreeManager.java

@@ -358,11 +358,13 @@ public class BraintreeManager implements SubscriptionProcessorManager {
   }
 
   @Override
-  public CompletableFuture<Long> getLevelForSubscription(Object subscriptionObj) {
+  public CompletableFuture<LevelAndCurrency> getLevelAndCurrencyForSubscription(Object subscriptionObj) {
     final Subscription subscription = getSubscription(subscriptionObj);
 
     return findPlan(subscription.getPlanId())
-        .thenApply(this::getLevelForPlan);
+        .thenApply(
+            plan -> new LevelAndCurrency(getLevelForPlan(plan), plan.getCurrencyIsoCode().toLowerCase(Locale.ROOT)));
+
   }
 
   private CompletableFuture<Plan> findPlan(String planId) {

service/src/main/java/org/whispersystems/textsecuregcm/subscriptions/StripeManager.java

@@ -246,6 +246,8 @@ public class StripeManager implements SubscriptionProcessorManager {
   @Override
   public CompletableFuture<SubscriptionId> createSubscription(String customerId, String priceId, long level,
       long lastSubscriptionCreatedAt) {
+    // this relies on Stripe's idempotency key to avoid creating more than one subscription if the client
+    // retries this request
     return CompletableFuture.supplyAsync(() -> {
           SubscriptionCreateParams params = SubscriptionCreateParams.builder()
               .setCustomer(customerId)
@@ -274,9 +276,7 @@ public class StripeManager implements SubscriptionProcessorManager {
   public CompletableFuture<SubscriptionId> updateSubscription(
           Object subscriptionObj, String priceId, long level, String idempotencyKey) {
 
-    if (!(subscriptionObj instanceof final Subscription subscription)) {
+    final Subscription subscription = getSubscription(subscriptionObj);
-      throw new IllegalArgumentException("invalid subscription object: " + subscriptionObj.getClass().getName());
-    }
 
     return CompletableFuture.supplyAsync(() -> {
               List<SubscriptionUpdateParams.Item> items = new ArrayList<>();
@@ -400,12 +400,12 @@ public class StripeManager implements SubscriptionProcessorManager {
   }
 
   @Override
-  public CompletableFuture<Long> getLevelForSubscription(Object subscriptionObj) {
+  public CompletableFuture<LevelAndCurrency> getLevelAndCurrencyForSubscription(Object subscriptionObj) {
-    if (!(subscriptionObj instanceof final Subscription subscription)) {
+    final Subscription subscription = getSubscription(subscriptionObj);
 
-      throw new IllegalArgumentException("Invalid subscription object: " + subscriptionObj.getClass().getName());
+    return getProductForSubscription(subscription).thenApply(
-    }
+        product -> new LevelAndCurrency(getLevelForProduct(product), subscription.getCurrency().toLowerCase(
-    return getProductForSubscription(subscription).thenApply(this::getLevelForProduct);
+            Locale.ROOT)));
   }
 
   public CompletableFuture<Long> getLevelForPrice(Price price) {

service/src/main/java/org/whispersystems/textsecuregcm/subscriptions/SubscriptionProcessorManager.java

@@ -47,7 +47,11 @@ public interface SubscriptionProcessorManager {
   CompletableFuture<SubscriptionId> updateSubscription(
       Object subscription, String templateId, long level, String idempotencyKey);
 
-  CompletableFuture<Long> getLevelForSubscription(Object subscription);
+  /**
+   * @param subscription
+   * @return the subscription’s current level and lower-case currency code
+   */
+  CompletableFuture<LevelAndCurrency> getLevelAndCurrencyForSubscription(Object subscription);
 
   CompletableFuture<Void> cancelAllActiveSubscriptions(String customerId);
 
@@ -160,4 +164,8 @@ public interface SubscriptionProcessorManager {
 
   }
 
+  record LevelAndCurrency(long level, String currency) {
+
+  }
+
 }

service/src/test/java/org/whispersystems/textsecuregcm/controllers/SubscriptionControllerTest.java

@@ -72,7 +72,6 @@ import org.whispersystems.textsecuregcm.subscriptions.StripeManager;
 import org.whispersystems.textsecuregcm.subscriptions.SubscriptionProcessor;
 import org.whispersystems.textsecuregcm.subscriptions.SubscriptionProcessorManager;
 import org.whispersystems.textsecuregcm.tests.util.AuthHelper;
-import org.whispersystems.textsecuregcm.util.Pair;
 import org.whispersystems.textsecuregcm.util.SystemMapper;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
 
@@ -548,7 +547,8 @@ class SubscriptionControllerTest {
     when(BRAINTREE_MANAGER.getSubscription(any()))
         .thenReturn(CompletableFuture.completedFuture(subscriptionObj));
     when(BRAINTREE_MANAGER.getLevelAndCurrencyForSubscription(subscriptionObj))
-        .thenReturn(CompletableFuture.completedFuture(new Pair<>(existingLevel, existingCurrency)));
+        .thenReturn(CompletableFuture.completedFuture(
+            new SubscriptionProcessorManager.LevelAndCurrency(existingLevel, existingCurrency)));
     final String updatedSubscriptionId = "updatedSubscriptionId";
 
     if (expectUpdate) {