Initial donation amount picker

Co-authored-by: trevor-signal <131492920+trevor-signal@users.noreply.github.com>

ts/util/subscriptionConfiguration.ts

@@ -0,0 +1,43 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { SubscriptionConfigurationResultType } from '../textsecure/WebAPI';
+import type { OneTimeDonationHumanAmounts } from '../types/Donations';
+import { HOUR } from './durations';
+import { isInPast } from './timestamp';
+
+const SUBSCRIPTION_CONFIG_CACHE_TIME = HOUR;
+
+let cachedSubscriptionConfig: SubscriptionConfigurationResultType | undefined;
+let cachedSubscriptionConfigExpiresAt: number | undefined;
+
+export async function getCachedSubscriptionConfiguration(): Promise<SubscriptionConfigurationResultType> {
+  if (
+    cachedSubscriptionConfigExpiresAt != null &&
+    isInPast(cachedSubscriptionConfigExpiresAt)
+  ) {
+    cachedSubscriptionConfig = undefined;
+  }
+
+  if (cachedSubscriptionConfig != null) {
+    return cachedSubscriptionConfig;
+  }
+
+  const { server } = window.textsecure;
+  if (!server) {
+    throw new Error('getSubscriptionConfiguration: server is not available');
+  }
+
+  const response = await server.getSubscriptionConfiguration();
+
+  cachedSubscriptionConfig = response;
+  cachedSubscriptionConfigExpiresAt =
+    Date.now() + SUBSCRIPTION_CONFIG_CACHE_TIME;
+
+  return response;
+}
+
+export async function getDonationHumanAmounts(): Promise<OneTimeDonationHumanAmounts> {
+  const { currencies } = await getCachedSubscriptionConfiguration();
+  return currencies;
+}