Show each wallet's balance in USD

apps/ios/Koins/AppModel.swift

@@ -15,6 +15,8 @@ final class AppModel: ObservableObject {
   @Published var moneroReady = false
   @Published var moneroAddress: String?
   @Published var moneroAccounts: [MoneroAccount] = []
+  @Published var prices = PriceService.Prices()
+
   /// Whether the app is behind the biometric lock screen right now.
   @Published var locked = false
 
@@ -53,6 +55,28 @@ final class AppModel: ObservableObject {
 
   var symbol: String { chain.symbol }
 
+  // MARK: - Fiat display
+
+  private static let fiatFormatter: NumberFormatter = {
+    let formatter = NumberFormatter()
+    formatter.numberStyle = .currency
+    formatter.currencyCode = "USD"
+    formatter.locale = Locale(identifier: "en_US")
+    return formatter
+  }()
+
+  /// The current chain's balance in USD, when a price is known.
+  var fiatBalance: String? {
+    let price = chain == .xrp ? prices.xrp : prices.xmr
+    guard let price, let amount = Decimal(string: balance.total) else { return nil }
+    let usd = amount * Decimal(price)
+    return Self.fiatFormatter.string(from: usd as NSDecimalNumber)
+  }
+
+  private func refreshPrices() async {
+    prices = await PriceService.shared.prices()
+  }
+
   // MARK: - Biometric lock
 
   func authenticate() async {
@@ -112,6 +136,7 @@ final class AppModel: ObservableObject {
     showCached(chain)
     await refresh(force: true)
     startAutoRefresh()
+    Task { await refreshPrices() }
   }
 
   private func adoptMoneroWallet(named name: String) async {
@@ -263,6 +288,7 @@ final class AppModel: ObservableObject {
     refreshToken = token
     let requestChain = chain
     errorMessage = nil
+    await refreshPrices()
     if chain == .xrp, let wallet = xrpWallet {
       do {
         async let balanceCall = XRPWalletService.shared.balance(address: wallet.address)