Cache wallet balance and activity so screens show it instantly

apps/ios/Koins/AppModel.swift

@@ -41,6 +41,27 @@ final class AppModel: ObservableObject {
 
   var symbol: String { chain.symbol }
 
+  // MARK: - Cache
+
+  /// Restores the last-known state for the chain on screen instantly; the
+  /// refresh that follows replaces it with live data.
+  private func showCached(_ forChain: Chain) {
+    guard let cached = WalletStore.cachedState(forChain) else { return }
+    balance = cached.balance
+    transactions = cached.transactions
+    if let accounts = cached.accounts { moneroAccounts = accounts }
+  }
+
+  private func persistState(for forChain: Chain) {
+    guard (forChain == .xrp ? xrpWallet : xmrWallet) != nil else { return }
+    WalletStore.saveCachedState(
+      ChainCache(balance: balance,
+                 transactions: transactions,
+                 accounts: forChain == .xmr ? moneroAccounts : nil,
+                 savedAt: Date()),
+      chain: forChain)
+  }
+
   // MARK: - Bootstrap
 
   func bootstrap() async {
@@ -57,6 +78,7 @@ final class AppModel: ObservableObject {
     if xrpWallet != nil || moneroReady {
       chain = xrpWallet != nil ? .xrp : .xmr
     }
+    showCached(chain)
     await refresh(force: true)
     startAutoRefresh()
   }
@@ -101,7 +123,9 @@ final class AppModel: ObservableObject {
     statusMessage = nil
     balance = Balance(total: "0", unlocked: "", funded: false)
     transactions = []
+    moneroAccounts = []
     syncStatus = nil
+    showCached(newChain)
 
     if newChain == .xmr, let xmrWallet, !moneroOpened {
       await openMonero(afterRestore: false, wallet: xmrWallet)
@@ -217,6 +241,7 @@ final class AppModel: ObservableObject {
         guard !isStale(token, requestChain) else { return }
         balance = fetchedBalance
         transactions = fetchedTransactions
+        persistState(for: requestChain)
       } catch {
         guard !isStale(token, requestChain) else { return }
         errorMessage = error.localizedDescription
@@ -251,6 +276,7 @@ final class AppModel: ObservableObject {
         balance = fetchedBalance
         transactions = fetchedTransactions
         moneroAccounts = fetchedAccounts
+        persistState(for: requestChain)
       }
     } catch {
       guard !isStale(token, requestChain) else { return }