[#1371] Improve Balances widget loader logic

- Closes #1371
- This also covers the security audit recommendation: 4.2.14 (App) This comment in WalletSnapshot.kt should be ticketed

CHANGELOG.md

@@ -11,6 +11,7 @@ directly impact users rather than highlighting other key architectural updates.*
 
 ### Fixed
 - Sending zero funds is allowed only for shielded recipient address type
+- The Balances widget loader has been improved to better handle cases, like a wallet with only transparent funds
 
 ## [0.2.0 (609)] - 2024-04-18
 

ui-lib/src/main/java/co/electriccoin/zcash/ui/common/model/WalletSnapshot.kt

@@ -34,6 +34,8 @@ data class WalletSnapshot(
     val isSendEnabled: Boolean get() = hasSaplingFunds && hasOrchardFunds
 }
 
+// TODO [#1370]: WalletSnapshot.canSpend() calculation limitation
+// TODO [#1370]: https://github.com/Electric-Coin-Company/zashi-android/issues/1370
 // Note this check is not entirely correct - it does not calculate the resulting fee using the new Proposal API. It's
 // fine for now, but it's subject to improvement later once we figure out how to handle it in such cases.
 fun WalletSnapshot.canSpend(amount: Zatoshi): Boolean = spendableBalance() >= amount
@@ -48,5 +50,9 @@ fun WalletSnapshot.spendableBalance() = orchardBalance.available + saplingBalanc
 // Note that summing both values could be confusing, and we might prefer dividing them in the future
 fun WalletSnapshot.changePendingBalance() = orchardBalance.changePending + saplingBalance.changePending
 
+fun WalletSnapshot.hasChangePending() = changePendingBalance().value > 0L
+
 // Note that summing both values could be confusing, and we might prefer dividing them in the future
 fun WalletSnapshot.valuePendingBalance() = orchardBalance.valuePending + saplingBalance.valuePending
+
+fun WalletSnapshot.hasValuePending() = valuePendingBalance().value > 0L

ui-lib/src/main/java/co/electriccoin/zcash/ui/common/viewmodel/WalletViewModel.kt

@@ -32,6 +32,7 @@ import co.electriccoin.zcash.ui.common.extension.throttle
 import co.electriccoin.zcash.ui.common.model.OnboardingState
 import co.electriccoin.zcash.ui.common.model.WalletRestoringState
 import co.electriccoin.zcash.ui.common.model.WalletSnapshot
+import co.electriccoin.zcash.ui.common.model.hasChangePending
 import co.electriccoin.zcash.ui.common.model.spendableBalance
 import co.electriccoin.zcash.ui.common.model.totalBalance
 import co.electriccoin.zcash.ui.preference.EncryptedPreferenceKeys
@@ -242,34 +243,32 @@ class WalletViewModel(application: Application) : AndroidViewModel(application)
             )
 
     /**
-     * A flow of the wallet balances state used for the UI layer. It combines [WalletSnapshot] with
-     * [WalletRestoringState] and provides the correct [BalanceState] UI state.
+     * A flow of the wallet balances state used for the UI layer. It's computed form [WalletSnapshot]'s properties
+     * and provides the result [BalanceState] UI state.
      */
     val balanceState: StateFlow<BalanceState> =
         walletSnapshot
             .filterNotNull()
-            .combine(walletRestoringState) {
-                    walletSnapshot: WalletSnapshot, walletRestoringState: WalletRestoringState ->
-                when (walletRestoringState) {
-                    WalletRestoringState.NONE -> BalanceState.None
-                    WalletRestoringState.INITIATING ->
-                        BalanceState.Available(
-                            totalBalance = walletSnapshot.totalBalance(),
-                            spendableBalance = walletSnapshot.spendableBalance()
+            .map { snapshot ->
+                when {
+                    // Show the loader only under these conditions:
+                    // - Available balance is currently zero
+                    // - Wallet has some ChangePending in progress
+                    // - And Total balance is non-zero
+                    (
+                        snapshot.spendableBalance().value == 0L &&
+                            snapshot.hasChangePending() &&
+                            snapshot.totalBalance().value > 0L
+                    ) -> {
+                        BalanceState.Loading(
+                            totalBalance = snapshot.totalBalance()
+                        )
+                    }
+                    else -> {
+                        BalanceState.Available(
+                            totalBalance = snapshot.totalBalance(),
+                            spendableBalance = snapshot.spendableBalance()
                         )
-                    WalletRestoringState.RESTORING, WalletRestoringState.SYNCING -> {
-                        if (walletSnapshot.spendableBalance().value == 0L &&
-                            walletSnapshot.totalBalance().value > 0L
-                        ) {
-                            BalanceState.Loading(
-                                totalBalance = walletSnapshot.totalBalance()
-                            )
-                        } else {
-                            BalanceState.Available(
-                                totalBalance = walletSnapshot.totalBalance(),
-                                spendableBalance = walletSnapshot.spendableBalance()
-                            )
-                        }
                     }
                 }
             }.stateIn(

ui-lib/src/main/java/co/electriccoin/zcash/ui/screen/balances/view/BalancesView.kt

@@ -57,6 +57,8 @@ import co.electriccoin.zcash.ui.common.compose.SynchronizationStatus
 import co.electriccoin.zcash.ui.common.model.WalletRestoringState
 import co.electriccoin.zcash.ui.common.model.WalletSnapshot
 import co.electriccoin.zcash.ui.common.model.changePendingBalance
+import co.electriccoin.zcash.ui.common.model.hasChangePending
+import co.electriccoin.zcash.ui.common.model.hasValuePending
 import co.electriccoin.zcash.ui.common.model.spendableBalance
 import co.electriccoin.zcash.ui.common.model.valuePendingBalance
 import co.electriccoin.zcash.ui.common.test.CommonTag
@@ -569,8 +571,6 @@ fun ChangePendingRow(walletSnapshot: WalletSnapshot) {
         )
 
         Row(verticalAlignment = Alignment.CenterVertically) {
-            val changePendingHasValue = walletSnapshot.changePendingBalance().value > 0L
-
             StyledBalance(
                 balanceString = walletSnapshot.changePendingBalance().toZecString(),
                 textStyles =
@@ -584,7 +584,7 @@ fun ChangePendingRow(walletSnapshot: WalletSnapshot) {
             Spacer(modifier = Modifier.width(12.dp))
 
             Box(Modifier.width(ZcashTheme.dimens.circularSmallProgressWidth)) {
-                if (changePendingHasValue) {
+                if (walletSnapshot.hasChangePending()) {
                     CircularSmallProgressIndicator()
                 }
             }
@@ -605,8 +605,6 @@ fun PendingTransactionsRow(walletSnapshot: WalletSnapshot) {
         )
 
         Row(verticalAlignment = Alignment.CenterVertically) {
-            val valuePendingHasValue = walletSnapshot.valuePendingBalance().value > 0L
-
             StyledBalance(
                 balanceString = walletSnapshot.valuePendingBalance().toZecString(),
                 textStyles =
@@ -620,7 +618,7 @@ fun PendingTransactionsRow(walletSnapshot: WalletSnapshot) {
             Spacer(modifier = Modifier.width(12.dp))
 
             Box(Modifier.width(ZcashTheme.dimens.circularSmallProgressWidth)) {
-                if (valuePendingHasValue) {
+                if (walletSnapshot.hasValuePending()) {
                     CircularSmallProgressIndicator()
                 }
             }