[#663] Shield Funds button is enabled when there are no funds to shield (#665)

- This adds new logic for disabling the shield funds button and tests that
check that the state is consistent with the intended behaviour.
- handling button opacity is left for another PR
- one more condition to disable shield button

secant/Features/BalanceBreakdown/BalanceBreakdownStore.swift

@@ -26,6 +26,14 @@ struct BalanceBreakdownReducer: ReducerProtocol {
         var totalBalance: Zatoshi {
             shieldedBalance.data.total + transparentBalance.data.total
         }
+
+        var isShieldableBalanceAvailable: Bool {
+            transparentBalance.data.verified.amount >= autoShieldingThreshold.amount
+        }
+
+        var isShieldingButtonDisabled: Bool {
+            shieldingFunds || !isShieldableBalanceAvailable
+        }
     }
 
     enum Action: Equatable, BindableAction {

secant/Features/BalanceBreakdown/BalanceBreakdownView.swift

@@ -95,7 +95,7 @@ extension BalanceBreakdownView {
         )
         .activeButtonStyle
         .padding(.top, 30)
-        .disable(when: viewStore.shieldingFunds, dimmingOpacity: 0.5)
+        .disable(when: !viewStore.isShieldableBalanceAvailable || viewStore.shieldingFunds, dimmingOpacity: 0.5)
     }
 }
 

secantTests/BalanceBreakdownTests/BalanceBreakdownTests.swift

@@ -86,4 +86,59 @@ class BalanceBreakdownTests: XCTestCase {
         // the .onDisappear action cancels the observer of the synchronizer status change.
         await store.send(.onDisappear)
     }
+
+    @MainActor func testShieldFundsButtonDisabledWhenNoShieldableFunds() async throws {
+        let store = TestStore(
+            initialState: .placeholder,
+            reducer: BalanceBreakdownReducer()
+        )
+
+        XCTAssertFalse(store.state.shieldingFunds)
+        XCTAssertFalse(store.state.isShieldableBalanceAvailable)
+        XCTAssertTrue(store.state.isShieldingButtonDisabled)
+    }
+
+    @MainActor func testShieldFundsButtonEnabledWhenShieldableFundsAvailable() async throws {
+        let store = TestStore(
+            initialState: BalanceBreakdownReducer.State(
+                autoShieldingThreshold: Zatoshi(1_000_000),
+                latestBlock: L10n.General.unknown,
+                shieldedBalance: Balance.zero,
+                shieldingFunds: false,
+                transparentBalance: Balance(
+                    WalletBalance(
+                        verified: 1_000_000,
+                        total: 1_000_000
+                    )
+                )
+            ),
+            reducer: BalanceBreakdownReducer()
+        )
+
+        XCTAssertFalse(store.state.shieldingFunds)
+        XCTAssertTrue(store.state.isShieldableBalanceAvailable)
+        XCTAssertFalse(store.state.isShieldingButtonDisabled)
+    }
+
+    @MainActor func testShieldFundsButtonDisabledWhenShieldableFundsAvailableAndShielding() async throws {
+        let store = TestStore(
+            initialState: BalanceBreakdownReducer.State(
+                autoShieldingThreshold: Zatoshi(1_000_000),
+                latestBlock: L10n.General.unknown,
+                shieldedBalance: Balance.zero,
+                shieldingFunds: true,
+                transparentBalance: Balance(
+                    WalletBalance(
+                        verified: 1_000_000,
+                        total: 1_000_000
+                    )
+                )
+            ),
+            reducer: BalanceBreakdownReducer()
+        )
+
+        XCTAssertTrue(store.state.shieldingFunds)
+        XCTAssertTrue(store.state.isShieldableBalanceAvailable)
+        XCTAssertTrue(store.state.isShieldingButtonDisabled)
+    }
 }