[BWA-99] fix: Show next code only in last 10 seconds; fix flow caching bug

- Cache getLocalVerificationCodesFlow() as a class property so
  handleShowNextTotpCodeReceive reads from the already-subscribed
  flow instead of a new unsubscribed instance that always returns
  DataState.Loading (which caused the next code to never appear)
- Add 10-second threshold: next code is only shown when timeLeftSeconds
  is at or below 10 seconds remaining in the current period
- Update tests for the threshold (timeLeftSeconds = 5 / 10 / 11 cases)

authenticator/src/main/kotlin/com/bitwarden/authenticator/ui/authenticator/feature/itemlisting/ItemListingViewModel.kt

@@ -70,6 +70,10 @@ class ItemListingViewModel @Inject constructor(
     ),
 ) {
 
+    // Cached once so that handleShowNextTotpCodeReceive can read `.value` from the
+    // already-subscribed flow rather than creating a new unsubscribed instance.
+    private val localCodesFlow = authenticatorRepository.getLocalVerificationCodesFlow()
+
     init {
         settingsRepository
             .authenticatorAlertThresholdSecondsFlow
@@ -84,7 +88,7 @@ class ItemListingViewModel @Inject constructor(
             .launchIn(viewModelScope)
 
         combine(
-            flow = authenticatorRepository.getLocalVerificationCodesFlow(),
+            flow = localCodesFlow,
             flow2 = authenticatorRepository.sharedCodesStateFlow,
             ItemListingAction.Internal::AuthCodesUpdated,
         )
@@ -467,10 +471,10 @@ class ItemListingViewModel @Inject constructor(
         mutableStateFlow.update {
             it.copy(showNextTotpCode = action.showNextTotpCode)
         }
-        // Re-derive the displayed list so that the next code is shown/hidden immediately
-        // when the user toggles the setting.
+        // Immediately re-derive the displayed list using the cached subscribed flow so that
+        // next-code visibility changes take effect without waiting for the next 1-second tick.
         val codesUpdate = ItemListingAction.Internal.AuthCodesUpdated(
-            localCodes = authenticatorRepository.getLocalVerificationCodesFlow().value,
+            localCodes = localCodesFlow.value,
             sharedCodesState = authenticatorRepository.sharedCodesStateFlow.value,
         )
         handleAuthenticatorDataReceive(codesUpdate)

authenticator/src/main/kotlin/com/bitwarden/authenticator/ui/authenticator/feature/util/VerificationCodeItemExtensions.kt

@@ -5,12 +5,15 @@ import com.bitwarden.authenticator.data.authenticator.repository.model.Authentic
 import com.bitwarden.authenticator.data.authenticator.repository.model.SharedVerificationCodesState
 import com.bitwarden.authenticator.ui.platform.components.listitem.model.VerificationCodeDisplayItem
 
+private const val NEXT_CODE_SHOW_THRESHOLD_SECONDS = 10
+
 /**
  * Converts [VerificationCodeItem] to a [VerificationCodeDisplayItem].
  *
  * @param showNextCode When `true`, the upcoming code is mapped to
- *  [VerificationCodeDisplayItem.nextAuthCode]. When `false`, [VerificationCodeDisplayItem.nextAuthCode]
- *  is always `null`.
+ *  [VerificationCodeDisplayItem.nextAuthCode] for items within the last
+ *  [NEXT_CODE_SHOW_THRESHOLD_SECONDS] seconds of their validity period. When `false`,
+ *  [VerificationCodeDisplayItem.nextAuthCode] is always `null`.
  */
 fun VerificationCodeItem.toDisplayItem(
     alertThresholdSeconds: Int,
@@ -30,7 +33,11 @@ fun VerificationCodeItem.toDisplayItem(
     periodSeconds = periodSeconds,
     alertThresholdSeconds = alertThresholdSeconds,
     authCode = code,
-    nextAuthCode = if (showNextCode) nextCode else null,
+    nextAuthCode = if (showNextCode && timeLeftSeconds <= NEXT_CODE_SHOW_THRESHOLD_SECONDS) {
+        nextCode
+    } else {
+        null
+    },
     showOverflow = showOverflow,
     favorite = (source as? AuthenticatorItem.Source.Local)?.isFavorite ?: false,
     showMoveToBitwarden = when (source) {

authenticator/src/test/kotlin/com/bitwarden/authenticator/ui/authenticator/feature/itemlisting/ItemListingViewModelTest.kt

@@ -582,7 +582,7 @@ class ItemListingViewModelTest : BaseViewModelTest() {
         val verificationItem = VerificationCodeItem(
             code = "123456",
             periodSeconds = 60,
-            timeLeftSeconds = 430,
+            timeLeftSeconds = 5,
             issueTime = 35L,
             id = "1",
             issuer = "issuer",

authenticator/src/test/kotlin/com/bitwarden/authenticator/ui/authenticator/feature/util/VerificationCodeItemExtensionsTest.kt

@@ -146,8 +146,9 @@ class VerificationCodeItemExtensionsTest {
     }
 
     @Test
-    fun `toDisplayItem should set nextAuthCode to nextCode when showNextCode is true`() {
-        val item = createMockVerificationCodeItem(number = 1, nextCode = "654321")
+    @Suppress("MaxLineLength")
+    fun `toDisplayItem should set nextAuthCode when showNextCode is true and timeLeftSeconds is within threshold`() {
+        val item = createMockVerificationCodeItem(number = 1, nextCode = "654321", timeLeftSeconds = 5)
         val result = item.toDisplayItem(
             alertThresholdSeconds = 7,
             sharedVerificationCodesState = SharedVerificationCodesState.Error,
@@ -157,9 +158,39 @@ class VerificationCodeItemExtensionsTest {
         assertEquals("654321", result.nextAuthCode)
     }
 
+    @Test
+    @Suppress("MaxLineLength")
+    fun `toDisplayItem should set nextAuthCode when showNextCode is true and timeLeftSeconds equals threshold`() {
+        val item = createMockVerificationCodeItem(number = 1, nextCode = "654321", timeLeftSeconds = 10)
+        val result = item.toDisplayItem(
+            alertThresholdSeconds = 7,
+            sharedVerificationCodesState = SharedVerificationCodesState.Error,
+            showOverflow = true,
+            showNextCode = true,
+        )
+        assertEquals("654321", result.nextAuthCode)
+    }
+
+    @Test
+    @Suppress("MaxLineLength")
+    fun `toDisplayItem should set nextAuthCode to null when showNextCode is true but timeLeftSeconds exceeds threshold`() {
+        val item = createMockVerificationCodeItem(number = 1, nextCode = "654321", timeLeftSeconds = 11)
+        val result = item.toDisplayItem(
+            alertThresholdSeconds = 7,
+            sharedVerificationCodesState = SharedVerificationCodesState.Error,
+            showOverflow = true,
+            showNextCode = true,
+        )
+        assertEquals(null, result.nextAuthCode)
+    }
+
     @Test
     fun `toDisplayItem should set nextAuthCode to null when showNextCode is false`() {
-        val item = createMockVerificationCodeItem(number = 1, nextCode = "654321")
+        val item = createMockVerificationCodeItem(
+            number = 1,
+            nextCode = "654321",
+            timeLeftSeconds = 5,
+        )
         val result = item.toDisplayItem(
             alertThresholdSeconds = 7,
             sharedVerificationCodesState = SharedVerificationCodesState.Error,
@@ -172,7 +203,7 @@ class VerificationCodeItemExtensionsTest {
     @Test
     @Suppress("MaxLineLength")
     fun `toDisplayItem should set nextAuthCode to null when showNextCode true but nextCode is null`() {
-        val item = createMockVerificationCodeItem(number = 1, nextCode = null)
+        val item = createMockVerificationCodeItem(number = 1, nextCode = null, timeLeftSeconds = 5)
         val result = item.toDisplayItem(
             alertThresholdSeconds = 7,
             sharedVerificationCodesState = SharedVerificationCodesState.Error,