Fix next after all read (#2041)

* Hold onto ref current feed for next page

Fixes a bug where the Unread feed would lose
context of the next filter since the current filter was
removed from the sidebar

* Skip emptied descendants when advancing feed

When the current sidebar item vanishes after mark-read, walk the
stale .next chain to find the first successor still present in the
rebuilt sidebar. Handles marking a folder read with expanded children.

Author: jocmp

app/src/main/java/com/capyreader/app/ui/articles/ArticleScreenViewModel.kt

@@ -195,9 +195,9 @@ class ArticleScreenViewModel(
         )
     }
 
-    private val _nextItem = MutableStateFlow<SidebarItem?>(null)
+    private val _sidebarItem = MutableStateFlow<SidebarItem?>(null)
 
-    private val nextItemListener: Flow<SidebarItem?> =
+    private val sidebarListener: Flow<SidebarItem?> =
         combine(
             listSwipeBottom,
             sidebar,
@@ -207,9 +207,38 @@ class ArticleScreenViewModel(
                 return@combine null
             }
 
-            sidebar.find { it.isSelected(filter) }?.next
+            val found = sidebar.find { it.isSelected(filter) }
+            if (found != null) return@combine found
+
+            val stale = _sidebarItem.value?.takeIf { it.isSelected(filter) }
+                ?: return@combine null
+
+            SidebarItem(
+                toFilter = stale.toFilter,
+                isSelected = stale.isSelected,
+                next = findFreshItem(stale, sidebar, filter.status),
+            )
         }
 
+    private fun findFreshItem(
+        stale: SidebarItem,
+        sidebar: List<SidebarItem>,
+        status: ArticleStatus,
+    ): SidebarItem? {
+        var search: SidebarItem? = stale.next
+
+        while (search != null) {
+            val searchFilter = search.toFilter(status)
+            val match = sidebar.find { it.isSelected(searchFilter) }
+            if (match != null) {
+                return match
+            }
+            search = search.next
+        }
+
+        return null
+    }
+
     val statusCount: Flow<Long> = filter.flatMapLatest { latestFilter ->
         account.countAllByStatus(countableStatus(latestFilter))
     }
@@ -240,17 +269,17 @@ class ArticleScreenViewModel(
     val searchState: Flow<SearchState>
         get() = _searchState
 
-    val nextFilter: Flow<SidebarItem?>
-        get() = _nextItem
+    val nextFilter: Flow<SidebarItem?> = _sidebarItem.map { it?.next }
 
     init {
         viewModelScope.launch {
-            nextItemListener.collect {
-                _nextItem.value = it
+            sidebarListener.collect {
+                _sidebarItem.value = it
             }
         }
 
-        val skipInitialRefresh = appPreferences.refreshInterval.get() == RefreshInterval.MANUALLY_ONLY
+        val skipInitialRefresh =
+            appPreferences.refreshInterval.get() == RefreshInterval.MANUALLY_ONLY
 
         if (skipInitialRefresh) {
             refreshInitialized = true
@@ -604,7 +633,7 @@ class ArticleScreenViewModel(
     }
 
     fun requestNextFeed() {
-        _nextItem.value?.let(::selectSidebarItem)
+        _sidebarItem.value?.next?.let(::selectSidebarItem)
     }
 
     private fun selectSidebarItem(item: SidebarItem) {
@@ -789,7 +818,7 @@ class ArticleScreenViewModel(
     private fun openNextFeedOnAllRead(
         onArticlesCleared: () -> Unit,
     ) {
-        val nextItem = _nextItem.value
+        val nextItem = _sidebarItem.value?.next
 
         if (nextItem != null) {
             selectSidebarItem(nextItem)

app/src/test/java/com/capyreader/app/ui/articles/ArticleScreenViewModelTest.kt

@@ -3,16 +3,16 @@ package com.capyreader.app.ui.articles
 import android.app.Application
 import app.cash.turbine.test
 import com.capyreader.app.notifications.NotificationHelper
-import com.capyreader.app.preferences.AfterReadAllBehavior
 import com.capyreader.app.preferences.AppPreferences
 import com.capyreader.app.preferences.ArticleListVerticalSwipe
 import com.capyreader.app.refresher.RefreshInterval
 import com.capyreader.app.ui.articles.feeds.AngleRefreshState
 import com.jocmp.capy.Account
 import com.jocmp.capy.ArticleFilter
+import com.jocmp.capy.ArticleStatus
+import com.jocmp.capy.Feed
+import com.jocmp.capy.Folder
 import com.jocmp.capy.accounts.Source
-import com.jocmp.capy.articles.SortOrder
-import com.jocmp.capy.preferences.Preference
 import io.mockk.coEvery
 import io.mockk.every
 import io.mockk.mockk
@@ -54,20 +54,20 @@ class ArticleScreenViewModelTest {
             every { feeds } returns flowOf(emptyList())
             every { taggedFeeds } returns flowOf(emptyList())
             every { savedSearches } returns flowOf(emptyList())
-            every { canSaveArticleExternally } returns mockPreference(false)
+            every { canSaveArticleExternally } returns mockk(relaxed = true) {
+                every { get() } returns false
+                every { stateIn(any()) } returns MutableStateFlow(false)
+                every { changes() } returns flowOf(false)
+            }
+            every { countAll(any()) } returns flowOf(emptyMap())
+            every { countAllBySavedSearch(any()) } returns flowOf(emptyMap())
             every { source } returns Source.LOCAL
             coEvery { refresh(any()) } returns Result.success(Unit)
         }
 
-        appPreferences = mockk(relaxed = true) {
-            every { filter } returns mockPreference(ArticleFilter.default())
-            every { refreshInterval } returns mockPreference(RefreshInterval.EVERY_TWO_HOURS)
-            every { enableStickyFullContent } returns mockPreference(false)
-            every { articleListOptions } returns mockk(relaxed = true) {
-                every { swipeBottom } returns mockPreference(ArticleListVerticalSwipe.DISABLED)
-                every { sortOrder } returns mockPreference(SortOrder.default)
-                every { afterReadAllBehavior } returns mockPreference(AfterReadAllBehavior.default)
-            }
+        appPreferences = AppPreferences(RuntimeEnvironment.getApplication()).also {
+            it.clearAll()
+            it.refreshInterval.set(RefreshInterval.EVERY_TWO_HOURS)
         }
 
         notificationHelper = mockk(relaxed = true)
@@ -92,7 +92,7 @@ class ArticleScreenViewModelTest {
 
     @Test
     fun `skips initial refresh when refresh interval is manual only`() = runTest {
-        every { appPreferences.refreshInterval } returns mockPreference(RefreshInterval.MANUALLY_ONLY)
+        appPreferences.refreshInterval.set(RefreshInterval.MANUALLY_ONLY)
 
         val viewModel = buildViewModel()
 
@@ -102,7 +102,7 @@ class ArticleScreenViewModelTest {
 
     @Test
     fun `refreshAll transitions from stopped, running, to settling`() = runTest {
-        every { appPreferences.refreshInterval } returns mockPreference(RefreshInterval.MANUALLY_ONLY)
+        appPreferences.refreshInterval.set(RefreshInterval.MANUALLY_ONLY)
 
         val viewModel = buildViewModel()
 
@@ -120,7 +120,7 @@ class ArticleScreenViewModelTest {
 
     @Test
     fun `refreshAll guards against double calls while running`() = runTest {
-        every { appPreferences.refreshInterval } returns mockPreference(RefreshInterval.MANUALLY_ONLY)
+        appPreferences.refreshInterval.set(RefreshInterval.MANUALLY_ONLY)
 
         val viewModel = buildViewModel()
 
@@ -138,6 +138,82 @@ class ArticleScreenViewModelTest {
         }
     }
 
+    @Test
+    fun `requestNextFeed opens next feed after current feed's unread count drops to zero`() = runTest {
+        val initialFilter = ArticleFilter.Feeds(
+            feedID = "1",
+            folderTitle = null,
+            feedStatus = ArticleStatus.UNREAD
+        )
+        appPreferences.filter.set(initialFilter)
+        appPreferences.articleListOptions.swipeBottom.set(ArticleListVerticalSwipe.NEXT_FEED)
+
+        val feedA = Feed(id = "1", subscriptionID = "1", title = "A", feedURL = "a", count = 3)
+        val feedB = Feed(id = "2", subscriptionID = "2", title = "B", feedURL = "b", count = 3)
+
+        val feeds = MutableStateFlow(listOf(feedA, feedB))
+        val counts = MutableStateFlow<Map<String, Long>>(mapOf("1" to 3, "2" to 3))
+
+        every { account.feeds } returns feeds
+        every { account.countAll(any()) } returns counts
+
+        val viewModel = buildViewModel()
+        advanceUntilIdle()
+
+        counts.value = mapOf("1" to 0, "2" to 3)
+        advanceUntilIdle()
+
+        viewModel.requestNextFeed()
+        advanceUntilIdle()
+
+        val expectedNext = ArticleFilter.Feeds(
+            feedID = "2",
+            folderTitle = null,
+            feedStatus = ArticleStatus.UNREAD
+        )
+        assertEquals(expectedNext, appPreferences.filter.get())
+    }
+
+    @Test
+    fun `requestNextFeed skips empty children when current folder is marked read`() = runTest {
+        val initialFilter = ArticleFilter.Folders(
+            folderTitle = "X",
+            folderStatus = ArticleStatus.UNREAD,
+        )
+        appPreferences.filter.set(initialFilter)
+        appPreferences.articleListOptions.swipeBottom.set(ArticleListVerticalSwipe.NEXT_FEED)
+
+        val x1 = Feed(id = "x1", subscriptionID = "x1", title = "X1", feedURL = "x1", folderName = "X")
+        val x2 = Feed(id = "x2", subscriptionID = "x2", title = "X2", feedURL = "x2", folderName = "X")
+        val y1 = Feed(id = "y1", subscriptionID = "y1", title = "Y1", feedURL = "y1", folderName = "Y")
+
+        val folderX = Folder(title = "X", feeds = listOf(x1, x2), expanded = true)
+        val folderY = Folder(title = "Y", feeds = listOf(y1), expanded = true)
+
+        val folders = MutableStateFlow(listOf(folderX, folderY))
+        val counts = MutableStateFlow<Map<String, Long>>(
+            mapOf("x1" to 2L, "x2" to 2L, "y1" to 3L)
+        )
+
+        every { account.folders } returns folders
+        every { account.feeds } returns flowOf(emptyList())
+        every { account.countAll(any()) } returns counts
+
+        val viewModel = buildViewModel()
+        advanceUntilIdle()
+
+        counts.value = mapOf("x1" to 0L, "x2" to 0L, "y1" to 3L)
+        advanceUntilIdle()
+
+        viewModel.requestNextFeed()
+        advanceUntilIdle()
+
+        assertEquals(
+            ArticleFilter.Folders(folderTitle = "Y", folderStatus = ArticleStatus.UNREAD),
+            appPreferences.filter.get()
+        )
+    }
+
     private fun buildViewModel(): ArticleScreenViewModel {
         val application = RuntimeEnvironment.getApplication() as Application
 
@@ -149,12 +225,4 @@ class ArticleScreenViewModelTest {
             ioDispatcher = testDispatcher,
         )
     }
-
-    private inline fun <reified T> mockPreference(value: T): Preference<T> {
-        return mockk {
-            every { get() } returns value
-            every { stateIn(any()) } returns MutableStateFlow(value)
-            every { changes() } returns flowOf(value)
-        }
-    }
 }