feat(messages): tag-filtered feed, sharing the feed implementation (#29)

app/src/main/AndroidManifest.xml

@@ -29,6 +29,13 @@
                 destinations (shared list/document tokens, password reset, email
                 verification, and the confirm/undo halves of an email change).
                 autoVerify enables Android App Links verification.
+
+                The site root is registered for the tag feed: the web links every
+                tag on a message card to "/?tag=<tag>" (there is no /tag/<tag>
+                path — it 404s), and an intent filter cannot match on a query
+                string. So "/" is the narrowest filter that can catch a tag link.
+                A root link with no tag simply opens the app's normal start
+                destination, which shows the same feed the homepage does.
             -->
             <intent-filter android:autoVerify="true">
                 <action android:name="android.intent.action.VIEW" />
@@ -37,6 +44,7 @@
                 <data android:scheme="https" android:host="interlinedlist.com" />
                 <data android:pathPrefix="/lists/shared/" />
                 <data android:pathPrefix="/documents/shared/" />
+                <data android:path="/" />
                 <data android:path="/reset-password" />
                 <data android:path="/verify-email" />
                 <data android:path="/verify-email-change" />
@@ -50,6 +58,7 @@
                 <category android:name="android.intent.category.BROWSABLE" />
                 <data android:scheme="interlinedlist" android:host="lists" />
                 <data android:scheme="interlinedlist" android:host="documents" />
+                <data android:scheme="interlinedlist" android:host="tag" />
                 <data android:scheme="interlinedlist" android:host="reset-password" />
                 <data android:scheme="interlinedlist" android:host="verify-email" />
                 <data android:scheme="interlinedlist" android:host="verify-email-change" />

app/src/main/java/com/interlinedlist/android/MainActivity.kt

@@ -13,6 +13,7 @@ import com.interlinedlist.android.core.datastore.ThemeMode
 import com.interlinedlist.android.core.datastore.ThemeSettingsStore
 import com.interlinedlist.android.core.designsystem.theme.InterlinedListTheme
 import com.interlinedlist.android.feature.auth.nav.AuthRoutes
+import com.interlinedlist.android.feature.messages.navigation.MessagesDestinations
 import com.interlinedlist.android.navigation.InterlinedListNavHost
 import com.interlinedlist.android.navigation.NotificationLaunch
 import dagger.hilt.android.AndroidEntryPoint
@@ -40,6 +41,10 @@ class MainActivity : ComponentActivity() {
         // the VIEW intent's data. Both endpoints behind it are unauthenticated, so the
         // route resolves regardless of whether a session exists.
         val emailChangeRoute = AuthRoutes.routeForEmailChangeLink(intent?.dataString)
+        // A tapped tag link (`https://interlinedlist.com/?tag=…`, the URL the web's
+        // own tag chips point at) resolves to the tag-filtered feed. Resolved here
+        // rather than by implicit nav matching so the rule is unit-testable.
+        val tagFeedRoute = MessagesDestinations.routeForTagLink(intent?.dataString)
         enableEdgeToEdge()
         setContent {
             val themeMode by themeSettingsStore.themeMode.collectAsStateWithLifecycle()
@@ -53,6 +58,7 @@ class MainActivity : ComponentActivity() {
                     startLoggedIn = startLoggedIn,
                     notificationRoute = notificationRoute,
                     emailChangeRoute = emailChangeRoute,
+                    tagFeedRoute = tagFeedRoute,
                 )
             }
         }

app/src/main/java/com/interlinedlist/android/navigation/InterlinedListNavHost.kt

@@ -59,6 +59,7 @@ import com.interlinedlist.android.feature.lists.ui.share.ShareRoute
 import com.interlinedlist.android.feature.lists.ui.share.SharedListRoute
 import com.interlinedlist.android.feature.lists.ui.share.SharedWithMeRoute
 import com.interlinedlist.android.feature.lists.ui.watchers.WatchersRoute
+import com.interlinedlist.android.feature.messages.navigation.MessagesDestinations
 import com.interlinedlist.android.feature.messages.ui.detail.MessageDetailRoute
 import com.interlinedlist.android.feature.messages.ui.feed.MessagesRoute
 import com.interlinedlist.android.feature.messages.ui.scheduled.ScheduledMessagesRoute
@@ -193,6 +194,7 @@ fun InterlinedListNavHost(
     startLoggedIn: Boolean,
     notificationRoute: String? = null,
     emailChangeRoute: String? = null,
+    tagFeedRoute: String? = null,
 ) {
     val navController = rememberNavController()
     NavHost(
@@ -215,7 +217,8 @@ fun InterlinedListNavHost(
         composable(Routes.MAIN) {
             val context = LocalContext.current
             MainShell(
-                notificationRoute = notificationRoute,
+                // A launch is either a notification tap or a link tap, never both.
+                pendingRoute = notificationRoute ?: tagFeedRoute,
                 onLoggedOut = {
                     // Stop background sync/poll for the signed-out session. Cancellation
                     // must never crash the sign-out flow, so any failure is swallowed.
@@ -244,7 +247,7 @@ fun InterlinedListNavHost(
  */
 @Composable
 private fun MainShell(
-    notificationRoute: String? = null,
+    pendingRoute: String? = null,
     onLoggedOut: () -> Unit,
 ) {
     val tabNav = rememberNavController()
@@ -278,10 +281,11 @@ private fun MainShell(
     val pushRegistration: PushRegistrationViewModel = hiltViewModel()
     LaunchedEffect(Unit) { pushRegistration.runForSession() }
 
-    // Route straight to a tapped notification's destination once, when present.
-    val pendingRoute by rememberUpdatedState(notificationRoute)
+    // Route straight to the launch's destination once, when present: a tapped
+    // notification, or a tapped link (a tag feed) resolved in MainActivity.
+    val launchRoute by rememberUpdatedState(pendingRoute)
     LaunchedEffect(Unit) {
-        pendingRoute?.let { route ->
+        launchRoute?.let { route ->
             runCatching { tabNav.navigate(route) }
         }
     }
@@ -321,6 +325,22 @@ private fun MainShell(
                 MessagesRoute(
                     onOpenMessage = { id -> tabNav.navigate(Routes.messageDetail(id)) },
                     onOpenScheduled = { tabNav.navigate(Routes.MESSAGES_SCHEDULED) },
+                    onOpenTag = { tag -> tabNav.navigate(MessagesDestinations.tagFeedRoute(tag)) },
+                )
+            }
+            // The same feed screen, filtered to one tag. The tag arrives as a nav
+            // argument, so paging and the view switcher are shared, not forked.
+            composable(
+                MessagesDestinations.TAG_FEED,
+                arguments = listOf(
+                    navArgument(MessagesDestinations.ARG_TAG) { type = NavType.StringType },
+                ),
+            ) {
+                MessagesRoute(
+                    onOpenMessage = { id -> tabNav.navigate(Routes.messageDetail(id)) },
+                    onOpenScheduled = {},
+                    onOpenTag = { tag -> tabNav.navigate(MessagesDestinations.tagFeedRoute(tag)) },
+                    onBack = { tabNav.popBackStack() },
                 )
             }
             composable(
@@ -330,6 +350,7 @@ private fun MainShell(
                 MessageDetailRoute(
                     onBack = { tabNav.popBackStack() },
                     onOpenMessage = { id -> tabNav.navigate(Routes.messageDetail(id)) },
+                    onOpenTag = { tag -> tabNav.navigate(MessagesDestinations.tagFeedRoute(tag)) },
                 )
             }
             composable(Routes.MESSAGES_SCHEDULED) {

feature/messages/src/androidTest/kotlin/com/interlinedlist/android/feature/messages/ui/feed/MessagesFeedScreenTest.kt

@@ -79,6 +79,8 @@ class MessagesFeedScreenTest {
         onPush: (Message) -> Unit = {},
         onQuote: (Message) -> Unit = {},
         onSelectTagSuggestion: (TagSuggestion) -> Unit = {},
+        onOpenTag: ((String) -> Unit)? = null,
+        onBack: () -> Unit = {},
     ) {
         composeRule.setContent {
             var state by mutableStateOf(initial)
@@ -137,6 +139,8 @@ class MessagesFeedScreenTest {
                         state = state.copy(isComposeOpen = true, quoteTarget = quoted)
                         onQuote(quoted)
                     },
+                    onOpenTag = onOpenTag,
+                    onBack = onBack,
                 )
             }
         }
@@ -593,6 +597,67 @@ class MessagesFeedScreenTest {
         composeRule.onNodeWithText(tag).assertIsDisplayed()
     }
 
+    @Test
+    fun tappingATag_opensThatTagsFeed() {
+        val opened = mutableListOf<String>()
+        setFeed(
+            MessagesFeedUiState(messages = listOf(message("1", "tagged post", tags = listOf("lists")))),
+            onOpenTag = { opened += it },
+        )
+
+        composeRule.onNodeWithTag(MessageCardTags.tagTag("lists")).performClick()
+
+        assertThat(opened).containsExactly("lists")
+    }
+
+    @Test
+    fun tappingATagWithSpacesAndPunctuation_passesItWhole() {
+        val tag = "life is short, o brave girl"
+        val opened = mutableListOf<String>()
+        setFeed(
+            MessagesFeedUiState(messages = listOf(message("1", "tagged", tags = listOf(tag)))),
+            onOpenTag = { opened += it },
+        )
+
+        composeRule.onNodeWithTag(MessageCardTags.tagTag(tag)).performClick()
+
+        // Exactly the tag the card carried: not trimmed, split or lowercased.
+        assertThat(opened).containsExactly(tag)
+    }
+
+    @Test
+    fun tags_areInert_whereTheHostWiresNoTagDestination() {
+        setFeed(MessagesFeedUiState(messages = listOf(message("1", "tagged", tags = listOf("lists")))))
+        composeRule.onNodeWithTag(MessageCardTags.tagTag("lists")).assertHasNoClickAction()
+    }
+
+    @Test
+    fun tagFeed_showsTheTagAndABackArrow_insteadOfTheComposerAndScheduled() {
+        val backs = mutableListOf<Unit>()
+        setFeed(
+            MessagesFeedUiState(
+                tag = "lists",
+                messages = listOf(message("1", "tagged", tags = listOf("lists"))),
+            ),
+            onBack = { backs += Unit },
+        )
+
+        composeRule.onNodeWithTag(MessagesFeedTags.TAG_TITLE).assertIsDisplayed()
+        // Composing here would post an untagged message into a feed it cannot join.
+        composeRule.onNodeWithTag(MessagesFeedTags.FAB).assertDoesNotExist()
+        composeRule.onNodeWithTag(MessagesFeedTags.SCHEDULED_ACTION).assertDoesNotExist()
+
+        composeRule.onNodeWithTag(MessagesFeedTags.BACK).performClick()
+        assertThat(backs).hasSize(1)
+    }
+
+    @Test
+    fun tagFeed_keepsTheViewPreferenceSwitcher() {
+        // The tag feed is a normal feed: the account's view preference still applies.
+        setFeed(MessagesFeedUiState(tag = "lists", messages = listOf(message("1", "tagged"))))
+        composeRule.onNodeWithTag(MessagesFeedTags.VIEW_PREFERENCES).assertIsDisplayed()
+    }
+
     @Test
     fun noTagRow_isShown_forAnUntaggedMessage() {
         setFeed(MessagesFeedUiState(messages = listOf(message("1", "plain"))))