Add Undo snackbar on Bookmark removal

Change-Id: I1fefd6e72378e26ae35b66e032529a116cff9a79

feature/bookmarks/build.gradle.kts

@@ -14,8 +14,6 @@
  * limitations under the License.
  */
 
-import com.android.build.api.dsl.ManagedVirtualDevice
-
 plugins {
     id("nowinandroid.android.feature")
     id("nowinandroid.android.library.compose")
@@ -28,4 +26,4 @@ android {
 
 dependencies {
     implementation(libs.androidx.compose.material3.windowSizeClass)
-}
+}

feature/bookmarks/src/main/java/com/google/samples/apps/nowinandroid/feature/bookmarks/BookmarksScreen.kt

@@ -19,6 +19,7 @@ package com.google.samples.apps.nowinandroid.feature.bookmarks
 import androidx.annotation.VisibleForTesting
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Spacer
@@ -34,13 +35,23 @@ import androidx.compose.foundation.lazy.grid.GridCells.Adaptive
 import androidx.compose.foundation.lazy.grid.GridItemSpan
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.foundation.lazy.grid.rememberLazyGridState
+import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarDuration.Short
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.SnackbarResult.ActionPerformed
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.ColorFilter
+import androidx.compose.ui.platform.LocalLifecycleOwner
 import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
@@ -50,6 +61,8 @@ import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleEventObserver
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.google.samples.apps.nowinandroid.core.designsystem.component.NiaLoadingWheel
 import com.google.samples.apps.nowinandroid.core.designsystem.theme.LocalTintTheme
@@ -76,12 +89,16 @@ internal fun BookmarksRoute(
         onNewsResourceViewed = { viewModel.setNewsResourceViewed(it, true) },
         onTopicClick = onTopicClick,
         modifier = modifier,
+        shouldDisplayUndoBookmark = viewModel.shouldDisplayUndoBookmark,
+        undoBookmarkRemoval = viewModel::undoBookmarkRemoval,
+        clearUndoState = viewModel::clearUndoState,
     )
 }
 
 /**
  * Displays the user's bookmarked articles. Includes support for loading and empty states.
  */
+@OptIn(ExperimentalMaterial3Api::class)
 @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
 @Composable
 internal fun BookmarksScreen(
@@ -90,13 +107,51 @@ internal fun BookmarksScreen(
     onNewsResourceViewed: (String) -> Unit,
     onTopicClick: (String) -> Unit,
     modifier: Modifier = Modifier,
+    shouldDisplayUndoBookmark: Boolean = false,
+    undoBookmarkRemoval: () -> Unit = {},
+    clearUndoState: () -> Unit = {},
 ) {
-    when (feedState) {
-        Loading -> LoadingState(modifier)
-        is Success -> if (feedState.feed.isNotEmpty()) {
-            BookmarksGrid(feedState, removeFromBookmarks, onNewsResourceViewed, onTopicClick, modifier)
-        } else {
-            EmptyState(modifier)
+    val bookmarkRemovedMessage = stringResource(id = R.string.bookmark_removed)
+    val undoText = stringResource(id = R.string.undo)
+    val snackbarHostState = remember { SnackbarHostState() }
+
+    LaunchedEffect(shouldDisplayUndoBookmark) {
+        if (shouldDisplayUndoBookmark) {
+            val snackBarResult = snackbarHostState.showSnackbar(
+                message = bookmarkRemovedMessage,
+                actionLabel = undoText,
+                duration = Short,
+            )
+            when (snackBarResult) {
+                ActionPerformed -> { undoBookmarkRemoval() }
+                else -> { clearUndoState() }
+            }
+        }
+    }
+
+    val lifecycleOwner = LocalLifecycleOwner.current
+    DisposableEffect(lifecycleOwner) {
+        val observer = LifecycleEventObserver { _, event ->
+            if (event == Lifecycle.Event.ON_STOP) {
+                clearUndoState()
+            }
+        }
+        lifecycleOwner.lifecycle.addObserver(observer)
+        onDispose { lifecycleOwner.lifecycle.removeObserver(observer) }
+    }
+
+    Scaffold(snackbarHost = { SnackbarHost(hostState = snackbarHostState) }) {
+        Box(
+            modifier = Modifier.padding(it).fillMaxSize(),
+        ) {
+            when (feedState) {
+                Loading -> LoadingState(modifier)
+                is Success -> if (feedState.feed.isNotEmpty()) {
+                    BookmarksGrid(feedState, removeFromBookmarks, onNewsResourceViewed, onTopicClick, modifier)
+                } else {
+                    EmptyState(modifier)
+                }
+            }
         }
     }
     TrackScreenViewEvent(screenName = "Saved")

feature/bookmarks/src/main/java/com/google/samples/apps/nowinandroid/feature/bookmarks/BookmarksViewModel.kt

@@ -16,6 +16,9 @@
 
 package com.google.samples.apps.nowinandroid.feature.bookmarks
 
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.google.samples.apps.nowinandroid.core.data.repository.UserDataRepository
@@ -38,6 +41,9 @@ class BookmarksViewModel @Inject constructor(
     userNewsResourceRepository: UserNewsResourceRepository,
 ) : ViewModel() {
 
+    var shouldDisplayUndoBookmark by mutableStateOf(false)
+    private var lastRemovedBookmarkId: String? = null
+
     val feedUiState: StateFlow<NewsFeedUiState> =
         userNewsResourceRepository.observeAllBookmarked()
             .map<List<UserNewsResource>, NewsFeedUiState>(NewsFeedUiState::Success)
@@ -50,6 +56,8 @@ class BookmarksViewModel @Inject constructor(
 
     fun removeFromSavedResources(newsResourceId: String) {
         viewModelScope.launch {
+            shouldDisplayUndoBookmark = true
+            lastRemovedBookmarkId = newsResourceId
             userDataRepository.updateNewsResourceBookmark(newsResourceId, false)
         }
     }
@@ -59,4 +67,18 @@ class BookmarksViewModel @Inject constructor(
             userDataRepository.setNewsResourceViewed(newsResourceId, viewed)
         }
     }
+
+    fun undoBookmarkRemoval() {
+        viewModelScope.launch {
+            lastRemovedBookmarkId?.let {
+                userDataRepository.updateNewsResourceBookmark(it, true)
+            }
+        }
+        clearUndoState()
+    }
+
+    fun clearUndoState() {
+        shouldDisplayUndoBookmark = false
+        lastRemovedBookmarkId = null
+    }
 }

feature/bookmarks/src/main/res/values/strings.xml

@@ -22,4 +22,6 @@
     <string name="top_app_bar_action_menu">Menu</string>
     <string name="bookmarks_empty_error">No saved updates</string>
     <string name="bookmarks_empty_description">Updates you save will be stored here\nto read later</string>
-</resources>
+    <string name="bookmark_removed">Bookmark removed</string>
+    <string name="undo">UNDO</string>
+</resources>