Enable Undo removing favorite post

Author: paulcoding810

app/src/main/java/com/paulcoding/hviewer/ui/favorite/FavoritePage.kt

@@ -6,18 +6,25 @@ import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarDuration
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.SnackbarResult
 import androidx.compose.material3.Text
 import androidx.compose.material3.TopAppBar
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Modifier
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.paulcoding.hviewer.model.PostItem
 import com.paulcoding.hviewer.ui.component.HBackIcon
 import com.paulcoding.hviewer.ui.component.HEmpty
 import com.paulcoding.hviewer.ui.page.AppViewModel
 import com.paulcoding.hviewer.ui.page.posts.PostCard
+import kotlinx.coroutines.launch
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -27,19 +34,42 @@ fun FavoritePage(
     goBack: () -> Boolean
 ) {
     val viewModel: AppViewModel = viewModel()
+    val snackbarHostState = remember { SnackbarHostState() }
+    val scope = rememberCoroutineScope()
     val favoritePosts by viewModel.favoritePosts.collectAsState(initial = emptyList())
 
+    fun onDelete(post: PostItem) {
+        appViewModel.deleteFavorite(post)
+
+        scope.launch {
+            val result = snackbarHostState.showSnackbar(
+                "${post.name} removed from favorite",
+                "Undo",
+                duration = SnackbarDuration.Short
+            )
+            when (result) {
+                SnackbarResult.ActionPerformed -> {
+                    appViewModel.addFavorite(post, true)
+                }
+
+                SnackbarResult.Dismissed -> {
+                }
+            }
+        }
+    }
+
     Scaffold(
         modifier = Modifier.fillMaxSize(),
+        snackbarHost = { SnackbarHost(snackbarHostState) },
         topBar = {
             TopAppBar(title = { Text("Favorite") }, navigationIcon = {
                 HBackIcon { goBack() }
             })
         }) { paddings ->
         LazyColumn(modifier = Modifier.padding(paddings)) {
-            items(items = favoritePosts.reversed(), key = { it.url }) { item ->
-                FavoriteItem(item, navToImages = { navToImages(it) }, deleteFavorite = {
-                    appViewModel.deleteFavorite(it)
+            items(items = favoritePosts, key = { it.url }) { item ->
+                FavoriteItem(item, navToImages = { navToImages(item) }, deleteFavorite = {
+                    onDelete(item)
                 })
             }
             if (favoritePosts.isEmpty())
@@ -52,12 +82,12 @@ fun FavoritePage(
 @Composable
 fun FavoriteItem(
     post: PostItem,
-    navToImages: (PostItem) -> Unit,
-    deleteFavorite: (PostItem) -> Unit
+    navToImages: () -> Unit,
+    deleteFavorite: () -> Unit
 ) {
     PostCard(post, isFavorite = true, setFavorite = {
-        deleteFavorite(post)
+        deleteFavorite()
     }) {
-        navToImages(post)
+        navToImages()
     }
 }

app/src/main/java/com/paulcoding/hviewer/ui/page/AppViewModel.kt

@@ -29,10 +29,13 @@ class AppViewModel : ViewModel() {
         val site: Pair<String, SiteConfig> = "" to SiteConfig(),
     )
 
-    fun addFavorite(postItem: PostItem) {
+    fun addFavorite(postItem: PostItem, reAdded: Boolean = false) {
         viewModelScope.launch {
-            val postWithPage = postItem.copy(site = _stateFlow.value.site.first)
-            DatabaseProvider.getInstance().favoritePostDao().insert(postWithPage)
+            val item = if (reAdded) postItem else postItem.copy(
+                site = _stateFlow.value.site.first,
+                createdAt = System.currentTimeMillis()
+            )
+            DatabaseProvider.getInstance().favoritePostDao().insert(item)
         }
     }