refactor(android): move post save state logic to a Paging transform

Fixes #349

android/src/main/kotlin/dev/msfjarvis/claw/android/ui/LobstersApp.kt

@@ -179,7 +179,6 @@ fun LobstersApp(
           NetworkPosts(
             lazyPagingItems = hottestPosts,
             listState = hottestListState,
-            isPostSaved = viewModel::isPostSaved,
             postActions = postActions,
           )
         }
@@ -190,7 +189,6 @@ fun LobstersApp(
           NetworkPosts(
             lazyPagingItems = newestPosts,
             listState = newestListState,
-            isPostSaved = viewModel::isPostSaved,
             postActions = postActions,
           )
         }

android/src/main/kotlin/dev/msfjarvis/claw/android/ui/lists/DatabasePosts.kt

@@ -13,6 +13,7 @@ import androidx.compose.foundation.lazy.items
 import androidx.compose.material3.Divider
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
+import dev.msfjarvis.claw.common.posts.LobstersCard
 import dev.msfjarvis.claw.common.posts.PostActions
 import dev.msfjarvis.claw.common.ui.decorations.MonthHeader
 import dev.msfjarvis.claw.database.local.SavedPost
@@ -33,9 +34,9 @@ fun DatabasePosts(
     items.forEach { (month, posts) ->
       stickyHeader { MonthHeader(month = month) }
       items(posts) { item ->
-        ListItem(
-          item = item,
-          isSaved = { true },
+        LobstersCard(
+          post = item,
+          isSaved = true,
           postActions = postActions,
         )
 

android/src/main/kotlin/dev/msfjarvis/claw/android/ui/lists/ListItem.kt

@@ -1,31 +0,0 @@
-/*
- * Copyright © 2021-2022 Harsh Shandilya.
- * Use of this source code is governed by an MIT-style
- * license that can be found in the LICENSE file or at
- * https://opensource.org/licenses/MIT.
- */
-package dev.msfjarvis.claw.android.ui.lists
-
-import androidx.compose.runtime.Composable
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.produceState
-import androidx.compose.ui.Modifier
-import dev.msfjarvis.claw.common.posts.LobstersCard
-import dev.msfjarvis.claw.common.posts.PostActions
-import dev.msfjarvis.claw.database.local.SavedPost
-
-@Composable
-fun ListItem(
-  item: SavedPost,
-  isSaved: suspend (SavedPost) -> Boolean,
-  postActions: PostActions,
-  modifier: Modifier = Modifier,
-) {
-  val saved by produceState(false, item) { value = isSaved(item) }
-  LobstersCard(
-    post = item,
-    isSaved = saved,
-    postActions = postActions,
-    modifier = modifier,
-  )
-}

android/src/main/kotlin/dev/msfjarvis/claw/android/ui/lists/NetworkPosts.kt

@@ -27,19 +27,18 @@ import androidx.compose.ui.unit.dp
 import androidx.paging.LoadState
 import androidx.paging.compose.LazyPagingItems
 import androidx.paging.compose.items
+import dev.msfjarvis.claw.common.posts.LobstersCard
 import dev.msfjarvis.claw.common.posts.PostActions
 import dev.msfjarvis.claw.common.posts.toDbModel
 import dev.msfjarvis.claw.common.ui.NetworkError
 import dev.msfjarvis.claw.common.ui.ProgressBar
-import dev.msfjarvis.claw.database.local.SavedPost
 import dev.msfjarvis.claw.model.LobstersPost
 
 @OptIn(ExperimentalMaterialApi::class)
 @Composable
 fun NetworkPosts(
-  lazyPagingItems: LazyPagingItems<LobstersPost>,
+  lazyPagingItems: LazyPagingItems<Pair<LobstersPost, Boolean>>,
   listState: LazyListState,
-  isPostSaved: suspend (SavedPost) -> Boolean,
   postActions: PostActions,
   modifier: Modifier = Modifier,
 ) {
@@ -59,10 +58,10 @@ fun NetworkPosts(
       ) {
         items(lazyPagingItems) { item ->
           if (item != null) {
-            val dbModel = item.toDbModel()
-            ListItem(
-              item = dbModel,
-              isSaved = isPostSaved,
+            val (post, saved) = item
+            LobstersCard(
+              post = post.toDbModel(),
+              isSaved = saved,
               postActions = postActions,
             )
 

android/src/main/kotlin/dev/msfjarvis/claw/android/viewmodel/ClawViewModel.kt

@@ -10,6 +10,8 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import androidx.paging.Pager
 import androidx.paging.PagingConfig
+import androidx.paging.cachedIn
+import androidx.paging.map
 import com.deliveryhero.whetstone.viewmodel.ContributesViewModel
 import com.slack.eithernet.ApiResult.Failure
 import com.slack.eithernet.ApiResult.Success
@@ -43,10 +45,16 @@ constructor(
     Pager(PagingConfig(pageSize = 20)) { pagingSourceFactory.create(api::getHottestPosts) }
 
   val hottestPosts
-    get() = hottestPostsPager.flow
+    get() =
+      hottestPostsPager.flow
+        .map { pagingData -> pagingData.map { item -> item to isPostSaved(item.shortId) } }
+        .cachedIn(viewModelScope)
 
   val newestPosts
-    get() = newestPostsPager.flow
+    get() =
+      newestPostsPager.flow
+        .map { pagingData -> pagingData.map { item -> item to isPostSaved(item.shortId) } }
+        .cachedIn(viewModelScope)
 
   private val savedPostsFlow
     get() = savedPostsRepository.savedPosts
@@ -59,13 +67,13 @@ constructor(
     return sorted.groupBy { post -> post.createdAt.toLocalDateTime().month }
   }
 
-  suspend fun isPostSaved(post: SavedPost): Boolean {
-    return savedPostsFlow.first().any { savedPost -> savedPost.shortId == post.shortId }
+  private suspend fun isPostSaved(shortId: String): Boolean {
+    return savedPostsFlow.first().any { savedPost -> savedPost.shortId == shortId }
   }
 
   fun toggleSave(post: SavedPost) {
     viewModelScope.launch(ioDispatcher) {
-      val saved = isPostSaved(post)
+      val saved = isPostSaved(post.shortId)
       if (saved) {
         savedPostsRepository.removePost(post)
       } else {