Add LobstersRepo to handle DB operations

Signed-off-by: Aditya Wasan <adityawasan55@gmail.com>

app/build.gradle.kts

@@ -44,6 +44,7 @@ dependencies {
   implementation(Dependencies.Kotlin.Coroutines.android)
   implementation(Dependencies.ThirdParty.accompanist)
   implementation(Dependencies.ThirdParty.Moshi.lib)
+  implementation(Dependencies.ThirdParty.SQLDelight.androidDriver)
   testImplementation(Dependencies.Testing.junit)
   androidTestImplementation(Dependencies.Testing.daggerHilt)
   androidTestImplementation(Dependencies.Testing.uiTest)

app/src/main/java/dev/msfjarvis/lobsters/data/remote/LobstersPagingSource.kt

@@ -3,16 +3,21 @@ package dev.msfjarvis.lobsters.data.remote
 import androidx.paging.PagingSource
 import dev.msfjarvis.lobsters.data.api.LobstersApi
 import dev.msfjarvis.lobsters.data.local.LobstersPost
+import dev.msfjarvis.lobsters.data.repo.LobstersRepository
 import javax.inject.Inject
 
 class LobstersPagingSource @Inject constructor(
   private val lobstersApi: LobstersApi,
+  private val lobstersRepository: LobstersRepository,
 ) : PagingSource<Int, LobstersPost>() {
 
   override suspend fun load(params: LoadParams<Int>): LoadResult<Int, LobstersPost> {
     return try {
       val page = params.key ?: 1
-      val posts = lobstersApi.getHottestPosts(page)
+      val savedPosts = lobstersRepository.getCachedPosts()
+      val posts = lobstersApi.getHottestPosts(page).map { post ->
+        post.copy(is_saved = savedPosts.contains(post.short_id))
+      }
 
       LoadResult.Page(
         data = posts,

app/src/main/java/dev/msfjarvis/lobsters/data/repo/LobstersRepository.kt

@@ -0,0 +1,39 @@
+package dev.msfjarvis.lobsters.data.repo
+
+import dev.msfjarvis.lobsters.data.local.LobstersPost
+import dev.msfjarvis.lobsters.database.LobstersDatabase
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import javax.inject.Inject
+
+class LobstersRepository @Inject constructor(private val lobstersDatabase: LobstersDatabase) {
+
+  private var savedPostCache: MutableSet<String>? = null
+
+  fun isPostSaved(postId: String): Boolean {
+    savedPostCache ?: return false
+    return requireNotNull(savedPostCache).contains(postId)
+  }
+
+  suspend fun savePost(post: LobstersPost) = withContext(Dispatchers.IO) {
+    val isElementAdded = getCachedPosts().add(post.short_id)
+    if (isElementAdded) {
+      lobstersDatabase.postQueries.savePost(post.short_id)
+    }
+  }
+
+  suspend fun removeSavedPost(post: LobstersPost) = withContext(Dispatchers.IO) {
+    val isElementRemoved = getCachedPosts().remove(post.short_id)
+    if (isElementRemoved) {
+      lobstersDatabase.postQueries.removeSavedPost(post.short_id)
+    }
+  }
+
+  suspend fun getCachedPosts(): MutableSet<String> = withContext(Dispatchers.IO) {
+    if (savedPostCache != null) return@withContext requireNotNull(savedPostCache)
+
+    val dbPosts = lobstersDatabase.postQueries.selectSavedPosts().executeAsList()
+    savedPostCache = dbPosts.filter { it.is_saved ?: false }.map { it.short_id }.toMutableSet()
+    return@withContext requireNotNull(savedPostCache)
+  }
+}

app/src/main/java/dev/msfjarvis/lobsters/injection/DatabaseModule.kt

@@ -0,0 +1,29 @@
+package dev.msfjarvis.lobsters.injection
+
+import android.content.Context
+import com.squareup.sqldelight.android.AndroidSqliteDriver
+import com.squareup.sqldelight.db.SqlDriver
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import dev.msfjarvis.lobsters.data.local.LobstersPost
+import dev.msfjarvis.lobsters.database.LobstersDatabase
+import dev.msfjarvis.lobsters.model.SubmitterAdapter
+import dev.msfjarvis.lobsters.model.TagsAdapter
+
+@Module
+@InstallIn(SingletonComponent::class)
+object DatabaseModule {
+
+  @Provides
+  fun providesSqlDriver(@ApplicationContext context: Context): SqlDriver {
+    return AndroidSqliteDriver(LobstersDatabase.Schema, context)
+  }
+
+  @Provides
+  fun providesLobstersDatabase(sqlDriver: SqlDriver): LobstersDatabase {
+    return LobstersDatabase(sqlDriver, LobstersPost.Adapter(SubmitterAdapter(), TagsAdapter()))
+  }
+}

app/src/main/java/dev/msfjarvis/lobsters/ui/main/MainActivity.kt

@@ -78,14 +78,14 @@ fun LobstersApp() {
         HottestPosts(
           posts = hottestPosts,
           listState = hottestPostsListState,
-          saveAction = viewModel::savePost,
+          saveAction = viewModel::toggleSave,
           modifier = Modifier.padding(bottom = innerPadding.bottom),
         )
       }
       composable(Destination.Saved.route) {
         SavedPosts(
           posts = savedPosts,
-          saveAction = viewModel::removeSavedPost,
+          saveAction = viewModel::toggleSave,
           modifier = Modifier.padding(bottom = innerPadding.bottom),
         )
       }

app/src/main/java/dev/msfjarvis/lobsters/ui/posts/LobstersItem.kt

@@ -121,7 +121,7 @@ fun LobstersItem(
           },
       )
       IconResource(
-        resourceId = R.drawable.ic_favorite_border_24px,
+        resourceId = if (post.is_saved == true) R.drawable.ic_favorite_24px else R.drawable.ic_favorite_border_24px,
         modifier = Modifier
           .padding(8.dp)
           .clickable(

app/src/main/java/dev/msfjarvis/lobsters/ui/viewmodel/LobstersViewModel.kt

@@ -5,8 +5,9 @@ import androidx.lifecycle.viewModelScope
 import androidx.paging.Pager
 import androidx.paging.PagingConfig
 import dagger.hilt.android.lifecycle.HiltViewModel
-import dev.msfjarvis.lobsters.data.remote.LobstersPagingSource
 import dev.msfjarvis.lobsters.data.local.LobstersPost
+import dev.msfjarvis.lobsters.data.remote.LobstersPagingSource
+import dev.msfjarvis.lobsters.data.repo.LobstersRepository
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.launch
@@ -15,6 +16,7 @@ import javax.inject.Inject
 @HiltViewModel
 class LobstersViewModel @Inject constructor(
   private val pagingSource: LobstersPagingSource,
+  private val lobstersRepository: LobstersRepository,
 ) : ViewModel() {
   private val _savedPosts = MutableStateFlow<List<LobstersPost>>(emptyList())
   val savedPosts = _savedPosts.asStateFlow()
@@ -22,13 +24,24 @@ class LobstersViewModel @Inject constructor(
     pagingSource
   }.flow
 
-  fun savePost(post: LobstersPost) {
+  fun toggleSave(post: LobstersPost) {
     viewModelScope.launch {
+      val isSaved = lobstersRepository.isPostSaved(post.short_id)
+      if (isSaved) removeSavedPost(post) else savePost(post)
     }
   }
 
-  fun removeSavedPost(post: LobstersPost) {
+  private fun savePost(post: LobstersPost) {
     viewModelScope.launch {
+      lobstersRepository.savePost(post)
+      _savedPosts.value = _savedPosts.value + post
+    }
+  }
+
+  private fun removeSavedPost(post: LobstersPost) {
+    viewModelScope.launch {
+      lobstersRepository.removeSavedPost(post)
+      _savedPosts.value = _savedPosts.value - post
     }
   }
 }

database/src/main/sqldelight/dev/msfjarvis/lobsters/data/local/Post.sq

@@ -22,6 +22,11 @@ selectAllPosts:
 SELECT *
 FROM LobstersPost;
 
+selectSavedPosts:
+SELECT *
+FROM LobstersPost
+WHERE is_saved = 1;
+
 selectPost:
 SELECT *
 FROM LobstersPost