feat(android): add DataTransferRepository

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

@@ -0,0 +1,54 @@
+/*
+ * Copyright © 2023 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.viewmodel
+
+import dev.msfjarvis.claw.android.injection.DatabaseDispatcher
+import dev.msfjarvis.claw.android.injection.IODispatcher
+import dev.msfjarvis.claw.database.LobstersDatabase
+import dev.msfjarvis.claw.database.SavedPostSerializer
+import dev.msfjarvis.claw.database.local.SavedPost
+import java.io.InputStream
+import java.io.OutputStream
+import javax.inject.Inject
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.builtins.ListSerializer
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromStream
+import kotlinx.serialization.json.encodeToStream
+
+@OptIn(ExperimentalSerializationApi::class)
+class DataTransferRepository
+@Inject
+constructor(
+  private val database: LobstersDatabase,
+  private val json: Json,
+  @DatabaseDispatcher private val dbDispatcher: CoroutineDispatcher,
+  @IODispatcher private val ioDispatcher: CoroutineDispatcher,
+) {
+  private val serializer = ListSerializer(SavedPostSerializer())
+  private val savedPostQueries = database.savedPostQueries
+
+  suspend fun importPosts(input: InputStream) {
+    val posts: List<SavedPost> =
+      withContext(ioDispatcher) {
+        json.decodeFromStream(
+          serializer,
+          input,
+        )
+      }
+    withContext(dbDispatcher) {
+      database.transaction { posts.forEach(savedPostQueries::insertOrReplacePost) }
+    }
+  }
+
+  suspend fun exportPosts(output: OutputStream) {
+    val posts = withContext(dbDispatcher) { savedPostQueries.selectAllPosts().executeAsList() }
+    withContext(ioDispatcher) { json.encodeToStream(serializer, posts, output) }
+  }
+}