app: reinstate API wrapper to hide client implementation

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

app/proguard-rules.pro

@@ -8,3 +8,11 @@
 -keepclasseswithmembers class dev.msfjarvis.lobsters.model.** {
     kotlinx.serialization.KSerializer serializer(...);
 }
+
+# Workaround for https://github.com/ktorio/ktor/issues/1354
+-keepclassmembers class io.ktor.** { volatile <fields>; }
+
+# Workaround for https://github.com/Kotlin/kotlinx.coroutines/issues/1564
+-keepclassmembers class kotlinx.** {
+    volatile <fields>;
+}

app/src/main/java/dev/msfjarvis/lobsters/data/api/KtorLobstersApi.kt

@@ -0,0 +1,16 @@
+package dev.msfjarvis.lobsters.data.api
+
+import dev.msfjarvis.lobsters.data.api.LobstersApi.Companion.BASE_URL
+import dev.msfjarvis.lobsters.model.LobstersPost
+import io.ktor.client.HttpClient
+import io.ktor.client.request.get
+import javax.inject.Inject
+
+/**
+ * Ktor backed implementation of [LobstersApi]
+ */
+class KtorLobstersApi @Inject constructor(private val client: HttpClient) : LobstersApi {
+  override suspend fun getHottestPosts(page: Int): List<LobstersPost> {
+    return client.get("${BASE_URL}/hottest.json?page=$page")
+  }
+}

app/src/main/java/dev/msfjarvis/lobsters/data/api/LobstersApi.kt

@@ -0,0 +1,15 @@
+package dev.msfjarvis.lobsters.data.api
+
+import dev.msfjarvis.lobsters.model.LobstersPost
+
+/**
+ * Simple interface defining an API for lobste.rs
+ */
+interface LobstersApi {
+
+  suspend fun getHottestPosts(page: Int): List<LobstersPost>
+
+  companion object {
+    const val BASE_URL = "https://lobste.rs"
+  }
+}

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

@@ -1,26 +1,14 @@
 package dev.msfjarvis.lobsters.injection
 
+import dagger.Binds
 import dagger.Module
-import dagger.Provides
 import dagger.hilt.InstallIn
-import dagger.hilt.android.components.ApplicationComponent
-import io.ktor.client.HttpClient
-import io.ktor.client.engine.okhttp.OkHttp
-import io.ktor.client.features.json.JsonFeature
-import io.ktor.client.features.json.serializer.KotlinxSerializer
+import dagger.hilt.android.components.ActivityComponent
+import dev.msfjarvis.lobsters.data.api.KtorLobstersApi
+import dev.msfjarvis.lobsters.data.api.LobstersApi
 
 @Module
-@InstallIn(ApplicationComponent::class)
-object KtorApiModule {
-  @Provides
-  fun provideClient() = HttpClient(OkHttp) {
-    install(JsonFeature) {
-      serializer = KotlinxSerializer()
-    }
-    engine {
-      config {
-        followSslRedirects(true)
-      }
-    }
-  }
+@InstallIn(ActivityComponent::class)
+abstract class KtorApiModule {
+  @Binds abstract fun bindLobstersApi(realApi: KtorLobstersApi): LobstersApi
 }

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

@@ -0,0 +1,26 @@
+package dev.msfjarvis.lobsters.injection
+
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.components.ApplicationComponent
+import io.ktor.client.HttpClient
+import io.ktor.client.engine.okhttp.OkHttp
+import io.ktor.client.features.json.JsonFeature
+import io.ktor.client.features.json.serializer.KotlinxSerializer
+
+@Module
+@InstallIn(ApplicationComponent::class)
+object KtorClientModule {
+  @Provides
+  fun provideClient() = HttpClient(OkHttp) {
+    install(JsonFeature) {
+      serializer = KotlinxSerializer()
+    }
+    engine {
+      config {
+        followSslRedirects(true)
+      }
+    }
+  }
+}

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

@@ -3,10 +3,9 @@ package dev.msfjarvis.lobsters.ui.viewmodel
 import androidx.hilt.lifecycle.ViewModelInject
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import dev.msfjarvis.lobsters.data.api.LobstersApi
 import dev.msfjarvis.lobsters.data.source.PostsDatabase
 import dev.msfjarvis.lobsters.model.LobstersPost
-import io.ktor.client.HttpClient
-import io.ktor.client.request.get
 import kotlinx.coroutines.CoroutineExceptionHandler
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
@@ -16,7 +15,7 @@ import java.net.SocketTimeoutException
 import java.net.UnknownHostException
 
 class LobstersViewModel @ViewModelInject constructor(
-  private val client: HttpClient,
+  private val lobstersApi: LobstersApi,
   database: PostsDatabase,
 ) : ViewModel() {
   private var apiPage = 1
@@ -57,7 +56,7 @@ class LobstersViewModel @ViewModelInject constructor(
 
   private fun getMorePostsInternal(firstLoad: Boolean) {
     viewModelScope.launch(coroutineExceptionHandler) {
-      val newPosts = client.get<List<LobstersPost>>("https://lobste.rs/hottest.json?page=$apiPage")
+      val newPosts = lobstersApi.getHottestPosts(apiPage)
       if (firstLoad) {
         _posts.value = newPosts
         postsDao.deleteAllPosts()