Use sandwich for constructing asynchronous request with API responses

README.md

@@ -36,6 +36,7 @@ Go to the [Releases](https://github.com/skydoves/MarvelHeroes/releases) to downl
   - [Koin](https://github.com/InsertKoinIO/koin) - dependency injection.
 - [Retrofit2 & Gson](https://github.com/square/retrofit) - construct the REST APIs.
 - [OkHttp3](https://github.com/square/okhttp) - implementing interceptor, logging and mocking web server.
+- [Sandwich](https://github.com/skydoves/Sandwich) - construct lightweight http API response and handling error responses.
 - [Glide](https://github.com/bumptech/glide) - loading images.
 - [TransformationLayout](https://github.com/skydoves/transformationlayout) - implementing transformation motion animations.
 - [WhatIf](https://github.com/skydoves/whatif) - checking nullable object and empty collections more fluently.

app/build.gradle

@@ -66,6 +66,7 @@ dependencies {
   implementation "org.koin:koin-android-viewmodel:$versions.koinVersion"
 
   // network
+  implementation "com.github.skydoves:sandwich:$versions.sandwichVersion"
   implementation "com.squareup.retrofit2:retrofit:$versions.retrofitVersion"
   implementation "com.squareup.okhttp3:logging-interceptor:$versions.okhttpVersion"
   implementation "com.squareup.retrofit2:converter-gson:$versions.retrofitVersion"

app/src/main/java/com/skydoves/marvelheroes/di/NetworkModule.kt

@@ -16,9 +16,11 @@
 
 package com.skydoves.marvelheroes.di
 
+import com.skydoves.marvelheroes.model.Poster
 import com.skydoves.marvelheroes.network.MarvelClient
 import com.skydoves.marvelheroes.network.MarvelService
 import com.skydoves.marvelheroes.network.RequestInterceptor
+import com.skydoves.sandwich.ResponseDataSource
 import okhttp3.OkHttpClient
 import org.koin.dsl.module
 import retrofit2.Retrofit
@@ -43,4 +45,6 @@ val networkModule = module {
   single { get<Retrofit>().create(MarvelService::class.java) }
 
   single { MarvelClient(get()) }
+
+  single { ResponseDataSource<List<Poster>>() }
 }

app/src/main/java/com/skydoves/marvelheroes/di/RepositoryModule.kt

@@ -22,7 +22,7 @@ import org.koin.dsl.module
 
 val repositoryModule = module {
 
-  single { MainRepository(get(), get()) }
+  single { MainRepository(get(), get(), get()) }
 
   single { DetailRepository(get()) }
 }

app/src/main/java/com/skydoves/marvelheroes/network/MarvelClient.kt

@@ -17,12 +17,23 @@
 package com.skydoves.marvelheroes.network
 
 import com.skydoves.marvelheroes.model.Poster
+import com.skydoves.sandwich.ApiResponse
+import com.skydoves.sandwich.ResponseDataSource
 
 class MarvelClient(private val marvelService: MarvelService) {
 
   fun fetchMarvelPosters(
+    dataSource: ResponseDataSource<List<Poster>>,
     onResult: (response: ApiResponse<List<Poster>>) -> Unit
   ) {
-    this.marvelService.fetchMarvelPosterList().transform(onResult)
+    dataSource
+      // retry fetching data 3 times with 5000 milli-seconds time interval when the request gets failure.
+      .retry(3, 5000L)
+      // combine network service to the data source.
+      .combine(marvelService.fetchMarvelPosterList(), onResult)
+      // request API network call asynchronously.
+      // if the request is successful, the data source will hold the success data.
+      // in the next request after success, returns the cached API response with data.
+      .request()
   }
 }

app/src/main/java/com/skydoves/marvelheroes/repository/MainRepository.kt

@@ -18,17 +18,21 @@ package com.skydoves.marvelheroes.repository
 
 import androidx.lifecycle.MutableLiveData
 import com.skydoves.marvelheroes.model.Poster
-import com.skydoves.marvelheroes.network.ApiResponse
 import com.skydoves.marvelheroes.network.MarvelClient
-import com.skydoves.marvelheroes.network.message
 import com.skydoves.marvelheroes.persistence.PosterDao
+import com.skydoves.sandwich.ResponseDataSource
+import com.skydoves.sandwich.message
+import com.skydoves.sandwich.onError
+import com.skydoves.sandwich.onException
+import com.skydoves.sandwich.onSuccess
 import com.skydoves.whatif.whatIfNotNull
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import timber.log.Timber
 
 class MainRepository constructor(
   private val marvelClient: MarvelClient,
+  private val marvelDataSource: ResponseDataSource<List<Poster>>,
   private val posterDao: PosterDao
 ) : Repository {
 
@@ -43,19 +47,23 @@ class MainRepository constructor(
     var posters = posterDao.getPosterList()
     if (posters.isEmpty()) {
       isLoading = true
-      marvelClient.fetchMarvelPosters { response ->
+      marvelClient.fetchMarvelPosters(marvelDataSource) { apiResponse ->
         isLoading = false
-        when (response) {
-          is ApiResponse.Success -> {
-            response.data.whatIfNotNull {
+        apiResponse
+          // handle the case when the API request gets a success response.
+          .onSuccess {
+            data.whatIfNotNull {
               posters = it
               liveData.postValue(it)
               posterDao.insertPosterList(it)
             }
           }
-          is ApiResponse.Failure.Error -> error(response.message())
-          is ApiResponse.Failure.Exception -> error(response.message())
-        }
+          // handle the case when the API request gets a error response.
+          // e.g. internal server error.
+          .onError { error(message()) }
+          // handle the case when the API request gets a exception response.
+          // e.g. network connection error.
+          .onException { error(message()) }
       }
     }
     liveData.apply { postValue(posters) }

app/src/test/java/com/skydoves/marvelheroes/network/ApiResponseTest.kt

@@ -16,6 +16,8 @@
 
 package com.skydoves.marvelheroes.network
 
+import com.skydoves.sandwich.ApiResponse
+import com.skydoves.sandwich.SandwichInitializer
 import org.hamcrest.CoreMatchers.`is`
 import org.hamcrest.MatcherAssert.assertThat
 import org.junit.Test
@@ -35,7 +37,8 @@ class ApiResponseTest {
 
   @Test
   fun success() {
-    val apiResponse = ApiResponse.of { Response.success("foo") }
+    val apiResponse =
+      ApiResponse.of(SandwichInitializer.successCodeRange) { Response.success("foo") }
     if (apiResponse is ApiResponse.Success) {
       assertThat(apiResponse.data, `is`("foo"))
     }

app/src/test/java/com/skydoves/marvelheroes/network/MarvelServiceTest.kt

@@ -19,6 +19,8 @@ package com.skydoves.marvelheroes.network
 import com.nhaarman.mockitokotlin2.mock
 import com.nhaarman.mockitokotlin2.whenever
 import com.skydoves.marvelheroes.model.Poster
+import com.skydoves.sandwich.ApiResponse
+import com.skydoves.sandwich.ResponseDataSource
 import java.io.IOException
 import org.hamcrest.CoreMatchers.`is`
 import org.hamcrest.CoreMatchers.instanceOf
@@ -49,6 +51,7 @@ class MarvelServiceTest : ApiAbstract<MarvelService>() {
     assertThat(responseBody[0].name, `is`("Deadpool"))
     assertThat(responseBody[0].color, `is`("#770609"))
 
+    val dataSource = ResponseDataSource<List<Poster>>()
     val onResult: (response: ApiResponse<List<Poster>>) -> Unit = {
       assertThat(it, instanceOf(ApiResponse.Success::class.java))
       val response: List<Poster> = requireNotNull((it as ApiResponse.Success).data)
@@ -57,11 +60,11 @@ class MarvelServiceTest : ApiAbstract<MarvelService>() {
       assertThat(response[0].color, `is`("#770609"))
     }
 
-    whenever(client.fetchMarvelPosters(onResult)).thenAnswer {
-      val response: (response: ApiResponse<List<Poster>>) -> Unit = it.getArgument(0)
+    whenever(client.fetchMarvelPosters(dataSource, onResult)).thenAnswer {
+      val response: (response: ApiResponse<List<Poster>>) -> Unit = it.getArgument(1)
       response(ApiResponse.Success(Response.success(responseBody)))
     }
 
-    client.fetchMarvelPosters(onResult)
+    client.fetchMarvelPosters(dataSource, onResult)
   }
 }

app/src/test/java/com/skydoves/marvelheroes/repository/MainRepositoryTest.kt

@@ -31,6 +31,7 @@ import com.skydoves.marvelheroes.network.MarvelClient
 import com.skydoves.marvelheroes.network.MarvelService
 import com.skydoves.marvelheroes.persistence.PosterDao
 import com.skydoves.marvelheroes.utils.MockTestUtil.mockPosterList
+import com.skydoves.sandwich.ResponseDataSource
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.runBlocking
 import org.junit.Before
@@ -44,6 +45,7 @@ class MainRepositoryTest {
   private lateinit var client: MarvelClient
   private val service: MarvelService = mock()
   private val posterDao: PosterDao = mock()
+  private val dataSource: ResponseDataSource<List<Poster>> = ResponseDataSource()
 
   @ExperimentalCoroutinesApi
   @get:Rule
@@ -56,7 +58,7 @@ class MainRepositoryTest {
   @Before
   fun setup() {
     client = MarvelClient(service)
-    repository = MainRepository(client, posterDao)
+    repository = MainRepository(client, dataSource, posterDao)
   }
 
   @Test

app/src/test/java/com/skydoves/marvelheroes/viewmodel/MainViewModelTest.kt

@@ -30,6 +30,7 @@ import com.skydoves.marvelheroes.persistence.PosterDao
 import com.skydoves.marvelheroes.repository.MainRepository
 import com.skydoves.marvelheroes.utils.MockTestUtil
 import com.skydoves.marvelheroes.view.ui.main.MainViewModel
+import com.skydoves.sandwich.ResponseDataSource
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.runBlocking
 import org.junit.Before
@@ -44,6 +45,7 @@ class MainViewModelTest {
   private val marvelService: MarvelService = mock()
   private val marvelClient: MarvelClient = MarvelClient(marvelService)
   private val posterDao: PosterDao = mock()
+  private val dataSource: ResponseDataSource<List<Poster>> = mock()
 
   @ExperimentalCoroutinesApi
   @get:Rule
@@ -55,7 +57,7 @@ class MainViewModelTest {
   @ExperimentalCoroutinesApi
   @Before
   fun setup() {
-    mainRepository = MainRepository(marvelClient, posterDao)
+    mainRepository = MainRepository(marvelClient, dataSource, posterDao)
     viewModel = MainViewModel(mainRepository)
   }
 

dependencies.gradle

@@ -27,12 +27,13 @@ ext.versions = [
     // network
     retrofitVersion     : '2.6.0',
     okhttpVersion       : '4.1.0',
+    sandwichVersion     : '1.0.0',
 
     // coroutines
     coroutinesVersion   : '1.3.0',
 
     // glide
-    glideVersion        : '4.9.0',
+    glideVersion        : '4.10.0',
 
     // transformation
     transformationLayout: '1.0.4',