Feat/Custom Rx Adapter for Network Response Handling

data/src/main/kotlin/app/web/drjackycv/data/network/BaseApiService.kt

@@ -0,0 +1,5 @@
+package app.web.drjackycv.data.network
+
+typealias GenericNetworkResponse<S> = NetworkResponse<S, ErrorBody>
+
+interface BaseApiService

data/src/main/kotlin/app/web/drjackycv/data/network/BaseRetrofit.kt

@@ -13,11 +13,12 @@ import javax.inject.Singleton
 @Singleton
 class BaseRetrofit @Inject constructor(
     private val okHttpClient: OkHttpClient,
-    private val gson: Gson
+    private val gson: Gson,
 ) {
 
     val retrofit = Retrofit.Builder()
         .baseUrl(BuildConfig.BASE_URL)
+        .addCallAdapterFactory(RxJavaCustomCallAdapterFactory.create()) //Has to be on top of the other adapters
         .addConverterFactory(GsonConverterFactory.create(gson))
         .addCallAdapterFactory(RxJava3CallAdapterFactory.createWithScheduler(Schedulers.io()))
         .client(okHttpClient)

data/src/main/kotlin/app/web/drjackycv/data/network/ErrorBody.kt

@@ -0,0 +1,7 @@
+package app.web.drjackycv.data.network
+
+data class ErrorBody(
+    val statusCode: Int,
+    val error: String,
+    val message: String,
+)

data/src/main/kotlin/app/web/drjackycv/data/network/NetworkResponse.kt

@@ -0,0 +1,30 @@
+package app.web.drjackycv.data.network
+
+import java.io.IOException
+
+/**
+ * Represents the result of making a network request.
+ *
+ * @param T success body type for 2xx response.
+ * @param U error body type for non-2xx response.
+ */
+sealed class NetworkResponse<out T : Any, out U : Any> {
+
+    /**
+     * A request that resulted in a response with a 2xx status code that has a body.
+     */
+    data class Success<T : Any>(val body: T) : NetworkResponse<T, Nothing>()
+
+    /**
+     * A request that resulted in a response with a non-2xx status code.
+     */
+    data class ApiError<U : Any>(val body: U?, val code: Int?) :
+        NetworkResponse<Nothing, U>()
+
+    /**
+     * A request that didn't result in a response.
+     */
+    data class NetworkError(val error: IOException) :
+        NetworkResponse<Nothing, Nothing>()
+
+}

data/src/main/kotlin/app/web/drjackycv/data/network/RxJavaCustomCallAdapter.kt

@@ -0,0 +1,83 @@
+package app.web.drjackycv.data.network
+
+import io.reactivex.rxjava3.core.BackpressureStrategy
+import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.functions.Function
+import okhttp3.ResponseBody
+import retrofit2.Call
+import retrofit2.CallAdapter
+import retrofit2.Converter
+import retrofit2.HttpException
+import java.io.IOException
+import java.lang.reflect.Type
+
+internal class RxJavaCustomCallAdapter<T : Any, U : Any>(
+    private val successBodyType: Type,
+    private val delegateAdapter: CallAdapter<T, Observable<T>>,
+    private val errorConverter: Converter<ResponseBody, U>,
+    private val isFlowable: Boolean,
+    private val isSingle: Boolean,
+    private val isMaybe: Boolean,
+) : CallAdapter<T, Any> {
+
+    override fun adapt(call: Call<T>): Any =
+        delegateAdapter.adapt(call)
+            .flatMap {
+                Observable.just<NetworkResponse<T, U>>(
+                    NetworkResponse.Success(
+                        it
+                    )
+                )
+            }
+            .onErrorResumeNext(
+                Function<Throwable, Observable<NetworkResponse<T, U>>> { throwable ->
+                    when (throwable) {
+                        is HttpException -> {
+                            val error = throwable.response()?.errorBody()
+                            val errorBody = when {
+                                error == null -> null
+                                error.contentLength() == 0L -> null
+                                else -> {
+                                    try {
+                                        errorConverter.convert(error)
+                                    } catch (e: Exception) {
+                                        return@Function Observable.just(
+                                            NetworkResponse.NetworkError(
+                                                IOException(
+                                                    "Couldn't deserialize error body: ${error.string()}",
+                                                    e
+                                                )
+                                            )
+                                        )
+                                    }
+                                }
+                            }
+                            val apiError = NetworkResponse.ApiError(
+                                errorBody,
+                                throwable.response()?.code()
+                            )
+                            Observable.just(apiError)
+                        }
+                        is IOException -> {
+                            Observable.just(
+                                NetworkResponse.NetworkError(
+                                    throwable
+                                )
+                            )
+                        }
+                        else -> {
+                            throw throwable
+                        }
+                    }
+                }).run {
+                when {
+                    isFlowable -> this.toFlowable(BackpressureStrategy.LATEST)
+                    isSingle -> this.singleOrError()
+                    isMaybe -> this.singleElement()
+                    else -> this
+                }
+            }
+
+    override fun responseType(): Type = successBodyType
+
+}

data/src/main/kotlin/app/web/drjackycv/data/network/RxJavaCustomCallAdapterFactory.kt

@@ -0,0 +1,91 @@
+package app.web.drjackycv.data.network
+
+import com.google.gson.reflect.TypeToken
+import io.reactivex.rxjava3.core.Flowable
+import io.reactivex.rxjava3.core.Maybe
+import io.reactivex.rxjava3.core.Observable
+import io.reactivex.rxjava3.core.Single
+import retrofit2.CallAdapter
+import retrofit2.Retrofit
+import java.lang.reflect.ParameterizedType
+import java.lang.reflect.Type
+
+/**
+ * A [CallAdapter.Factory] which allows [NetworkResponse] objects to be returned from RxJava
+ * streams.
+ *
+ * Adding this class to [Retrofit] allows you to return [Observable], [Flowable], [Single], or
+ * [Maybe] types parameterized with [NetworkResponse] from service methods.
+ *
+ * Note: This adapter must be registered before an adapter that is capable of adapting RxJava
+ * streams.
+ */
+class RxJavaCustomCallAdapterFactory private constructor() : CallAdapter.Factory() {
+
+    companion object {
+        @JvmStatic
+        fun create() = RxJavaCustomCallAdapterFactory()
+    }
+
+    override fun get(
+        returnType: Type,
+        annotations: Array<Annotation>,
+        retrofit: Retrofit,
+    ): CallAdapter<*, *>? {
+        val rawType = getRawType(returnType)
+
+        val isFlowable = rawType === Flowable::class.java
+        val isSingle = rawType === Single::class.java
+        val isMaybe = rawType === Maybe::class.java
+        if (rawType !== Observable::class.java && !isFlowable && !isSingle && !isMaybe) {
+            return null
+        }
+
+        if (returnType !is ParameterizedType) {
+            throw IllegalStateException(
+                "${rawType.simpleName} return type must be parameterized as " +
+                        "${rawType.simpleName}<Foo> or ${rawType.simpleName}<? extends Foo>"
+            )
+        }
+
+        val observableEmissionType = getParameterUpperBound(0, returnType)
+        if (getRawType(observableEmissionType) != NetworkResponse::class.java) {
+            return null
+        }
+
+        if (observableEmissionType !is ParameterizedType) {
+            throw IllegalStateException(
+                "NetworkResponse must be parameterized as NetworkResponse<SuccessBody, ErrorBody>"
+            )
+        }
+
+        val successBodyType = getParameterUpperBound(0, observableEmissionType)
+        val delegateType = TypeToken.getParameterized(
+            Observable::class.java,
+            successBodyType
+        )
+        val delegateAdapter = retrofit.nextCallAdapter(
+            this,
+            delegateType.type,
+            annotations
+        )
+
+        val errorBodyType = getParameterUpperBound(1, observableEmissionType)
+        val errorBodyConverter = retrofit.nextResponseBodyConverter<Any>(
+            null,
+            errorBodyType,
+            annotations
+        )
+
+        @Suppress("UNCHECKED_CAST") // Type of delegateAdapter is not known at compile time.
+        return RxJavaCustomCallAdapter(
+            successBodyType,
+            delegateAdapter as CallAdapter<Any, Observable<Any>>,
+            errorBodyConverter,
+            isFlowable,
+            isSingle,
+            isMaybe
+        )
+    }
+
+}

data/src/main/kotlin/app/web/drjackycv/data/products/datasource/ProductsPagingSource.kt

@@ -2,6 +2,7 @@ package app.web.drjackycv.data.products.datasource
 
 import androidx.paging.PagingState
 import androidx.paging.rxjava3.RxPagingSource
+import app.web.drjackycv.data.network.NetworkResponse
 import app.web.drjackycv.data.products.entity.BeerMapper
 import app.web.drjackycv.data.products.remote.ProductsApi
 import app.web.drjackycv.domain.base.Failure
@@ -30,28 +31,36 @@ class ProductsPagingSource @Inject constructor(
 
         return productsApi.getBeersList(position, params.loadSize)
             .subscribeOn(Schedulers.io())
-            .map { listBeerResponse ->
-                listBeerResponse.map {
-                    BeerMapper().mapLeftToRight(it)
+            .map { response ->
+                when (response) {
+                    is NetworkResponse.Success -> {
+                        val list = response.body.map {
+                            BeerMapper().mapLeftToRight(it)
+                        }
+
+                        toLoadResult(list, position)
+                    }
+                    is NetworkResponse.ApiError -> {
+                        LoadResult.Error(Failure.Api(response.body?.message))
+                    }
+                    is NetworkResponse.NetworkError -> {
+                        LoadResult.Error(Failure.NoInternet(response.error.message))
+                    }
+                    else -> {
+                        LoadResult.Error(Failure.Unknown())
+                    }
                 }
             }
-            .map { toLoadResult(it, position) }
             .onErrorReturn { throwable ->
                 when (throwable) {
                     is UnknownHostException, is SocketTimeoutException -> {
-                        LoadResult.Error(
-                            Failure.NoInternet(throwable.message)
-                        )
+                        LoadResult.Error(Failure.NoInternet(throwable.message))
                     }
                     is TimeoutException -> {
-                        LoadResult.Error(
-                            Failure.Timeout(throwable.message)
-                        )
+                        LoadResult.Error(Failure.Timeout(throwable.message))
                     }
                     else -> {
-                        LoadResult.Error(
-                            Failure.Unknown(throwable.message)
-                        )
+                        LoadResult.Error(Failure.Unknown(throwable.message))
                     }
                 }
             }

data/src/main/kotlin/app/web/drjackycv/data/products/remote/ProductsApi.kt

@@ -1,24 +1,26 @@
 package app.web.drjackycv.data.products.remote
 
+import app.web.drjackycv.data.network.BaseApiService
+import app.web.drjackycv.data.network.GenericNetworkResponse
 import app.web.drjackycv.data.products.entity.BeerResponse
 import io.reactivex.rxjava3.core.Single
 import retrofit2.http.GET
 import retrofit2.http.Query
 
-interface ProductsApi {
+interface ProductsApi : BaseApiService {
 
     @GET("beers")
     fun getBeersList(
         /*@Query("ids") ids: String,*/
         @Query("page") page: Int = 1,
-        @Query("per_page") perPage: Int = 40
-    ): Single<List<BeerResponse>>
+        @Query("per_page") perPage: Int = 40,
+    ): Single<GenericNetworkResponse<List<BeerResponse>>>
 
     @GET("beers")
     suspend fun getBeersListByCoroutine(
         /*@Query("ids") ids: String,*/
         @Query("page") page: Int = 1,
-        @Query("per_page") perPage: Int = 40
+        @Query("per_page") perPage: Int = 40,
     ): List<BeerResponse>
 
 }

domain/src/main/kotlin/app/web/drjackycv/domain/base/Failure.kt

@@ -2,10 +2,12 @@ package app.web.drjackycv.domain.base
 
 sealed class Failure(var msg: String?, var retryAction: () -> Unit) : Throwable() {
 
-    class Timeout(msg: String?) : Failure(msg, {})
+    class Api(msg: String? = null) : Failure(msg, {})
 
-    class NoInternet(msg: String?) : Failure(msg, {})
+    class Timeout(msg: String? = null) : Failure(msg, {})
 
-    class Unknown(msg: String?) : Failure(msg, {})
+    class NoInternet(msg: String? = null) : Failure(msg, {})
+
+    class Unknown(msg: String? = null) : Failure(msg, {})
 
 }

domain/src/main/kotlin/app/web/drjackycv/domain/products/usecase/GetBeersListByCoroutineUseCase.kt

@@ -16,4 +16,5 @@ class GetBeersListByCoroutineUseCase @Inject constructor(
 
 }
 
-inline class GetBeersListByCoroutineParams(val ids: String)
+@JvmInline
+value class GetBeersListByCoroutineParams(val ids: String)

domain/src/main/kotlin/app/web/drjackycv/domain/products/usecase/GetBeersListUseCase.kt

@@ -16,4 +16,5 @@ class GetBeersListUseCase @Inject constructor(
 
 }
 
-inline class GetBeersListParams(val ids: String)
+@JvmInline
+value class GetBeersListParams(val ids: String)

presentation/src/main/kotlin/app/web/drjackycv/presentation/base/viewmodel/BaseViewModel.kt

@@ -56,6 +56,9 @@ open class BaseViewModel @Inject constructor() : ViewModel(),
             is Failure.NoInternet -> {
                 Failure.NoInternet(resources.getString(R.string.error_no_internet))
             }
+            is Failure.Api -> {
+                Failure.Api(throwable.msg)
+            }
             is Failure.Timeout -> {
                 Failure.Timeout(resources.getString(R.string.error_timeout))
             }