NetworkModule.java

@Module
public class NetworkModule {

  static final String RETROFIT_GITHUB = "GitHub";
  static final String RETROFIT_GITHUB_STATUS = "GitHubStatus";
  static final String RETROFIT_GITHUB_OAUTH = "GitHubOAuth";

  private static final int CACHE_SIZE_10_MB = 10 * 1024 * 1024;

  @Provides
  @Singleton
  Cache providesOkHttpCache(Application application) {
      int cacheSize = CACHE_SIZE_10_MB;
      return new Cache(application.getCacheDir(), cacheSize);
  }

  @Provides
  @Singleton
  Gson providesGson() {
      return new GsonBuilder()
              .setDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'")
              .create();
  }

  @Provides
  @Singleton
  HttpLoggingInterceptor providesHttpLoggingInterceptor() {
      final HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
      interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
      return interceptor;
  }

  @Provides
  @Singleton
  OkHttpClient providesOkHttpClient(Cache cache,
                                    HttpLoggingInterceptor interceptor) {
      return new OkHttpClient.Builder()
              .addInterceptor(interceptor)
              .cache(cache).build();
  }

  @Provides
  @Singleton
  GsonConverterFactory providesGsonConverterFactory(Gson gson) {
      return GsonConverterFactory.create(gson);
  }

  @Provides
  @Singleton
  RxJavaCallAdapterFactory providesRxJavaCallAdapterFactory() {
      return RxJavaCallAdapterFactory.create();
  }

  @Provides
  @Singleton
  @Named(RETROFIT_GITHUB)
  Retrofit providesRetrofitGitHub(OkHttpClient okHttpClient,
                                  GsonConverterFactory gsonFactory,
                                  RxJavaCallAdapterFactory rxFactory) {
      return buildRetrofit(okHttpClient,
              gsonFactory,
              rxFactory,
              GitHubService.BASE_URL);
  }

  @Provides
  @Singleton
  @Named(RETROFIT_GITHUB_STATUS)
  Retrofit providesRetrofitGitHubStatus(OkHttpClient okHttpClient,
                                        GsonConverterFactory gsonFactory,
                                        RxJavaCallAdapterFactory rxFactory) {
      return buildRetrofit(okHttpClient,
              gsonFactory,
              rxFactory,
              GitHubStatusService.BASE_URL);
  }

  @Provides
  @Singleton
  @Named(RETROFIT_GITHUB_OAUTH)
  Retrofit providesRetrofitGitHubOAuth(OkHttpClient okHttpClient,
                                       GsonConverterFactory gsonFactory,
                                       RxJavaCallAdapterFactory rxFactory) {
      return buildRetrofit(okHttpClient,
              gsonFactory,
              rxFactory,
              GitHubOAuthService.BASE_URL);
  }

  private Retrofit buildRetrofit(OkHttpClient okHttpClient,
                                 GsonConverterFactory converterFactory,
                                 RxJavaCallAdapterFactory callAdapterFactory,
                                 String baseUrl) {
      return new Retrofit.Builder()
              .baseUrl(baseUrl)
              .client(okHttpClient)
              .addConverterFactory(converterFactory)
              .addCallAdapterFactory(callAdapterFactory)
              .build();
  }
}