Adds Either class for livedata handling (#14)

* 🎉 Initial structure for the Either refactor

* ♻️ Adds Either class for livedata handling

data/src/main/kotlin/com/hernandazevedo/moviedb/data/Logger.kt

@@ -18,6 +18,10 @@ object Logger {
         Timber.tag(UNIQUE_TAG).e(e)
     }
 
+    fun e( e: Throwable, msg: String) {
+        Timber.tag(UNIQUE_TAG).e(e, msg)
+    }
+
     fun init() {
         if (BuildConfig.DEBUG) Timber.plant(Timber.DebugTree())
     }

presentation/src/main/kotlin/com/hernandazevedo/moviedb/view/base/Either.kt

@@ -0,0 +1,45 @@
+package com.hernandazevedo.moviedb.view.base
+
+/**
+ * Based on https://medium.com/@lupajz/you-either-love-it-or-you-havent-used-it-yet-a55f9b866dbe
+ */
+sealed class Either<out E, out V> {
+    data class Left<out E>(val error: E) : Either<E, Nothing>()
+    data class Right<out V>(val value: V) : Either<Nothing, V>()
+
+    fun <V> right(value: V): Either<Nothing, V> = Either.Right(value)
+    fun <E> left(value: E): Either<E, Nothing> = Either.Left(value)
+
+    fun <V> either(action: () -> V): Either<Exception, V> =
+            try { right(action()) } catch (e: Exception) { left(e) }
+}
+
+inline infix fun <E, V, V2> Either<E, V>
+        .map(f: (V) -> V2): Either<E, V2> = when (this) {
+    is Either.Left -> this
+    is Either.Right -> Either.Right(f(this.value))
+}
+
+infix fun <E, V, V2> Either<E, (V) -> V2>
+        .apply(f: Either<E, V>): Either<E, V2> = when (this) {
+    is Either.Left -> this
+    is Either.Right -> f.map(this.value)
+}
+
+inline infix fun <E, V, V2> Either<E, V>
+        .flatMap(f: (V) -> Either<E, V2>): Either<E, V2> = when (this) {
+    is Either.Left -> this
+    is Either.Right -> f(value)
+}
+
+inline infix fun <E, E2, V> Either<E, V>
+        .mapError(f: (E) -> E2): Either<E2, V> = when (this) {
+    is Either.Left -> Either.Left(f.invoke(error))
+    is Either.Right -> this
+}
+
+inline fun <E, V, A> Either<E, V>
+        .fold(e: (E) -> A, v: (V) -> A): A = when (this) {
+    is Either.Left -> e(this.error)
+    is Either.Right -> v(this.value)
+}

presentation/src/main/kotlin/com/hernandazevedo/moviedb/view/details/DetailsActivity.kt

@@ -13,8 +13,7 @@ import com.hernandazevedo.moviedb.R
 import com.hernandazevedo.moviedb.data.Logger
 import com.hernandazevedo.moviedb.getFactoryViewModel
 import com.hernandazevedo.moviedb.view.base.BaseActivity
-import com.hernandazevedo.moviedb.view.base.Resource
-import com.hernandazevedo.moviedb.view.base.Status
+import com.hernandazevedo.moviedb.view.base.fold
 import kotlinx.android.synthetic.main.activity_details.*
 import javax.inject.Inject
 
@@ -35,6 +34,7 @@ class DetailsActivity : BaseActivity() {
         detailsViewModel = getFactoryViewModel { detailsViewModel }
         setContentView(R.layout.activity_details)
         subscribeToSearchMovie()
+        subscribeToFavoriteMovie()
         shareAction.setOnClickListener { setupShareAction() }
         populateInfo()
         setupFavAction()
@@ -43,18 +43,24 @@ class DetailsActivity : BaseActivity() {
 
     private fun subscribeToSearchMovie() {
         detailsViewModel.responseGetMovieDetails.observe(this,
-            Observer<Resource<MovieDetail>> {
-                when (it?.status) {
-                    Status.SUCCESS -> {
-                        Logger.d("Success finding movie details")
-                        fillMovieDetail(it.data)
-                    }
-                    Status.ERROR -> {
-                        Logger.d("Error finding movie details")
-                        showMessage("Error finding movie details")
-                        it.throwable?.printStackTrace()
-                    }
-                }
+            Observer {
+                it?.fold({ e: Throwable ->
+                    Logger.e(e, "Left finding movie details")
+                    showMessage("Left finding movie details")
+                }, {})
+            })
+    }
+
+    private fun subscribeToFavoriteMovie() {
+        detailsViewModel.responseFavoriteAction.observe(this,
+            Observer {
+                it?.fold(
+                    { e: Throwable ->
+                        Logger.e(e, "Left finding movie details")
+                        showMessage("Left finding movie details")
+                    },
+                    {}
+                )
             })
     }
 
@@ -81,7 +87,7 @@ class DetailsActivity : BaseActivity() {
             movieTitle.text = "# ${movie.title}"
             movieYear.text = year
             movieVoteAverage.text = "'-'"
-            favoriteButton.isChecked = favored ?: false
+            favoriteButton.isChecked = favored
 
             movieAdultImage.setImageDrawable(getDrawable(R.drawable.ic_clapperboard))
             //TODO

presentation/src/main/kotlin/com/hernandazevedo/moviedb/view/details/DetailsViewModel.kt

@@ -10,16 +10,16 @@ import com.hernandazevedo.moviedb.domain.usecase.request.GetMovieDetailsRequest
 import com.hernandazevedo.moviedb.domain.usecase.request.SaveMovieToLocalDatabaseRequest
 import com.hernandazevedo.moviedb.util.UseCaseHandler
 import com.hernandazevedo.moviedb.view.base.BaseViewModel
-import com.hernandazevedo.moviedb.view.base.Resource
+import com.hernandazevedo.moviedb.view.base.Either
 
 class DetailsViewModel(
     val getMovieDetailsUseCase: BaseUseCase<GetMovieDetailsRequest, MovieDetail>,
     val saveMovieToLocalDatabaseUseCase: BaseUseCase<SaveMovieToLocalDatabaseRequest, Long>,
     val deleteMovieFromLocalDatabaseUseCase: BaseUseCase<DeleteMovieFromLocalDatabaseRequest, Long>
 ) : BaseViewModel() {
 
-    val responseGetMovieDetails: MutableLiveData<Resource<MovieDetail>> = MutableLiveData()
-    val rsponseFavoriteAction: MutableLiveData<Resource<Any>> = MutableLiveData()
+    val responseGetMovieDetails: MutableLiveData<Either<Throwable, MovieDetail>> = MutableLiveData()
+    val responseFavoriteAction: MutableLiveData<Either<Throwable, Any>> = MutableLiveData()
 
     fun getMovieDetails(imdbID: String) {
         Logger.d("Starting getMovieDetails - $imdbID")
@@ -29,10 +29,10 @@ class DetailsViewModel(
             useCaseExecute
                 .subscribe({
                     Logger.d("Success searching movies for imdbID $imdbID")
-                    responseGetMovieDetails.value = Resource.success(it)
+                    responseGetMovieDetails.value = Either.Right(it)
                 }, {
-                    Logger.d("Error searching movies for imdbID $imdbID")
-                    responseGetMovieDetails.value = Resource.error(it)
+                    Logger.d("Left searching movies for imdbID $imdbID")
+                    responseGetMovieDetails.value = Either.Left(it)
                 }))
     }
 
@@ -51,10 +51,10 @@ class DetailsViewModel(
             useCaseExecute
                 .subscribe({
                     Logger.d("Success favoriteAction $checked")
-                    responseGetMovieDetails.value = Resource.success()
+                    responseFavoriteAction.value = Either.Right(Any())
                 }, {
-                    Logger.d("Error favoriteAction $checked")
-                    responseGetMovieDetails.value = Resource.error(it)
+                    Logger.d("Left favoriteAction $checked")
+                    responseFavoriteAction.value = Either.Left(it)
                 }))
     }
 }

presentation/src/main/kotlin/com/hernandazevedo/moviedb/view/main/MainActivity.kt

@@ -16,8 +16,7 @@ import com.hernandazevedo.moviedb.getFactoryViewModel
 import com.hernandazevedo.moviedb.view.Navigator
 import com.hernandazevedo.moviedb.view.adapter.MovieAdapter
 import com.hernandazevedo.moviedb.view.base.BaseActivity
-import com.hernandazevedo.moviedb.view.base.Resource
-import com.hernandazevedo.moviedb.view.base.Status
+import com.hernandazevedo.moviedb.view.base.fold
 import kotlinx.android.synthetic.main.activity_main.*
 import kotlinx.android.synthetic.main.activity_movies.*
 import javax.inject.Inject
@@ -73,26 +72,21 @@ class MainActivity : BaseActivity() , NavigationView.OnNavigationItemSelectedLis
     }
 
     private fun subscribeToSearchMovie() {
-        mainViewModel.responseSearchMovie.observe(this,
-            Observer<Resource<List<Movie>>> {
-                when (it?.status) {
-                    Status.SUCCESS -> {
-                        Logger.d("Success finding movie")
-                        showMovies(it.data)
-                    }
-                    Status.ERROR -> {
-                        Logger.d("Error finding movie")
-                        showMessage("Error finding movie")
-                        it.throwable?.printStackTrace()
-                    }
-                }
-            })
+        mainViewModel.responseSearchMovie.observe(this, Observer {
+            it?.fold(this::handleError, this::showMovies)
+        })
     }
 
-    private fun showMovies(movieList: List<Movie>?) {
+    private fun showMovies(movieList: List<Movie>) {
+        Logger.d("Success finding movie")
         movieAdapter.setMovies(movieList)
     }
 
+    private fun handleError(e: Throwable) {
+        Logger.e(e, "Left finding movie")
+        showMessage("Left finding movie")
+    }
+
     private fun setupRecyclersView() {
         moviesRecyclerView.layoutManager = layoutManager
         moviesRecyclerView.adapter = movieAdapter

presentation/src/main/kotlin/com/hernandazevedo/moviedb/view/main/MainViewModel.kt

@@ -8,12 +8,12 @@ import com.hernandazevedo.moviedb.domain.usecase.base.BaseUseCase
 import com.hernandazevedo.moviedb.domain.usecase.request.SearchMovieRequest
 import com.hernandazevedo.moviedb.util.UseCaseHandler
 import com.hernandazevedo.moviedb.view.base.BaseViewModel
-import com.hernandazevedo.moviedb.view.base.Resource
+import com.hernandazevedo.moviedb.view.base.Either
 
 open class MainViewModel(val searchMovieUseCase: BaseUseCase<SearchMovieRequest, List<Movie>>,
                          val fetchMyFavoritesUseCase: BaseUseCase<BaseRequestValues, List<Movie>>) : BaseViewModel() {
     //Here could be an object created on presentation layer, but to be simple we are using the domain model.
-    val responseSearchMovie: MutableLiveData<Resource<List<Movie>>> = MutableLiveData()
+    val responseSearchMovie: MutableLiveData<Either<Throwable, List<Movie>>> = MutableLiveData()
 
     fun searchMovie(title: String) {
         Logger.d("Starting searchMovie - $title")
@@ -23,10 +23,10 @@ open class MainViewModel(val searchMovieUseCase: BaseUseCase<SearchMovieRequest,
             useCaseExecute
                 .subscribe({
                     Logger.d("Success searching movies for title $title")
-                    responseSearchMovie.value = Resource.success(it)
+                    responseSearchMovie.value = Either.Right(it)
                 }, {
-                    Logger.d("Error searching movies for title $title")
-                    responseSearchMovie.value = Resource.error(it)
+                    Logger.d("Left searching movies for title $title")
+                    responseSearchMovie.value = Either.Left(it)
                 }))
     }
 
@@ -38,10 +38,10 @@ open class MainViewModel(val searchMovieUseCase: BaseUseCase<SearchMovieRequest,
             useCaseExecute
                 .subscribe({
                     Logger.d("Success searching favorited movies")
-                    responseSearchMovie.value = Resource.success(it)
+                    responseSearchMovie.value = Either.Right(it)
                 }, {
-                    Logger.d("Error searching favorited movies")
-                    responseSearchMovie.value = Resource.error(it)
+                    Logger.d("Left searching favorited movies")
+                    responseSearchMovie.value = Either.Left(it)
                 }))
     }
 }

presentation/src/test/kotlin/com/hernandazevedo/moviedb/view/main/MainViewModelTest.kt

@@ -7,7 +7,7 @@ import com.hernandazevedo.moviedb.domain.usecase.base.BaseRequestValues
 import com.hernandazevedo.moviedb.domain.usecase.base.BaseUseCase
 import com.hernandazevedo.moviedb.domain.usecase.request.SearchMovieRequest
 import com.hernandazevedo.moviedb.rx.RxImmediateSchedulerRule
-import com.hernandazevedo.moviedb.view.base.Resource
+import com.hernandazevedo.moviedb.view.base.Either
 import com.nhaarman.mockito_kotlin.any
 import com.nhaarman.mockito_kotlin.given
 import com.nhaarman.mockito_kotlin.mock
@@ -55,8 +55,8 @@ class MainViewModelTest {
 
     @Test
     fun shouldSearchMovieTest() {
-        val expectedResult: MutableLiveData<com.hernandazevedo.moviedb.view.base.Resource<List<Movie>>> = MutableLiveData()
-        expectedResult.value = Resource.success(fakeMovieList)
+        val expectedResult: MutableLiveData<Either<Throwable, List<Movie>>> = MutableLiveData()
+        expectedResult.value = Either.Right(fakeMovieList)
         mainViewModel.searchMovie(fakeTitleSearch)
         Assert.assertEquals(expectedResult.value, mainViewModel.responseSearchMovie.value)
     }