Migrate to ui state

Author: Drjacky

core/network/src/main/java/app/web/drjackycv/core/network/entity/Result.kt

@@ -0,0 +1,37 @@
+package app.web.drjackycv.core.network.entity
+
+import app.web.drjackycv.common.exceptions.Failure
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onStart
+import java.net.SocketTimeoutException
+import java.net.UnknownHostException
+import java.util.concurrent.TimeoutException
+
+sealed interface Result<out T> {
+    data class Success<T>(val data: T) : Result<T>
+    data class Error(val failure: Failure) : Result<Nothing>
+    object Loading : Result<Nothing>
+}
+
+fun <T> Flow<T>.asResult(): Flow<Result<T>> {
+    return this
+        .map<T, Result<T>> {
+            Result.Success(it)
+        }
+        .onStart { emit(Result.Loading) }
+        .catch { e ->
+            when (e) {
+                is UnknownHostException, is SocketTimeoutException -> {
+                    emit(Result.Error(Failure.NoInternet(e.message)))
+                }
+                is TimeoutException -> {
+                    emit(Result.Error(Failure.Timeout(e.message)))
+                }
+                else -> {
+                    emit(Result.Error(Failure.Unknown(e.message)))
+                }
+            }
+        }
+}

features/characters/src/main/java/app/web/drjackycv/features/characters/data/CharactersPagingSource.kt

@@ -39,7 +39,7 @@ class CharactersPagingSource @Inject constructor(
 
                 toLoadResult(responseCharacters, position)
             } catch (e: Exception) {
-                when (e) {
+                when (e.cause?.cause) {
                     is UnknownHostException, is SocketTimeoutException -> {
                         LoadResult.Error(
                             Failure.NoInternet(e.message)

features/characters/src/main/java/app/web/drjackycv/features/characters/presentation/Characters.kt

@@ -11,7 +11,6 @@ import androidx.navigation.fragment.FragmentNavigatorExtras
 import androidx.navigation.fragment.findNavController
 import androidx.paging.CombinedLoadStates
 import androidx.paging.LoadState
-import androidx.paging.PagingData
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import app.web.drjackycv.common.exceptions.Failure
@@ -83,10 +82,18 @@ class Characters : Fragment(R.layout.characters) {
         }
     }
 
-    private fun addCharactersList(charactersList: PagingData<CharacterDetail>) {
-        loadingUI(false)
-        binding.rvCharactersList.visible()
-        charactersAdapter.submitData(lifecycle, charactersList)
+    private fun addCharactersList(uiState: CharactersUiState) {
+        when (uiState) {
+            is CharactersUiState.Success -> {
+                loadingUI(false)
+                binding.rvCharactersList.visible()
+                charactersAdapter.submitData(lifecycle, uiState.items)
+            }
+            else -> {
+                //no-op: is handled by addLoadStateListener
+            }
+        }
+
     }
 
     private fun loadingUI(isLoading: Boolean) {

features/characters/src/main/java/app/web/drjackycv/features/characters/presentation/CharactersListViewModel.kt

@@ -8,14 +8,13 @@ import androidx.paging.PagingData
 import androidx.paging.cachedIn
 import app.web.drjackycv.common.exceptions.Failure
 import app.web.drjackycv.common.models.fragment.CharacterDetail
+import app.web.drjackycv.core.network.entity.Result
+import app.web.drjackycv.core.network.entity.asResult
 import app.web.drjackycv.features.characters.R
 import app.web.drjackycv.features.characters.domain.GetCharactersListUseCase
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.channels.Channel
-import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.flow.receiveAsFlow
+import kotlinx.coroutines.flow.*
 import kotlinx.coroutines.launch
 import javax.inject.Inject
 
@@ -30,21 +29,32 @@ class CharactersListViewModel @Inject constructor(
 
     private val _failure: Channel<Failure> = Channel(Channel.BUFFERED)
     val failure: Flow<Failure> = _failure.receiveAsFlow()
-    private val _charactersList =
-        MutableStateFlow<PagingData<CharacterDetail>>(PagingData.empty())
-    val charactersList: Flow<PagingData<CharacterDetail>> = _charactersList
 
-
-    init {
+    val charactersList: StateFlow<CharactersUiState> =
         getCharacters()
-    }
+            .stateIn(
+                scope = viewModelScope,
+                started = SharingStarted.WhileSubscribed(5000),
+                initialValue = CharactersUiState.Loading
+            )
 
-    private fun getCharacters() {
-        viewModelScope.launch {
-            _charactersList.value = getCharactersListUseCase()
-                .cachedIn(viewModelScope).first()
-        }
-    }
+    private fun getCharacters() =
+        getCharactersListUseCase()
+            .cachedIn(viewModelScope)
+            .asResult()
+            .map { result ->
+                when (result) {
+                    is Result.Success -> {
+                        CharactersUiState.Success(result.data)
+                    }
+                    is Result.Error -> {
+                        CharactersUiState.Error(result.failure)
+                    }
+                    is Result.Loading -> {
+                        CharactersUiState.Loading
+                    }
+                }
+            }
 
     fun handleFailure(throwable: Throwable, retryAction: () -> Unit) {
         val failure = when (throwable) {
@@ -71,4 +81,12 @@ class CharactersListViewModel @Inject constructor(
         }
     }
 
+}
+
+sealed interface CharactersUiState {
+    data class Success(val items: PagingData<CharacterDetail> = PagingData.empty()) :
+        CharactersUiState
+
+    data class Error(val error: Failure) : CharactersUiState
+    object Loading : CharactersUiState
 }