Add last page detection to stop unnecessary API calls (#37)

* Add callback for last page reached

* Add last page reached check to prevent unnecessary fetches

* Clean up indentation of pokemonList logic in HomeViewModel

Author: jlkim909

core/data/src/main/kotlin/com/skydoves/pokedex/compose/core/data/repository/home/FakeHomeRepository.kt

@@ -25,6 +25,7 @@ class FakeHomeRepository : HomeRepository {
     page: Int,
     onStart: () -> Unit,
     onComplete: () -> Unit,
+    onLastPageReached: () -> Unit,
     onError: (String?) -> Unit,
   ): Flow<List<Pokemon>> = flowOf()
 }

core/data/src/main/kotlin/com/skydoves/pokedex/compose/core/data/repository/home/HomeRepository.kt

@@ -27,6 +27,7 @@ interface HomeRepository {
     page: Int,
     onStart: () -> Unit,
     onComplete: () -> Unit,
+    onLastPageReached: () -> Unit,
     onError: (String?) -> Unit,
   ): Flow<List<Pokemon>>
 }

core/data/src/main/kotlin/com/skydoves/pokedex/compose/core/data/repository/home/HomeRepositoryImpl.kt

@@ -48,6 +48,7 @@ class HomeRepositoryImpl @Inject constructor(
     page: Int,
     onStart: () -> Unit,
     onComplete: () -> Unit,
+    onLastPageReached: () -> Unit,
     onError: (String?) -> Unit,
   ) = flow {
     var pokemons = pokemonDao.getPokemonList(page).asDomain()
@@ -58,6 +59,10 @@ class HomeRepositoryImpl @Inject constructor(
        */
       val response = pokedexClient.fetchPokemonList(page = page)
       response.suspendOnSuccess {
+        if (data.next == null) {
+          onLastPageReached()
+        }
+
         pokemons = data.results
         pokemons.forEach { pokemon -> pokemon.page = page }
         pokemonDao.insertPokemonList(pokemons.asEntity())

feature/home/src/main/kotlin/com/skydoves/pokedex/compose/feature/home/HomeViewModel.kt

@@ -36,13 +36,15 @@ class HomeViewModel @Inject constructor(
 ) : BaseViewModel() {
 
   internal val uiState: ViewModelStateFlow<HomeUiState> = viewModelStateFlow(HomeUiState.Loading)
+  private var isLastPageReached = false
 
   private val pokemonFetchingIndex: MutableStateFlow<Int> = MutableStateFlow(0)
   val pokemonList: StateFlow<List<Pokemon>> = pokemonFetchingIndex.flatMapLatest { page ->
     homeRepository.fetchPokemonList(
       page = page,
       onStart = { uiState.tryEmit(key, HomeUiState.Loading) },
       onComplete = { uiState.tryEmit(key, HomeUiState.Idle) },
+      onLastPageReached = { isLastPageReached = true },
       onError = { uiState.tryEmit(key, HomeUiState.Error(it)) },
     )
   }.stateIn(
@@ -52,7 +54,7 @@ class HomeViewModel @Inject constructor(
   )
 
   fun fetchNextPokemonList() {
-    if (uiState.value != HomeUiState.Loading) {
+    if (uiState.value != HomeUiState.Loading && !isLastPageReached) {
       pokemonFetchingIndex.value++
     }
   }