Activity 7 Step 3

DataRepository.kt

@Singleton
class DataRepository @Inject constructor(
    @ApplicationContext private val context: Context
) {
    ...
    companion object {
        private val GENERATED_TOPICS_KEY = stringPreferencesKey("generatedTopics")
        private const val TOPICS_DATASTORE = "topics_datastore"
        private const val SPLITTING_DELIMITER = "::"
    }

    private val Context.preferenceDataStore: DataStore<Preferences> by preferencesDataStore(name = TOPICS_DATASTORE)

    fun hasGeneratedTopics(): Flow<Boolean> {
        return context.preferenceDataStore.data.map { preferences ->
            preferences.contains(GENERATED_TOPICS_KEY)
        }
    }

    fun getGeneratedTopics(): Flow<List<Topic>> {
        return context.preferenceDataStore.data.map { preferences ->
            preferences[GENERATED_TOPICS_KEY]?.split(SPLITTING_DELIMITER)?.map {
                Topic(
                    name = it.trim(),
                    isGenerative = true,
                    quotes = emptyList()
                )
            } ?: emptyList()
        }
    }

    suspend fun saveGeneratedTopics(topic: List<Topic>) {
        context.preferenceDataStore.edit { preferences ->
            preferences[GENERATED_TOPICS_KEY] = topic.joinToString(SPLITTING_DELIMITER) { it.name }
        }
    }
}

MainViewModel.kt

@HiltViewModel
class MainViewModel @Inject constructor(
...
init {
    viewModelScope.launch {
        if (!dataRepository.hasGeneratedTopics().first()) {
            generateTopics()
        } else {
            dataRepository.getGeneratedTopics().collect {
                showLoading.emit(false)
                _generatedTopics.emit(it)
            }
        }
    }
}

private fun generateTopics() {
    viewModelScope.launch(Dispatchers.IO) {
        ...
        dataRepository.saveGeneratedTopics(newTopics)
    }
}