CitiesRepo

class CitiesRepository @Inject constructor(
        private val cityDao: CityDao,
        private val listsService: ListsService,
        private val schedulerProvider: SchedulerProvider
): ICitiesRepository {

    override fun cities(): Single<List<City>> {
        return citiesFromDB()
                .flatMap { cities ->
                    if (cities.isEmpty()){
                        citiesFromAPI()
                    } else {
                        Single.just(cities)
                    }
                }
    }


    private fun citiesFromDB(): Single<List<City>> {
        return cityDao.allCities()
                .subscribeOn(schedulerProvider.computation())
                .doOnSuccess { Logger.i("Received ${it.size} cities from DB") }
    }

    private fun citiesFromAPI(): Single<List<City>> {
        val mapList: (List<City>) -> List<City> = { cities ->
                cities
                .asSequence()
                .map { it.apply { name = it.name.trim() } }
                .sortedBy { it.name }
                .toList()
        }

        return listsService.cities()
            .validateResult()
            .mapResponseData()
            .map(mapList)
            .doOnSuccess { Logger.i("Received cities list from API: $it") }
            .doOnSuccess(this::saveCities)
    }

    private fun saveCities(cities: List<City>) {
        cityDao.insertCities(cities)
        repoStoredLog(cities, "cities")
    }

}