This file is responsible for handling network request using Retrofit and pass result with RxJava Observables

RemoteDataSource.kt

open class RemoteDataSource private constructor() : DataSource {

    private val service by lazy {
        RetrofitService.create()
    }


    companion object {
        private var INSTANCE: RemoteDataSource? = null


        fun getInstance(): RemoteDataSource {
            if (INSTANCE == null) {
                INSTANCE = RemoteDataSource()
            }
            return INSTANCE!!

        }
    }

   //... some other methods
  
    override fun authorize(credentials: Credentials): Flowable<String> {
        return service.authenticate(credentials.email!!, credentials.password!!).map { it.token }
    }

    override fun getLayerIdentityToken(identityTokenBody: RetrofitService.IdentityTokenBody): Flowable<String> {
        return service.getIdentityToken(identityTokenBody)
                .map { identityToken -> identityToken.identityToken }
    }

    override fun getConversationId(): Flowable<Optional<String>> {
        return service.getConversationId()
                .map { conversationId -> conversationId.conversationId.toOptional() }
    }

    override fun selectWidget(model: Model, id: Int): Completable {
        return when (model) {
            Model.FLIGHT -> service.selectFlightWidget(id)
            Model.HOTEL -> service.selectHotelWidget(id)
            Model.CAR -> service.selectCarWidget(id)
            Model.TRAIN -> service.selectTrainWidget(id)
        }
    }

    override fun selectWidgetWithCF(model: Model, optionId: Int, taskId: Int, state: String): Completable {
        val selectCfBody = SelectCFBody(optionId, taskId, state)
        return when (model) {
            Model.FLIGHT -> service.selectFlightWidgetWithCF(selectCfBody)
            Model.HOTEL -> service.selectHotelWidgetWithCF(selectCfBody)
            Model.CAR -> service.selectCarWidgetWithCF(selectCfBody)
            Model.TRAIN -> service.selectTrainWidgetWithCF(selectCfBody)
        }
    }

    override fun resetPassword(email: String): Completable {
        return service.resetPassword(RetrofitService.Email(email))
    }

    override fun saveProfile(profile: Profile): Completable {
        return service.saveProfile(profile)
    }

    override fun getSettings(): Single<Optional<UserSettings>> {
        return service.getSettings().map { it.toOptional() }
    }

    override fun saveAccount(account: UserAccount): Completable {
        return service.saveAccount(account)
    }

    override fun changePassword(newPassword: RetrofitService.NewPassword): Completable {
        return service.changePassword(newPassword)
    }

    override fun saveBusinessAddress(address: Address): Completable {
        return service.saveBusinessAddress(address)
    }
  
   //... some other methods
}