currency firebase database model

CurrencyFirebaseDB.swift

protocol CurrencyFirebaseDB {
    var ref: DatabaseReference { get }
    func getExchangeRate() -> Observable<[CurrencyExchangeRate]>
}

extension CurrencyFirebaseDB {
    var ref: DatabaseReference {
        return Service.shared.container.resolve(DatabaseReference.self, name: Service.RegisterationName.firebaseCurrencyExchageRate.rawValue)!
    }
    
    var loadData: Observable<DataSnapshot> {
        return Service.shared.container.resolve(Observable<DataSnapshot>.self, name: Service.RegisterationName.firebaseCurrencyExchageRate.rawValue)!
    }
    
    func deleteRef() {
        self.ref.removeValue()
    }
    
    func getExchangeRate() -> Observable<[CurrencyExchangeRate]> {
        let remoteApi = Api.getCurrencyExchangeRate(firebaseSaveBlock: { data in
            log.debug("remote api")
            if let dict = try? JSONDecoder().decode(ExchangeRate.self, from: data).convertDict() {
                log.debug("save firebase database")
                self.ref.setValue(dict, withCompletionBlock: { (_,_) in })
            }
        }).asObservable()
        let firebaseApi = self.loadData.map{ snapshot in
            log.debug("get firebase database")
            var rates = [CurrencyExchangeRate]()
            if let value = snapshot.value, let exchangeRate = try? FirebaseDecoder().decode(ExchangeRate.self, from: value) {
                rates = exchangeRate.convertCurrencyExchangeRate()
                CurrencyExchangeRateLocalApi.saveExchangeRate(rates: rates)
            }
            return rates
        }.ifEmpty(switchTo: remoteApi)
        return CurrencyExchangeRateLocalApi.getExchangeRate().do(onNext: { rates in
            log.debug("getting local database")
            if let time = rates.first?.updatedAt, Date(timeIntervalSince1970: time).moreThenOneDay() {
                log.debug("local db: more then one day")
                _ = firebaseApi.subscribe()
            }
        }).ifEmpty(switchTo: firebaseApi).observeOn(MainScheduler.instance)
    }
}