Revised for updating count based on response

GetListUseCase-Variable Page Size.swift

protocol GetListRepository {
    func get(uniqueId: String, startingAt offset: Int, limit: Int) -> Single<List>
}

struct GetListUseCase {
    enum Result {
        case success(List)
        case failure(Error, Int)
    }

    private let repository: GetListRepository
    private let currentPage = Variable<Int>(0)
    private let pageSize = 24
    private let uniqueId: String

    init(uniqueId: String, repository: GetListRepository) {
        self.uniqueId = uniqueId
        self.repository = repository
    }

    func getList(with nextPageTrigger: Observable<Void>) -> Observable<Result> {
        return nextPageTrigger
                .withLatestFrom(currentPage.asObservable())
                .flatMap(getPageStartingAt)
    }

    private func pageIndex(at offset: Int) -> Int {
        return offset / pageSize
    }

    private func getPageStartingAt(_ offset: Int) -> Observable<Result> {
        let currentPageIndex = self.currentPage.value
        return repository.get(uniqueId: uniqueId, startingAt: offset, limit: pageSize)
                         .do(onNext: { list in
                            self.currentPage.value = self.pageIndex(at: list.items.count)
                         })
                         .map(Result.success)
                         .catchError {
                             .just(Result.failure($0, self.currentPage.value)) }
                         .asObservable()
    }
}