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//
//  FollowUserViewModel.swift
//  YourFavoriteInstruments
//
//  Created by Dean Silfen on 2/2/19.
//  Copyright © 2019 Dean Silfen. All rights reserved.
//

import RxSwift
import RxCocoa

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final class FollowUserViewModel {
  // same properties as above
  init(
    networkHandler: FollowNetworkHandler, 
    scheduler: SchedulerType // inject a scheduler type to the initializer
  ) {
    followSubject
      .observeOn(scheduler)
      // transformation 
      .disposed(by: disposeBag)

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class FollowerViewModelTest: XCTestCase {
  // retain subscriptions while testing
  let disposeBag = DisposeBag()
  
  func testFollowersUpdate() {
    let testFollower = User()
    let mockNetworking = FollowerNetworkingMock(
    mockFollowers: [testFollower], 
      followResponse: .success
    )

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class FollowerViewModelTest: XCTestCase {
  let disposeBag = DisposeBag()
  func testFollowersUpdate() {
    let testFollower = User()
    let mockNetworking = FollowerNetworkingMock(mockFollowers: [testFollower])
    // Create a scheduler that starts at 0
    let scheduler = TestScheduler(initialClock: 0)
    let viewModel = FollowUserViewModel(networkHandler: mockNetworking, scheduler: scheduler)
    let testCountObserver = scheduler.createTestObserver(Int.self)
    let testLatestFollowObserver = scheduler.createTestObserver(User.self)

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/// Any old user class
class User { … }

/// Response enum to notify us about a success or failure
enum Response {
  case success
  case fail(Error)
}

/// Types that implement this protocol 

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struct FollowerNetworkingMock: FollowNetworkHandler {
  let mockFollowers: [User]
  let followResponse: Response
  func follow(user: User) -> Observable<Response> {
    return .just(followResponse)
  }
  func followers() -> Observable<[User]> {
    return .just(mockFollowers)
  }
}

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func simpleCombineStreams(
  resource: Observable<Bool>, 
  buttonTap: Observable<Void>
) -> Observable<Bool> {
  return buttonTap
    .withLatestFrom(resource)
}

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func waitForResourceAndButtonTap(
  resource: Observable<Bool>, 
  buttonTap: Observable<Void>
) -> Observable<Bool> {
  let emitOnlyAfterResourceHasArrived = Observable
    .combineLatest(
      buttonTap,
      resource.take(1)
  )

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enum TrainLine { … }
enum TrainStation { … }
protocol TrainNetworkHandler {
  func departureTime(forLine: TrainLine, departingFrom: TrainStation) -> Observable<Date>
}

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class TrainDepartureService {

  func departureTimes(forLine: TrainLine, departingFrom: TrainStation) -> Observable<Date> {
    return Observable<TimeInterval>.timer(0, period: 60, scheduler: scheduler)
      .flatMapLatest { _ -> Observable<Date> in
        network.departureTime(forLine: forLine, departingFrom: departingFrom)
      }
  }

  private let scheduler: SchedulerType