In.comparision.to.RxSwift.flatMapFirst.alternatives.for.combine.swift

In.comparision.to.RxSwift.flatMapFirst.alternatives.for.combine.swift

//  Created by dsxsxsxs on 2020/09/15.
//  Copyright © 2020 me.dsxsxsxs.rx.playground. All rights reserved.
//
import RxSwift
import RxRelay
import RxTest
import XCTest
import Combine
@testable import RxPlayground

class FlatMapTest: XCTestCase {
    struct EventAndTimestamp: Equatable {
        let time: Int
        let event: Int
    }

    func testRxFlatMapFirstWithTrigger() {
       func delay5<T>(_ t: T) -> Single<T> {
           Single.just(t)
               .delay(.seconds(5), scheduler: scheduler)
       }

       let scheduler = TestScheduler(initialClock: 0)
       let trigger = PublishRelay<Int>()
       let first = trigger.flatMapFirst { delay5($0) }

       let resultObserver = scheduler.createObserver(Int.self)
       _ = first.bind(to: resultObserver)
       scheduler.scheduleAt(0, action: { trigger.accept(0) })
       scheduler.scheduleAt(1, action: { trigger.accept(1) })
       scheduler.scheduleAt(2, action: { trigger.accept(2) })
       scheduler.scheduleAt(8, action: { trigger.accept(3) })

       scheduler.start()

        XCTAssertEqual(resultObserver.events, [
           .next(5, 0),
           .next(13, 3)
       ])
    }


    func testCombineFlatMapMax1WithTrigger() {
        let scheduler = DispatchQueue(label: "abcd")
        func delay5<T>(_ t: T) -> AnyPublisher<T, Never> {
            Just(t)
                .delay(for: .seconds(5), scheduler: scheduler)
                .eraseToAnyPublisher()
        }
        let expectation = XCTestExpectation()
        let trigger = PassthroughSubject<Int, Never>()
        let now = DispatchTime.now()
        var cancellables: [AnyCancellable] = []

        var collectedEventAndTimestamp: [EventAndTimestamp] = []
        let first = trigger
            .flatMap(maxPublishers: .max(1)) { delay5($0) }
        first.sink(receiveCompletion: { _ in
        }) {
            collectedEventAndTimestamp.append(.init(time: Int((DispatchTime.now().rawValue - now.rawValue) / 1000000000), event: $0))
        }
        .store(in: &cancellables)
        scheduler.asyncAfter(deadline: now) { trigger.send(0) }
        scheduler.asyncAfter(deadline: now + .seconds(1)) { trigger.send(1) }
        scheduler.asyncAfter(deadline: now + .seconds(2)) { trigger.send(2) }
        scheduler.asyncAfter(deadline: now + .seconds(8)) { trigger.send(3) }
        scheduler.asyncAfter(deadline: now + .seconds(15)) {
            XCTAssertEqual(collectedEventAndTimestamp, [
                .init(time: 5, event: 0),
                .init(time: 13, event: 3)
            ])
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 100)
    }

    func testRxFlatMapFirstWithInterval() {
        func delay5<T>(_ t: T) -> Single<T> {
            Single.just(t)
                .delay(.seconds(5), scheduler: scheduler)
        }

        let scheduler = TestScheduler(initialClock: 0)
        let first = Observable<Int>.interval(.seconds(1), scheduler: scheduler)
            .take(10)
            .flatMapFirst { delay5($0) }

        let resultObserver = scheduler.createObserver(Int.self)
        first.bind(to: resultObserver)
        scheduler.start()

        XCTAssertEqual(resultObserver.events,[
            .next(6, 0),
            .next(12, 6),
            .completed(13)
        ])
    }

    func testCombineFlatMapMax1WithInterval() {
        let scheduler = DispatchQueue(label: "abcd")
        func delay5<T>(_ t: T) -> AnyPublisher<T, Never> {
            Just(t)
                .delay(for: .seconds(5), scheduler: scheduler)
                .eraseToAnyPublisher()
        }
        let expectation = XCTestExpectation()
        let now = DispatchTime.now()
        var cancellables: [AnyCancellable] = []
        let timer = Timer.TimerPublisher(interval: 1, runLoop: .main, mode: .default)
        let first = timer
            .zip((0..<10).publisher)
            .map { $1 }
            .prefix(10)
            .flatMap(maxPublishers: .max(1)) { delay5(Int($0)) }

        var collectedEventAndTimestamp: [EventAndTimestamp] = []
        timer.connect().store(in: &cancellables)
        first.sink(receiveCompletion: { _ in
        }) {
            collectedEventAndTimestamp.append(.init(time: Int((DispatchTime.now().rawValue - now.rawValue) / 1000000000), event: $0))
        }
        .store(in: &cancellables)

        scheduler.asyncAfter(deadline: now + .seconds(15)) {
            XCTAssertEqual(collectedEventAndTimestamp, [
                .init(time: 6, event: 0),
                .init(time: 12, event: 1)
            ])
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 50)
    }

    func testCombineFlatMapBufferWithTrigger() {
        let scheduler = DispatchQueue(label: "abcd")
        func delay5<T>(_ t: T) -> AnyPublisher<T, Never> {
            Just(t)
                .delay(for: .seconds(5), scheduler: scheduler)
                .eraseToAnyPublisher()
        }
        let expectation = XCTestExpectation()
        let trigger = PassthroughSubject<Int, Never>()
        let now = DispatchTime.now()
        var cancellables: [AnyCancellable] = []

        var collectedEventAndTimestamp: [EventAndTimestamp] = []
        let first = trigger
            // buffer + flatMap不管用，做不出期待的效果
            .buffer(size: 1, prefetch: .byRequest, whenFull: .dropNewest)
            .flatMap { delay5($0) }

        first.sink(receiveCompletion: { _ in
        }) {
            collectedEventAndTimestamp.append(.init(time: Int((DispatchTime.now().rawValue - now.rawValue) / 1000000000), event: $0))
        }
        .store(in: &cancellables)
        scheduler.asyncAfter(deadline: now) { trigger.send(0) }
        scheduler.asyncAfter(deadline: now + .seconds(1)) { trigger.send(1) }
        scheduler.asyncAfter(deadline: now + .seconds(2)) { trigger.send(2) }
        scheduler.asyncAfter(deadline: now + .seconds(8)) { trigger.send(3) }
        scheduler.asyncAfter(deadline: now + .seconds(15)) {
            // 這個test會fail
            XCTAssertEqual(collectedEventAndTimestamp, [
                .init(time: 5, event: 0),
                .init(time: 13, event: 3)
            ])
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 100)
    }
    
}