Cancellation Token about promises HOT 6 CLOSED

     func testPromise() -> Promise<[Icon]> {
        return Promise<[Icon]>(on: .global(qos: .userInitiated)) {
            return self.loadHtml()
                .then({ (html) -> Promise<[URL]> in
                    return self.parseHtml(with: html)
                })
                .then({ (urls) -> Promise<[Icon]> in
                    return Promises.any([
                        self.faviconByUrl(urls: urls),
                        Promises.all([
                            self.faviconSmall(),
                            self.faviconAppleTouch()
                        ])
                    ])
                    .then({ (result: [Maybe<[Icon]>]) -> Promise<[Icon]> in
                        fatalError() // do some transformations here ...
                    })
                })
        }
    }
    
    func loadHtml() -> Promise<String> {
        fatalError()
    }
    
    func faviconAppleTouch() -> Promise<Icon> {
        fatalError()
    }
    
    func faviconSmall() -> Promise<Icon> {
        fatalError()
    }
    
    func faviconByUrl(urls: [URL]) -> Promise<[Icon]> {
        return Promises.all(urls.map { self.download(url: $0) })
    }
    
    func parseHtml(with: String) -> Promise<[URL]> {
        fatalError()
    }
    
    func download(url: URL) -> Promise<Icon> {
        fatalError()
    }

func testIntegration2() {
        let token = CancellationToken()
        
        self.testPromise(token: token)
            .then { (icons) in
                // on success
            }
            .catch { (error) in
                // on fail or cancel
            }
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            token.cancel() // simulate cancel
        }
    }
    
    func testPromise(token: CancellationToken? = nil) -> Promise<[Icon]> {
        return Promise<[Icon]>(on: .global(qos: .userInitiated)) {
            return self.loadHtml(token: token)
                .then({ (html) -> Promise<[URL]> in
                    return self.parseHtml(with: html)
                })
                .then({ (urls) -> Promise<[Icon]> in
                    return Promises.any([
                        self.faviconByUrl(urls: urls, token: token),
                        Promises.all([
                            self.faviconSmall(token: token),
                            self.faviconAppleTouch(token: token)
                        ])
                    ])
                    .then({ (result: [Maybe<[Icon]>]) -> Promise<[Icon]> in
                        fatalError() // do some transformations here ...
                    })
                })
            

        }
    }
    
    func loadHtml(token: CancellationToken? = nil) -> Promise<String> {
        fatalError()
    }
    
    func faviconAppleTouch(token: CancellationToken? = nil) -> Promise<Icon> {
        fatalError()
    }
    
    func faviconSmall(token: CancellationToken? = nil) -> Promise<Icon> {
        fatalError()
    }
    
    func faviconByUrl(urls: [URL], token: CancellationToken? = nil) -> Promise<[Icon]> {
        return Promises.all(urls.map { self.download(url: $0) })
    }
    
    func parseHtml(with: String) -> Promise<[URL]> {
        fatalError()
    }
    
    func download(url: URL, token: CancellationToken? = nil) -> Promise<Icon> {
        return Promise {
            let request = URLRequest(url: url)
            let task = URLSession(configuration: .ephemeral).dataTask(with: request) { data, response, error in
                // fulfill or resolve
            }
            
            try token?.onCancel {
                task.cancel()
            }
            
            task.resume()
        }
    }