Restart.swift

//
//  Restart.swift
//
//  Created by Daniel Tartaglia on 23 Jun 2022.
//  Copyright © 2022 Daniel Tartaglia. MIT License.
//

import RxSwift

extension ObservableType {
    /**
     Repeats the source observable sequence on error when the notifier emits a next value. If the source observable
     errors and the notifier completes, it will complete the source sequence.

     - seealso: [retry operator on reactivex.io](http://reactivex.io/documentation/operators/retry.html)

     - Parameter notificationHandler: A handler that is passed an observable sequence of both errors raised by the
     source observable along with a count of previous consecutive errors and returns an observable that either
     continues, completes or errors. This behavior is then applied to the source observable.
     - Returns: An observable sequence producing the elements of the given sequence repeatedly until it terminates
     successfully or is notified to error or complete.
     */
    func restart<TriggerObservable>(when notificationHandler: @escaping (Observable<(Int, Error)>) -> TriggerObservable) -> Observable<Element>
    where TriggerObservable: ObservableType {
        let count = BehaviorSubject<Int>(value: 0)
        return self.do(
            onNext: { _ in
                count.onNext(0)
            },
            onError: { _ in
                count.onNext(try! count.value() + 1)
            }
        )
            .retry { error in
                notificationHandler(error.withLatestFrom(count) { ($1, $0) })
            }
    }
}