Repeater.swift

import Foundation


typealias VoidVoid = () -> ()


protocol Repeating {

    func startRepeating(withIntervalInSeconds: TimeInterval)
    func stopRepeating()

}


/// Doesn't wait for the block to finish
class ImpatientRepeater: Repeating {

    required init(withBlock block: @escaping VoidVoid) {
        self.block = block
    }
    private let block: VoidVoid

    func startRepeating(withIntervalInSeconds timeInterval: TimeInterval) {
        self.stopRepeating()
        self.executeBlock()
        self.timer = Timer.scheduledTimer(timeInterval: timeInterval,
                                          target: self,
                                          selector: #selector(self.executeBlock),
                                          userInfo: nil,
                                          repeats: true)
    }

    @objc func executeBlock() {
        self.block()
    }

    func stopRepeating() {
        if timer != nil {
            timer?.invalidate()
            timer = nil
        }
    }

    private var timer: Timer?

}


/// Waits for the block to finish
class PatientRepeater: Repeating {

    /// Block argument is a closure that accepts a completion handler as an argument,
    /// calls it once it is done and passes true if it wants to be called again after
    /// the defined time interval (usually that's when the block was successful) or
    /// false if it wants to be called again immediatelly (usually when the block failed).
    required init(withBlock block: @escaping (@escaping (Bool) -> Void) -> Void) {
        self.block = block
    }
    private let block: (@escaping (Bool) -> Void) -> Void
    private let defaultTimeInterval: TimeInterval = 10

    func startRepeating(withIntervalInSeconds timeInterval: TimeInterval) {
        stopRepeating()
        self.timeInterval = timeInterval
        isRepeating = true
        executeBlock()
    }

    @objc func executeBlock() {
        self.block { shouldWaitToRepeat in
            if shouldWaitToRepeat {
                if self.isRepeating {
                    self.timer = Timer.scheduledTimer(timeInterval: self.timeInterval ?? self.defaultTimeInterval,
                                                      target: self,
                                                      selector: #selector(self.executeBlock),
                                                      userInfo: nil,
                                                      repeats: false)
                }
            } else {
                self.executeBlock()
            }
        }
    }

    func stopRepeating() {
        isRepeating = false
        timer?.invalidate()
    }

    private var isRepeating: Bool = false
    private var timeInterval: TimeInterval?
    private var timer: Timer?

}