//
//  SeekEventProducer.swift
//  AudioPlayer
//
//  Created by Kevin DELANNOY on 2016-10-27.
//  Copyright © 2016 Kevin Delannoy. All rights reserved.
//

import Foundation

private extension Selector {
    /// The selector to call when the timer ticks.
    static let timerTicked = #selector(SeekEventProducer.timerTicked(_:))
}

/// A `SeekEventProducer` generates `SeekEvent`s when it's time to seek on the stream.
class SeekEventProducer: NSObject, EventProducer {
    /// `SeekEvent` is an event generated by `SeekEventProducer`.
    ///
    /// - seekBackward: The event describes a seek backward in time.
    /// - seekForward: The event describes a seek forward in time.
    enum SeekEvent: Event {
        case seekBackward
        case seekForward
    }

    /// The timer used to generate events.
    private var timer: Timer?

    /// The listener that will be alerted a new event occured.
    weak var eventListener: EventListener?

    /// A boolean value indicating whether we're currently producing events or not.
    private var listening = false

    /// The delay to wait before cancelling last retry and retrying. Default value is 10 seconds.
    var intervalBetweenEvents = TimeInterval(10)

    /// A boolean value indicating whether the producer should generate backward or forward events.
    var isBackward = false


    /// Stops producing events on deinitialization.
    deinit {
        stopProducingEvents()
    }

    /// Starts listening to the player events.
    func startProducingEvents() {
        guard !listening else {
            return
        }

        //Creates a new timer for next retry
        restartTimer()

        //Saving that we're currently listening
        listening = true
    }

    /// Stops listening to the player events.
    func stopProducingEvents() {
        guard listening else {
            return
        }

        timer?.invalidate()
        timer = nil

        //Saving that we're not listening anymore
        listening = false
    }

    /// Stops the current timer if any and restart a new one.
    private func restartTimer() {
        timer?.invalidate()
        timer = Timer.scheduledTimer(
            timeInterval: intervalBetweenEvents,
            target: self,
            selector: .timerTicked,
            userInfo: nil,
            repeats: false)
    }

    /// The retry timer ticked.
    ///
    /// - Parameter _: The timer.
    @objc fileprivate func timerTicked(_: AnyObject) {
        eventListener?.onEvent(isBackward ? SeekEvent.seekBackward : .seekForward, generetedBy: self)
        restartTimer()
    }
}