//
// Copyright 2017 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

/**
 * As of iOS10, the timer API's take a block, which makes it easy to reference weak self in Swift. This class offers a
 * similar API that works pre iOS10.
 *
 * Solution modified from
 * http://stackoverflow.com/questions/16821736/weak-reference-to-nstimer-target-to-prevent-retain-cycle/41003985#41003985
 */
public final class WeakTimer {

    private weak var timer: Timer?
    private weak var target: AnyObject?
    private let action: (Timer) -> Void

    private init(timeInterval: TimeInterval, target: AnyObject, userInfo: Any?, repeats: Bool, action: @escaping (Timer) -> Void) {
        self.target = target
        self.action = action
        self.timer = Timer.scheduledTimer(
            timeInterval: timeInterval,
            target: self,
            selector: #selector(fire),
            userInfo: userInfo,
            repeats: repeats,
        )
    }

    deinit {
        timer?.invalidate()
    }

    @objc
    public class func scheduledTimer(timeInterval: TimeInterval, target: AnyObject, userInfo: Any?, repeats: Bool, action: @escaping (Timer) -> Void) -> Timer {
        return WeakTimer(
            timeInterval: timeInterval,
            target: target,
            userInfo: userInfo,
            repeats: repeats,
            action: action,
        ).timer!
    }

    @objc
    public func fire(timer: Timer) {
        if target != nil {
            action(timer)
        } else {
            timer.invalidate()
        }
    }
}