CountDown Timer

import UIKit

@objc public protocol TimerLabelDelegate {
    optional func countdownStarted()
    optional func countdownFinished()
}

public extension NSTimeInterval {
    var int: Int {
        return Int(self)
    }
}

public class TimerLabel: UILabel {

    public typealias CountdownCompletion = () -> ()?
    public typealias CountdownExecution = () -> ()
    private let defaultFireInterval = 1.0
//    private let date1970 = NSDate(timeIntervalSince1970: 0)

    public var dateFormatter: NSDateFormatter {
        let df = NSDateFormatter()
        df.locale = NSLocale.currentLocale()
        df.timeZone = NSTimeZone(name: "GMT")
        df.dateFormat = timeFormat
        return df
    }

    public var timeCounted: NSTimeInterval {
        let timeCounted = NSDate().timeIntervalSinceDate(fromDate)
        return round(timeCounted < 0 ? 0 : timeCounted)
    }

    public var timeRemaining: NSTimeInterval {
        return round(currentTime) - timeCounted
    }

    public var isPaused: Bool {
        return paused
    }

    public var isCounting: Bool {
        return counting
    }

    public var isFinished: Bool {
        return finished
    }

    public weak var timerLabelDelegate: TimerLabelDelegate?

    public var timeFormat = "HH:mm:ss"
    public var thens = [NSTimeInterval: CountdownExecution]()
    public var countdownAttributedText: CountdownAttributedText! {
        didSet {
            range = (countdownAttributedText.text as NSString).rangeOfString(countdownAttributedText.replacement)
        }
    }

    private var completion: CountdownCompletion?
    private var fromDate: NSDate = NSDate()
    private var currentDate: NSDate = NSDate()
    private var currentTime: NSTimeInterval = 0
    private var diffDate: NSDate!
    private var targetTime: NSTimeInterval = 0
    private var pausedDate: NSDate!
    private var range: NSRange!
    private var timer: NSTimer!

    private var counting: Bool = false
    private var endOfTimer: Bool {
        return timeCounted >= currentTime
    }
    private var finished: Bool = false {
        didSet {
            if finished {
                paused = false
                counting = false
            }
        }
    }
    private var paused: Bool = false

    // MARK: - Initialize
    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

    }

    override init(frame: CGRect) {
        super.init(frame: frame)

    }

    public convenience init(frame: CGRect, minutes: NSTimeInterval) {
        self.init(frame: frame)
        setCountDownTime(minutes)
    }

    public convenience init(frame: CGRect, date: NSDate) {
        self.init(frame: frame)
        setCountDownDate(date)
    }

    public convenience init(frame: CGRect, fromDate: NSDate, targetDate: NSDate) {
        self.init(frame: frame)
        setCountDownDate(fromDate, targetDate: targetDate)
    }

    deinit {
        dispose()
    }

    // MARK: - Setter Methods
    public func setCountDownTime(minutes: NSTimeInterval) {
        setCountDownTime(NSDate(), minutes: minutes)
    }

    public func setCountDownTime(fromDate: NSDate, minutes: NSTimeInterval) {
        self.fromDate = fromDate

        targetTime = minutes
        currentTime = minutes
        diffDate = fromDate.dateByAddingTimeInterval(minutes)

        updateLabel()
    }

    public func setCountDownDate(targetDate: NSDate) {
        setCountDownDate(NSDate(), targetDate: targetDate)
    }

    public func setCountDownDate(fromDate: NSDate, targetDate: NSDate) {
        self.fromDate = fromDate

        targetTime = targetDate.timeIntervalSinceDate(fromDate)
        currentTime = targetDate.timeIntervalSinceDate(fromDate)
        diffDate = fromDate.dateByAddingTimeInterval(targetTime)

        updateLabel()
    }

    // MARK: - Update
    func updateLabel() {

        // then function execute if needed
        thens.forEach { k, v in
            if k.int == timeRemaining.int {
                v()
                thens[k] = nil
            }
        }

        // update text
        updateText()

        // if end of timer
        if endOfTimer {
            text = dateFormatter.stringFromDate(fromDate.dateByAddingTimeInterval(0))
    timerLabelDelegate?.countdownFinished?()
    dispose()
    completion?()
}
    }
}

// MARK: - Public
public extension TimerLabel {
    func start(completion: ( () -> () )? = nil) {
if !isPaused {
    // current date should be setted at the time of the counter's starting, or the time will be wrong (just a few seconds) after the first time of pausing.
    currentDate = NSDate()
}

// pause status check
updatePauseStatusIfNeeded()

// create timer
updateTimer()

// fire!
timer.fire()

// set completion if needed
completion?()

// set delegate
timerLabelDelegate?.countdownStarted?()
    }

}

// MARK: - private
private extension TimerLabel {

    func updateText() {
        guard diffDate != nil else { return }

        // if time is before start
        let formattedText = timeCounted < 0
            ? dateFormatter.stringFromDate(fromDate.dateByAddingTimeInterval(0))
            : dateFormatter.stringFromDate(diffDate.dateByAddingTimeInterval(round(timeCounted * -1)))

        if let countdownAttributedText = countdownAttributedText {
            let attrTextInRange = NSAttributedString(string: formattedText, attributes: countdownAttributedText.attributes)
            let attributedString = NSMutableAttributedString(string: countdownAttributedText.text)
            attributedString.replaceCharactersInRange(range, withAttributedString: attrTextInRange)

            attributedText = attributedString
            text = attributedString.string
        } else {
            text = formattedText
        }
        setNeedsDisplay()
    }

    func updatePauseStatusIfNeeded() {
        guard paused else {
            return
        }
        // change date
        let pastedTime = pausedDate.timeIntervalSinceDate(currentDate)
        currentDate = NSDate().dateByAddingTimeInterval(-pastedTime)
        fromDate = currentDate

        // reset pause
        pausedDate = nil
        paused = false
    }

    func updateTimer() {
        disposeTimer()

        // create
        timer = NSTimer.scheduledTimerWithTimeInterval(defaultFireInterval,
                                                       target: self,
                                                       selector: #selector(updateLabel),
                                                       userInfo: nil,
                                                       repeats: true)

        // register to NSrunloop
        NSRunLoop.currentRunLoop().addTimer(timer, forMode: NSRunLoopCommonModes)
        counting = true
    }

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

    func dispose() {
        // reset
        pausedDate = nil

        // invalidate timer
        disposeTimer()

        // stop counting
        finished = true
    }
}

public class CountdownAttributedText: NSObject {
    private let text: String
    private let replacement: String
    private let attributes: [String: AnyObject]?

    public init(text: String, replacement: String, attributes: [String: AnyObject]? = nil) {
        self.text = text
        self.replacement = replacement
        self.attributes = attributes
    }
}