public class GTForceTouchGestureRecognizer: UIGestureRecognizer {

    internal var deepPressedAt: TimeInterval = 0
    internal var gestureParameters: (target: AnyObject?, action: Selector)
    internal var hardTriggerMinTime: TimeInterval
    internal let feedbackGenerator = UIImpactFeedbackGenerator.init(style: .medium)
    internal let threshold: CGFloat

    internal var deepPressed: Bool = false {
        didSet {
            guard deepPressed, !oldValue else {
                return
            }
            deepPressedAt = NSDate.timeIntervalSinceReferenceDate
        }
    }

    public override var state: UIGestureRecognizer.State {
        didSet {
            guard oldValue != state else {
                return
            }
            switch state {
            case .began:
                feedbackGenerator.prepare()
            case .ended:
                feedbackGenerator.impactOccurred()
                _ = gestureParameters.target?.perform(gestureParameters.action, with: self)
            default:
                return
            }
        }
    }

    required public init(target: AnyObject?, action: Selector, threshold: CGFloat = 0.75, hardTriggerMinTime: TimeInterval = 0.5) {
        self.gestureParameters = (target, action)
        self.threshold = threshold
        self.hardTriggerMinTime = hardTriggerMinTime
        super.init(target: nil, action: nil)
    }

    override public func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        handleTouch(touches.first)
    }

    override public func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent) {
        handleTouch(touches.first)
    }

    override public func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
        state = deepPressed ? UIGestureRecognizer.State.ended : UIGestureRecognizer.State.failed
        deepPressed = false
        super.touchesEnded(touches, with: event)
    }

    internal func handleTouch(_ touch: UITouch?) {
        guard view != nil, let touch = touch, touch.force != 0 && touch.maximumPossibleForce != 0 else {
            return
        }
        let forcePercentage = touch.force / touch.maximumPossibleForce
        if deepPressed && forcePercentage <= 0 {
            state = UIGestureRecognizer.State.ended
            return
        }
        handleForceTouch(with: forcePercentage)
    }

    private func handleForceTouch(with forcePercentage: CGFloat) {
        let currentTime = NSDate.timeIntervalSinceReferenceDate
        if !deepPressed && forcePercentage >= threshold {
            deepPressed = true
            state = UIGestureRecognizer.State.began
            return
        }
        if deepPressed && currentTime - deepPressedAt > hardTriggerMinTime && forcePercentage == 1.0 {
            state = UIGestureRecognizer.State.ended
        }
    }
}