DeepPressGestureRecognizer.swift

//
//  DeepPressGestureRecognizer.swift
//  DeepPressGestureRecognizer
//
//  Created by SIMON_NON_ADMIN on 03/10/2015.
//  Copyright © 2015 Simon Gladman. All rights reserved.
//
//  Thanks to Alaric Cole - bridging header replaced by proper import :)

import AudioToolbox
import UIKit.UIGestureRecognizerSubclass

// MARK: GestureRecognizer

@available(iOS 9.0, *)
class DeepPressGestureRecognizer: UIGestureRecognizer
{
    var vibrateOnDeepPress = false
    let threshold: CGFloat
    
    private let pulse = PulseLayer()
    private var deepPressed: Bool = false
    
    required init(target: AnyObject?, action: Selector, threshold: CGFloat)
    {
        self.threshold = threshold
        
        super.init(target: target, action: action)
    }
    
    override func touchesBegan(_  touches: Set<UITouch>, with event: UIEvent)
    {
        if let touch = touches.first
        {
            handleTouch(touch: touch)
        }
    }

    override func  touchesMoved(_ touches: Set<UITouch>, with event: UIEvent)
    {
        if let touch = touches.first
        {
            handleTouch(touch: touch)
        }
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent)
    {
        super.touchesEnded(touches, with: event)
        
        state = deepPressed ? UIGestureRecognizerState.ended : UIGestureRecognizerState.failed
        
        deepPressed = false
    }
    
    private func handleTouch(touch: UITouch)
    {
        guard let view = view, touch.force != 0 && touch.maximumPossibleForce != 0 else
        {
            return
        }
        
        if !deepPressed && (touch.force / touch.maximumPossibleForce) >= threshold
        {
            view.layer.addSublayer(pulse)
            pulse.pulse(frame: CGRect(origin: CGPoint.zero, size: view.frame.size))
            
            state = UIGestureRecognizerState.began
            
            if vibrateOnDeepPress
            {
                AudioServicesPlayAlertSound(kSystemSoundID_Vibrate)
            }
            
            deepPressed = true
        }
        else if deepPressed && (touch.force / touch.maximumPossibleForce) < threshold
        {
            state = UIGestureRecognizerState.ended
            
            deepPressed = false
        }
    }
}

// MARK: DeepPressable protocol extension

protocol DeepPressable
{
    var gestureRecognizers: [UIGestureRecognizer]? {get set}
    
    func addGestureRecognizer(gestureRecognizer: UIGestureRecognizer)
    func removeGestureRecognizer(gestureRecognizer: UIGestureRecognizer)
    
    func setDeepPressAction(target: AnyObject, action: Selector)
    func removeDeepPressAction()
}

@available(iOS 9.0, *)
extension DeepPressable
{
    func setDeepPressAction(target: AnyObject, action: Selector)
    {
        let deepPressGestureRecognizer = DeepPressGestureRecognizer(target: target, action: action, threshold: 0.75)
        
        self.addGestureRecognizer(gestureRecognizer: deepPressGestureRecognizer)
    }
    
    func removeDeepPressAction()
    {
        guard let gestureRecognizers = gestureRecognizers else
        {
            return
        }
        
        for recogniser in gestureRecognizers where recogniser is DeepPressGestureRecognizer
        {
            removeGestureRecognizer(gestureRecognizer: recogniser)
        }
    }
}

// MARK: PulseLayer

// Thanks to http://jamesonquave.com/blog/fun-with-cashapelayer/

class PulseLayer: CAShapeLayer
{
    var pulseColor: CGColor = UIColor.red.cgColor
    
    func pulse(frame: CGRect)
    {
        strokeColor = pulseColor
        fillColor = nil
        
        let startPath = UIBezierPath(roundedRect: frame, cornerRadius: 5).cgPath
        let endPath = UIBezierPath(roundedRect: frame.insetBy(dx: -50, dy: -50), cornerRadius: 5).cgPath
        
        path = startPath
        lineWidth = 1
        
        let pathAnimation = CABasicAnimation(keyPath: "path")
        pathAnimation.toValue = endPath
        
        let opacityAnimation = CABasicAnimation(keyPath: "opacity")
        opacityAnimation.toValue = 0
        
        let lineWidthAnimation = CABasicAnimation(keyPath: "lineWidth")
        lineWidthAnimation.toValue = 10
        
        CATransaction.begin()
        
        CATransaction.setCompletionBlock
            {
                self.removeFromSuperlayer()
        }
        
        for animation in [pathAnimation, opacityAnimation, lineWidthAnimation]
        {
            animation.duration = 0.25
            animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
            animation.isRemovedOnCompletion = false
            animation.fillMode = kCAFillModeForwards
            
            add(animation, forKey: animation.keyPath)
        }
        
        CATransaction.commit()
    }
}