Animates a wave ripple along the top

WaveView.swift

import UIKit

// MARK: - WaveView

class WaveView: UIView {
	
	private var shapeLayer: CAShapeLayer = CAShapeLayer()
	
	// MARK: - Animation Properties
	
	/// 0 - Static
	/// 20 - Very fast
	var speed: CGFloat = 10
	
	/// Wave Height
	var frequency: CGFloat = 6.0
	
	/// Wave phase
	private var phase: CGFloat = 0.0
	
	/// Wave color
	var preferredColor: UIColor = UIColor.cyan {
		didSet {
			self.shapeLayer.fillColor = self.preferredColor.cgColor
			self.shapeLayer.strokeColor = self.preferredColor.cgColor
		}
	}
	
	// MARK: - Start Animation
	
	enum Direction {
		case right
		case left
	}
	
	func animationStart(direction: Direction, speed: Double) {
		self.preferredColor = UIColor.cyan
		self.layer.addSublayer(self.shapeLayer)
		
		if direction == .right {
			self.speed = -speed
		} else {
			self.speed = speed
		}
		
		self.startDisplayLink()
	}
	
	
	// MARK: - Display Link
	
	private weak var displayLink: CADisplayLink?
	
	private var startTime: CFTimeInterval = 0
	
	private func startDisplayLink() {
		self.startTime = CACurrentMediaTime()
		self.displayLink?.invalidate()
		
		let displayLink = CADisplayLink(target: self, selector:#selector(self.handleDisplayLink(_:)))
		displayLink.add(to: .main, forMode: .common)
		self.displayLink = displayLink
	}
	
	@objc private func handleDisplayLink(_ displayLink: CADisplayLink) {
		self.phase = (CACurrentMediaTime() - self.startTime) * self.speed
		
		self.updatePath()
	}
	
	private func stopDisplayLink() {
		self.displayLink?.invalidate()
	}
	
	
	// MARK: - Layout
	
	override func layoutSubviews() {
		super.layoutSubviews()
		
		self.shapeLayer.frame = self.bounds
		self.updatePath()
	}
	
	func updatePath() {
		let path: UIBezierPath = UIBezierPath()
		let width: CGFloat = self.bounds.width
		let height: CGFloat = self.bounds.height
		
		let mid: CGFloat = height * 0.25
		
		let waveLength: CGFloat = width / self.frequency
		let waveHeightCoef: CGFloat = self.frequency
		
		path.move(to: CGPoint(x: 0, y: self.bounds.maxY))
		path.addLine(to: CGPoint(x: 0, y: mid))
		
		for x in stride(from: 0, through: width, by: 1)
		{
			let actualX: CGFloat = x / waveLength
			let sine: CGFloat = -sin((actualX + self.phase))
			
			let y: CGFloat = waveHeightCoef * sine + mid
			path.addLine(to: CGPoint(x: x, y: y))
		}
		
		path.addLine(to: CGPoint(x: CGFloat(width), y: self.bounds.maxY))
		path.addLine(to: CGPoint(x: 0, y: self.bounds.maxY))
		
		self.shapeLayer.path = path.cgPath
	}
}