CircularProgressBar.swift

//
//  CircularProgressBar.swift
//
//  Created by Joshua Asbury on 29/9/18.
//  Copyright © 2018 Joshua Asbury. All rights reserved.
//

import UIKit

@IBDesignable public class CircularProgressBar: UIView {
    
    // MARK: Properties
    
    @IBInspectable public var lineWidth: CGFloat = 6 {
        didSet {
            trackLayer.lineWidth = lineWidth
            progressLayer.lineWidth = lineWidth
        }
    }
    @IBInspectable public var trackTintColor: UIColor = .lightGray {
        didSet {
            trackLayer.strokeColor = trackTintColor.cgColor
        }
    }
    @IBInspectable public var progressTintColor: UIColor = .red {
        didSet {
            progressLayer.strokeColor = progressTintColor.cgColor
        }
    }
    public var animationDuration: Double = 0.4
    
    private let trackLayer = CAShapeLayer()
    private let progressLayer = CAShapeLayer()
    
    // MARK: UIView overrides
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    
    override public func prepareForInterfaceBuilder() {
        commonInit()
    }
    
    private func commonInit() {
        let diameter = min(self.bounds.width, self.bounds.height) - lineWidth
        
        // configure track layer
        trackLayer.path = trackPath(withDiameter: diameter).cgPath
        
        trackLayer.lineWidth = lineWidth
        trackLayer.fillColor = nil
        trackLayer.strokeColor = trackTintColor.cgColor
        
        self.layer.addSublayer(trackLayer)
        
        // configure progress layer
        progressLayer.path = progressPath(withDiameter: diameter).cgPath
        
        progressLayer.lineWidth = lineWidth
        progressLayer.fillColor = nil
        progressLayer.strokeColor = progressTintColor.cgColor
        progressLayer.strokeEnd = 0
        
        self.layer.addSublayer(progressLayer)
    }
    
    private func trackPath(withDiameter diameter: CGFloat) -> UIBezierPath {
        let x = (self.bounds.width - diameter) / 2
        let y = (self.bounds.height - diameter) / 2
        return UIBezierPath(ovalIn: CGRect(x: x, y: y, width: diameter, height: diameter))
    }
    
    private func progressPath(withDiameter diameter: CGFloat) -> UIBezierPath {
        let radius = diameter / 2
        let x = ((self.bounds.width - diameter) / 2) + radius
        let y = ((self.bounds.height - diameter) / 2) + radius
        let startAngle = -CGFloat.pi / 2
        let endAngle = 2 * CGFloat.pi + startAngle
        return UIBezierPath(arcCenter: CGPoint(x: x, y: y), radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
    }
    
    public func setProgress(_ value: CGFloat, animated: Bool) {
        let progress = max(min(value, 1.0), 0.0)
        
        if animated {
            let animation = CABasicAnimation(keyPath: #keyPath(CAShapeLayer.strokeEnd))
            animation.duration = animationDuration
            animation.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
            
            animation.toValue = progress
            
            // ensure the animation isn't reverted once complete
            animation.fillMode = .forwards
            animation.isRemovedOnCompletion = false
            
            progressLayer.add(animation, forKey: nil)
        }
    }
    
}