ProgressCircle.swift

//
//  ProgressCircle.swift
//  Quicker
//
//  Created by Danis Ziganshin on 13/06/2017.
//  Copyright © 2017 ZedPlus. All rights reserved.
//

import Foundation
import UIKit

class ProgressCircle: UIView {
    
    private let lineWidth: CGFloat = 4
    private var segments = [Int: UIColor]()
    private let total: Int
    
    init(frame: CGRect, total: Int) {
        self.total = total
        for i in 0..<total {
            segments[i] = UIColor.appGrey
        }
        super.init(frame: frame)
        backgroundColor = UIColor.clear
    }
    
    @available(*, unavailable)
    override init(frame: CGRect) {
        fatalError("init(frame:) has not been implemented")
    }
    
    @available(*, unavailable)
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func draw(_ rect: CGRect) {
        let center = CGPoint(x: rect.midX, y: rect.midY)
        let radius = rect.width / 2 - lineWidth / 2
        
        let sorted = segments.sorted(by: { $0.key < $1.key })
        assert(sorted.count == total)
        for (index, color) in sorted {
            let (start, end) = startAndEndRadiansFor(index: index)
            color.setStroke()
            let path = UIBezierPath(arcCenter: center, radius: radius, startAngle: start, endAngle: end, clockwise: true)
            path.lineWidth = lineWidth
            path.stroke()
        }
    }
    
    public func updateSegments(with dict: [Int: UIColor]) {
        segments = dict
        setNeedsDisplay()
    }
    
    // MARK: - Private
    
    private func startAndEndRadiansFor(index: Int) -> (CGFloat, CGFloat) {
        assert(index < total)
        let step = CGFloat(360 / total)
        let start = CGFloat(index) * step
        let end = start + step
        let startRadian = CGFloat(start - 90) * CGFloat.pi / 180.0
        let endRadian = CGFloat(end - 90) * CGFloat.pi / 180.0
        return (startRadian, endRadian)
    }
}