Satellites.swift

import UIKit
import XCPlayground

extension UIView {
    
    var diagonal : CGFloat {
        return sqrt(pow(self.frame.width, 2) + pow(self.frame.height, 2))
    }
    
    var radius : CGFloat {
        return diagonal / 2
    }
}

extension CGPoint {
    
    func getPoint(atDistance distance: CGFloat, overAngleRadians angle:CGFloat) -> CGPoint {
        
        let x = self.x
        let y = self.y
        
        let dx = (distance * cos(angle))
        let dy = (distance * sin(angle))
        
        return CGPoint(x: (dx + x), y: (dy + y))
    }
}

protocol Planet {
    
    var center : CGPoint { get }
    var superview : UIView? { get }
    var radius : CGFloat { get }
    
    func convertPoint(point: CGPoint, toView: UIView?) -> CGPoint
}

extension Planet {
    
    private func encirclePoint(point : CGPoint, distance:CGFloat, inParts parts: Int) -> [CGPoint] {
        
        let angle = 2 * CGFloat(M_PI) / CGFloat(parts) // critical part, you need radians for trigonometry
        var runningAngle : CGFloat = (CGFloat(M_PI) / 2) * (-1) // start at the top, change the multiplier to adjust, -1 is top
        
        var points : [CGPoint] = []
        
        for _ in 0..<parts {
            let circlePoint = point.getPoint(atDistance: distance, overAngleRadians: runningAngle)
            points.append(circlePoint)
            runningAngle += angle
        }
        
        return points
    }
    
    func encircle(withViews satellites : [UIView], withMargin margin : CGFloat) {
        
        guard !(satellites.isEmpty) else { // if there are no subviews : abort
            return
        }
        
        let distance = radius + margin
        var supercenter = CGPointZero
        
        if let satelliteSuperview = satellites.first?.superview, let superview = superview where satelliteSuperview != superview { // this expects all satellites to have the same superview
            supercenter = convertPoint(center, toView: satelliteSuperview)
        } else {
            supercenter = center
        }
        
        let points = encirclePoint(supercenter, distance: distance, inParts: satellites.count)
        
        guard satellites.count == points.count else { // if the count is not the same : abort
            return
        }
        
        for (point, satellite) in zip(points,satellites) { satellite.center = point }
    }
}


// tests

class PlanetView : UIView, Planet { }

let view : UIView = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 400))
view.backgroundColor = UIColor.blackColor()

let planet = PlanetView(frame: CGRect(x: 115, y: 100, width: 200, height: 200))
planet.backgroundColor = UIColor(red: 0.0, green: 0.3, blue: 1.0, alpha: 1.0)
planet.layer.cornerRadius = planet.frame.height / 2
view.addSubview(planet)

let satFrame = CGRect(x: 0, y: 0, width: 25, height: 25)

let satOne = UIView(frame: satFrame)
let satTwo = UIView(frame: satFrame)
let satThree = UIView(frame: satFrame)
let satFour = UIView(frame: satFrame)
let satFive = UIView(frame: satFrame)
let satSix = UIView(frame: satFrame)

satOne.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
satTwo.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.6)
satThree.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.6)
satFour.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.6)
satFive.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.6)
satSix.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.6)

satOne.layer.cornerRadius = satFrame.height / 2
satTwo.layer.cornerRadius = satFrame.height / 2
satThree.layer.cornerRadius = satFrame.height / 2
satFour.layer.cornerRadius = satFrame.height / 2
satFive.layer.cornerRadius = satFrame.height / 2
satSix.layer.cornerRadius = satFrame.height / 2

view.addSubview(satOne)
view.addSubview(satTwo)
view.addSubview(satThree)
view.addSubview(satFour)
view.addSubview(satFive)
//view.addSubview(satSix)

planet.encircle(withViews: [satOne,satTwo,satThree,satFour,satFive], withMargin: 25)

XCPlaygroundPage.currentPage.liveView = view