CustomTabbar.swift

//
//  HomeTabbar.swift
//  Alamofire
//
//  Created by DoanDuyPhuong on 6/29/20.
//

import Foundation
import UIKit

@IBDesignable
class HomeTabBar: UITabBar {

    let curveTop: CGFloat = 40
    var curveRadius: CGFloat {
        let height = self.frame.height - self.getSafeBottom()
        return (height / 2) + curveTop
//        return 42
    }

    var shapLayer: CAShapeLayer?
    var circleLayer: CAShapeLayer?
    
    var circleYellowRadius: CGFloat {
//        return self.curveRadius
        let height = self.frame.height - self.getSafeBottom()
//        return (height / 2) + curveTop
        return 70
    }
        
    override func draw(_ rect: CGRect) {
        self.addShape()
        self.addYellowCicle()
    }
    
    private func addShape() {
        let shape = CAShapeLayer()
        shape.path = self.createPath()
        shape.strokeColor = UIColor.red.cgColor
        shape.fillColor = UIColor.yellow.cgColor
        shape.lineWidth = 1.0
        
        if let s = self.shapLayer {
            self.layer.replaceSublayer(s, with: shape)
        }
        else {
            self.layer.insertSublayer(shape, at: 0)
        }
        
        self.shapLayer = shape
    }
    
    private func createPath() -> CGPath {
        // https://stackoverflow.com/questions/22212440/using-math-class-to-convert-cosine-into-degrees?fbclid=IwAR0U6sSRByN_sV0EeQt0Q5I3HLOekxPiqe-iKv6eNjRBpuYjc8U68_IWZDg
        
        // cos(x) = angle
        // -> x =
        let angle = (self.curveRadius - self.curveTop) / self.curveRadius
        
        let angleRadian = acos(angle)
        let engleToDegree = angleRadian * 180 / .pi
        let startAngleDree = 180 + 90 - engleToDegree
        let endAngleDree = 180 + 90 + engleToDegree
        
        // cạnh đáy của tam giác cân ~ pitago
        let bc = pow(self.curveRadius, 2)
        let hc = bc - pow(self.curveRadius - self.curveTop, 2)
        let ac = sqrt(hc)
        
        let path = UIBezierPath()
        let centerWidth = self.frame.width / 2
        path.move(to: .zero)
        path.addLine(to: .init(x: centerWidth - ac, y: 0))
        
        path.move(to: .init(x: centerWidth - ac, y: 0))
        path.addArc(withCenter: self.getCenter(), radius: self.curveRadius, startAngle: .pi * startAngleDree / 180.0, endAngle: .pi * endAngleDree / 180, clockwise: true)
        
        path.move(to: .init(x: centerWidth + ac, y: 0))
        path.addLine(to: CGPoint.init(x: self.frame.width, y: 0))
        
        path.close()
        return path.cgPath
    }
    
    private func getCenter() -> CGPoint {
        return CGPoint.init(x: self.frame.width / 2, y: (self.frame.height - self.getSafeBottom() ) / 2  )
    }
    
    private func getCenterCicle() -> CGPoint {
        return CGPoint.init(x: self.frame.width / 2, y: (self.frame.height / 4 - self.getSafeBottom() ) / 2 )
    }
    
    //
    private func addYellowCicle() {

        
        let radius = self.circleYellowRadius
        let shape = CAShapeLayer()
        shape.fillColor = UIColor.red.cgColor
        shape.path = UIBezierPath.init(arcCenter: self.getCenterCicle(), radius: radius / 2, startAngle: 0, endAngle: .pi * 2, clockwise: true).cgPath
        
        if let s = self.circleLayer {
            self.layer.replaceSublayer(s, with: shape)
        } else {
            self.layer.insertSublayer(shape, at: 1)
        }
        self.circleLayer = shape
    }
    
    private func getSafeBottom() -> CGFloat {
        if #available(iOS 11.0, *) {
            return self.safeAreaInsets.bottom
        } else {
            return 0
        }
    }
}

extension HomeTabBar {
    
    override var traitCollection: UITraitCollection {
        return UITraitCollection.init(horizontalSizeClass: .unspecified)
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        self.itemPositioning = .centered
    }
}