Attenuates a UIColor, returning a dynamic color

UIColor+Attenuated.swift

import UIKit

extension UIColor {

    /// Creates a dynamic color from the receiver with attenuated brightness.
    ///
    /// This method works correctly with light and dark mode. A dynamic color is
    /// returned, so if the user switches to dark mode, the attenuated dark mode version of `self`
    /// will be displayed.
    func attenuated(by attenuation: CGFloat) -> UIColor {
        func attenuate(_ baseColor: UIColor, by attenuation: CGFloat) -> UIColor {
            var hue: CGFloat = 0
            var saturation: CGFloat = 0
            var brightness: CGFloat = 0
            var alpha: CGFloat = 0

            baseColor.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha)
            
            brightness *= attenuation
            
            return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: alpha)
        }
        
        return UIColor(dynamicProvider: { traitCollection in
            var result: UIColor = .white
            traitCollection.performAsCurrent {
                result = attenuate(self, by: attenuation)
            }
            return result
        })

    }

}