ColorGenerator.swift

//
//  ColorGenerator.swift
//  Color Generator
//
//  Created by mbcharbonneau on 1/6/15.
//  Copyright (c) 2015 Once Living LLC. All rights reserved.
//

import Foundation
import UIKit

class ColorGenerator {

    fileprivate let goldenRatioConjugate: Float = (sqrt(5.0) - 1.0) / 2.0
    fileprivate let gradientDistance: Float = 0.3
    fileprivate var randomHue: Float

    var saturation: Float
    var brightness: Float

    init(saturation: Float = 0.5, brightness: Float = 0.95) {
        srand48(time(nil))
        self.randomHue = Float(drand48())
        self.saturation = saturation
        self.brightness = brightness
    }

    // Returns a new random color. Each call will yeild a color that is visually
    // distinct from the previous random color.

    func random() -> UIColor {
        randomHue += goldenRatioConjugate
        randomHue.formTruncatingRemainder(dividingBy: 1.0)

        return UIColor(hue: CGFloat(randomHue), saturation: CGFloat(saturation), brightness: CGFloat(brightness), alpha: 1.0)
    }

    // Returns a pair of random colors suitable for a nice gradient.

    func gradientColors() -> (start: UIColor, end: UIColor) {
        let startHue: Float = Float(drand48()).truncatingRemainder(dividingBy: 1.0)
        let endHue: Float = (startHue + gradientDistance).truncatingRemainder(dividingBy: 1.0)

        let start = UIColor(hue: CGFloat(startHue), saturation: CGFloat(saturation), brightness: CGFloat(brightness), alpha: 1.0)
        let end = UIColor(hue: CGFloat(endHue), saturation: CGFloat(saturation), brightness: CGFloat(brightness), alpha: 1.0)

        return (start, end)
    }

    // Create a random variant of the given baseColor, using distance to
    // determine how much to change the RGB values.

    func variation(of baseColor: UIColor, distance: CGFloat) -> UIColor {
        var red: CGFloat = 0.0
        var green: CGFloat = 0.0
        var blue: CGFloat = 0.0

        baseColor.getRed( &red, green: &green, blue: &blue, alpha: nil )

        let randomRed: CGFloat = CGFloat(drand48()).truncatingRemainder(dividingBy: distance)
        let randomGreen: CGFloat = CGFloat(drand48()).truncatingRemainder(dividingBy: distance)
        let randomBlue: CGFloat = CGFloat(drand48()).truncatingRemainder(dividingBy: distance)

        red += (red + randomRed > 1.0) ? randomRed * -1.0 : randomRed
        green += (red + randomGreen > 1.0) ? randomGreen * -1.0 : randomGreen
        blue += (red + randomBlue > 1.0) ? randomBlue * -1.0 : randomBlue

        return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
    }

}