protocol ThatHidable {
    var isHidden: Bool { get set }
}

protocol ThatShapeLayer: ThatHidable {
    var fillColor: CGColor? { get set }
    var strokeColor: CGColor? { get set }
}

protocol ThatConfigurableBattery {
    var border: ThatShapeLayer { get }
    var happyFace: ThatShapeLayer { get }
    var sadFace: ThatShapeLayer { get }
    var chargeBar: ThatShapeLayer { get }
}

extension CAShapeLayer: ThatShapeLayer {}

class ThatBattery: UIView, ThatConfigurableBattery {
    private let borderLayer = CAShapeLayer()
    private let happyFaceLayer = CAShapeLayer()
    private let sadFaceLayer = CAShapeLayer()
    private let chargeBarLayer = CAShapeLayer()

    var border: ThatShapeLayer {
        return borderLayer
    }

    var happyFace: ThatShapeLayer {
        return happyFaceLayer
    }

    var sadFace: ThatShapeLayer {
        return sadFaceLayer
    }

    var chargeBar: ThatShapeLayer {
        return chargeBarLayer
    }
}