Advance json parsing pt1

/**
 * A simple struct that holds UIColor and UIFont
 */
struct Theme:Decodable{
    enum CodingKeys: String, CodingKey {/*CodingKeys are required when you want to customize your json (Be able to rename properties) parsing*/
        case color
        case font
    }
    let color: UIColor
    let font: UIFont
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        color = try container.decode(key: .color, transformer: ColorTransformer())
        font = try container.decode(key: .font, transformer: UIFontTransformer())
    }
}

/**
 * The transformer that handles parsing the string value to UIColor
 * TODO: ⚠️️ Add support for 0x00FF00FF (Aka hex with alpha value)
 * ## EXAMPLE: "color":"white"
 */
class ColorTransformer: DecodingContainerTransformer {
    enum Error: Swift.Error {
        case cannotCreateColor(hex: String)
    }
    
    func decode(input: String) throws -> UIColor {
        guard let color = try? ColorUtils.color(input) else {
            throw Error.cannotCreateColor(hex: input)
        }
        return color
    }
}
/**
 * The transformer that handles parsing the dictionary (Aka fontName and fontSize) value to UIColor
 * ## EXAMPLE: "font":{"name":".SFUIText","size":"16"}
 */
class UIFontTransformer: DecodingContainerTransformer {
    enum Error: Swift.Error {
        case cannotCreateFont(name: [String: String])
    }
    
    func decode(input: [String: String]) throws -> UIFont {
        guard let name = input["name"],
              let fontSize = input["size"],
              let fontSizeAsDouble = Double(fontSize),
              let font = UIFont(name: name, size: CGFloat(fontSizeAsDouble))
        else {
            throw Error.cannotCreateFont(name: input)
        }
        return font
    }
}

/**
 * Makes the code more reusable/modular
 */
public protocol DecodingContainerTransformer {
    associatedtype DecodingInput
    associatedtype DecodingOutput
    func decode(input: DecodingInput) throws -> DecodingOutput
}
/**
 * Makes the code more reusable/modular
 */
extension KeyedDecodingContainer {
    public func decode<Transformer: DecodingContainerTransformer>(key: Key, transformer: Transformer) throws -> Transformer.DecodingOutput where Transformer.DecodingInput: Decodable {
        return try transformer.decode(input: try decode(Transformer.DecodingInput.self, forKey: key))
    }
    public func decodeIfPresent<Transformer: DecodingContainerTransformer>(key: Key, transformer: Transformer) throws -> Transformer.DecodingOutput? where Transformer.DecodingInput: Decodable {
        return try decodeIfPresent(Transformer.DecodingInput.self, forKey: key).map(transformer.decode)
    }
}

let urlStr: String = Bundle.main.resourcePath! + "/theme.json"
guard let data: Data = FileParser.data(urlStr) else {
    fatalError("Wrong file path")
}
guard let theme: Theme = try? decode(data: data) else {
    fatalError("Can't convert JSON to Theme")
}
Swift.print("Theme color: \(theme.color)") // UIExtendedSRGBColorSpace 1 1 1 1
Swift.print("Theme font: \(theme.font)") // <UICTFont: 0x7faef7c02850> font-family: ".SFUIText"; font-weight: normal; font-style: normal; font-size: 16.00pt