/// Interface that fetches image from a source.
/// Image can be fetched from a web service or even from a local source.
internal protocol ImageFetcher {
    func fetch(then completion: @escaping (UIImage?, Error?) -> Void)
}

/// User Model
public class User {
    // Stores the
    public var name: String

    /// Private image holder for the user.
    /// Nil either when image is not there or not fetched.
    var iProfileImage: UIImage?

    /// Display profile image for the user.
    /// Returns either the actual user profile image or the default display image.
    public var profileImage: UIImage {
        return iProfileImage ?? .defaultProfileImage
    }

    init(name:String) {
        self.name = name
    }

    func fetchProfileImage(fetcher: ImageFetcher, then completion: @escaping (Bool)-> Void) {
        fetcher.fetch { (image, error) in
            if let fetchError = error {
                print("Failed to fetch Image with error - \(fetchError)")
                completion(false)
            } else if let fetchedImage = image {
                print("Image fetched")
                self.iProfileImage = fetchedImage
                completion(true)
            } else {
                print("Failed to fetch Image with unknown error")
                completion(false)
            }
        }
    }
}