import UIKit
import MobileCoreServices

enum CatError: Error {
   case invalidTypeIdentifier
}

protocol Shareable where Self: NSObject {
    static var shareIdentifier: String { get }
}

extension Shareable {
    static var shareIdentifier: String {
        let bundle = Bundle.main.bundleIdentifier!
        let typeString = String(describing: type(of: self))
        return "\(bundle).\(typeString)"
    }
}

final class Cat: NSObject, Shareable {

   let name: String
   let image: UIImage

   init(name: String, image: UIImage) {
       self.name = name
       self.image = image
       super.init()
   }

   var data: Data? {
       return """
           {
               "name": "\(name)",
               "image": "\(UIImageJPEGRepresentation(image, 1.0)!.base64EncodedString())"
           }
           """.data(using: .utf8)
   }

   init(data: Data) {
       let json = try! JSONSerialization.jsonObject(with: data, options: []) as! [String: Any]
       name = json["name"] as! String
       let imageData = Data(base64Encoded: json["image"] as! String)!
       image = UIImage(data: imageData)!
       super.init()
   }
}

// Providing Cat to destinationApp
extension Cat: NSItemProviderWriting {

   // Tell which identifiers are cat will be conforming to
   static var writableTypeIdentifiersForItemProvider: [String] {
       // General identifiers are not recommended, specific identifiers are welcome
       return [Cat.shareIdentifier, kUTTypeImage as String, kUTTypePlainText as String]
   }

   // Prepare data for providing to destinationAPP
   func loadData(withTypeIdentifier typeIdentifier: String, forItemProviderCompletionHandler completionHandler: @escaping (Data?, Error?) -> Void) -> Progress? {

       switch typeIdentifier {
       case Cat.shareIdentifier:
           completionHandler(data, nil)
       case kUTTypeImage as NSString as String:
           completionHandler(UIImageJPEGRepresentation(image, 1.0), nil)
       case kUTTypePlainText as NSString as String:
           completionHandler(name.data(using: .utf8), nil)
       default:
           completionHandler(nil, CatError.invalidTypeIdentifier)
       }

       // I'm not returning any progress
       return nil
   }
}

// Receiving cat from sourceApp
extension Cat: NSItemProviderReading {

   // Tell which indentifiers cal will be expecting
   static var readableTypeIdentifiersForItemProvider: [String] {
       return [Cat.shareIdentifier, kUTTypeImage as String, kUTTypePlainText as String]
   }

   static func object(withItemProviderData data: Data, typeIdentifier: String) throws -> Cat {

       switch typeIdentifier {
       case Cat.shareIdentifier:
           return Cat(data: data)
       case kUTTypeImage as NSString as String:
           return Cat(name: "no name", image: UIImage(data: data)!)
       case kUTTypePlainText as NSString as String:
           return Cat(name: String(data: data, encoding: .utf8)!, image: UIImage())
       default:
           throw CatError.invalidTypeIdentifier
       }
   }
}