import ImageIO
import MobileCoreServices

class MyAnimatedViewTToBeRecordedAsGif: UIView {

    private var timer: Timer!
    private var isRecording = false
    private var images = [UIImage]()
    private var timeInterval: TimeInterval = 0.05 // 20 frames per sec

    func startRecordingGif() {
        guard !isRecording else { return }

        timer = Timer(timeInterval: timeInterval, target: self, selector: #selector(recordFrame), userInfo: nil, repeats: true)
        RunLoop.current.add(timer, forMode: .defaultRunLoopMode)
        isRecording = true

        setupRecordingGif()

        timer.fire()
    }

    private func stopRecordingGif() {
        guard isRecording else { return }

        isRecording = false
        timer.invalidate()

        finalizeRecordigGif()
    }

    @objc func recordFrame() {
        guard images.count <= Int(21 / timeInterval) else { // 21 sec - duration of the animation
            stopRecordingGif()
            return
        }

        images.append(capture())
    }

    // capturing 'self'
    private func capture() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
        defer { UIGraphicsEndImageContext() }
        drawHierarchy(in: bounds, afterScreenUpdates: true)
        return UIGraphicsGetImageFromCurrentImageContext() ?? UIImage()
    }

    private func setupRecordingGif() {
        images = []
    }

    private func finalizeRecordigGif() {
        let fileProperties: CFDictionary = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: 0]]  as CFDictionary
        let frameProperties: CFDictionary = [kCGImagePropertyGIFDictionary as String: [(kCGImagePropertyGIFDelayTime as String): timeInterval]] as CFDictionary

        let documentsDirectoryURL: URL? = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
        let fileURL: URL? = documentsDirectoryURL?.appendingPathComponent("animated.gif")

        if let url = fileURL as CFURL? {
            if let destination = CGImageDestinationCreateWithURL(url, kUTTypeGIF, images.count, nil) {
                CGImageDestinationSetProperties(destination, fileProperties)
                for image in images {
                    if let cgImage = image.cgImage {
                        CGImageDestinationAddImage(destination, cgImage, frameProperties)
                    }
                }
                if !CGImageDestinationFinalize(destination) {
                    print("Failed to finalize the image destination")
                }
                print("Url = \(fileURL)")
            }
        }
    }
}