@objc(OtpAutoFillViewManager)
class OtpAutoFillViewManager: RCTViewManager {

    override func view() -> (OtpAutoFillView) {
        return OtpAutoFillView()
    }
}

class OtpAutoFillView : UIView, UITextFieldDelegate {
    
    var textField: UITextField!

    @objc var color: String = "#000000" {
        didSet {
            textField.textColor = hexStringToUIColor(hexColor: color)
        }
    }

    @objc var space: NSNumber = 28.0 {
        didSet {
            textField.defaultTextAttributes.updateValue(space, forKey: NSAttributedString.Key.kern)
        }
    }

    @objc var fontSize: NSNumber = 24.0 {
        didSet {
            textField.font = UIFont.systemFont(ofSize: CGFloat(fontSize), weight: .heavy)
        }
    }

    @objc var length: NSNumber = 6 {
        didSet {
            textField.text = ""
        }
    }

    @objc var onComplete: RCTDirectEventBlock?

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupView()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupView()
    }
    
    func setupView() {
        // Text field configs
        textField = UITextField()
        textField.delegate = self
        textField.translatesAutoresizingMaskIntoConstraints = false
        textField.textColor = hexStringToUIColor(hexColor: color)
        textField.defaultTextAttributes.updateValue(space, forKey: NSAttributedString.Key.kern)
        textField.font = UIFont.systemFont(ofSize: CGFloat(fontSize), weight: .heavy)
        textField.textContentType = .oneTimeCode
        textField.keyboardType = .numberPad
        textField.textAlignment = .center

        // Add text field to UIView
        self.addSubview(textField)

        // Make text field to take whole UIView size
        NSLayoutConstraint.activate([
            textField.topAnchor.constraint(equalTo: self.topAnchor),
            textField.leftAnchor.constraint(equalTo: self.leftAnchor),
            textField.rightAnchor.constraint(equalTo: self.rightAnchor),
            textField.bottomAnchor.constraint(equalTo: self.bottomAnchor)
        ])

        // Open keyboard
        textField.becomeFirstResponder()
    }

    // Text length limit logics
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        let currentString: NSString = (textField.text ?? "") as NSString
        let newString: NSString =
            currentString.replacingCharacters(in: range, with: string) as NSString
        
        // Call the onComplete event when OTP has been entered
        if (newString.length == length.intValue) {
            if onComplete != nil {
                onComplete!(["code": newString])
            }
        }
        
        return newString.length <= length.intValue
    }

    // Color converter helper
    func hexStringToUIColor(hexColor: String) -> UIColor {
        let stringScanner = Scanner(string: hexColor)

        if(hexColor.hasPrefix("#")) {
            stringScanner.scanLocation = 1
        }
        var color: UInt32 = 0
        stringScanner.scanHexInt32(&color)

        let r = CGFloat(Int(color >> 16) & 0x000000FF)
        let g = CGFloat(Int(color >> 8) & 0x000000FF)
        let b = CGFloat(Int(color) & 0x000000FF)

        return UIColor(red: r / 255.0, green: g / 255.0, blue: b / 255.0, alpha: 1)
    }
}