UITextInput+AvoidCovered.swift

extension UITextInput where Self: UIView {
    
    func avoidCoveredByKeyboard(
        from view: UIView,
        _ offset: CGFloat = 0
    ) {
        NotificationCenter.default.addObserver(
            forName: UIApplication.keyboardWillShowNotification,
            object: nil,
            queue: .main
        ) { [weak self] note in
            guard let self = self, self.isFirstResponder else { return }
            
            let keyboardHeight: CGFloat
            if let keyboardFrame = note.userInfo?[UIApplication.keyboardFrameEndUserInfoKey]
                as? CGRect {
                keyboardHeight = keyboardFrame.height
            } else {
                keyboardHeight = 0
            }
            
            UIView.beginAnimations("ResizeForShowKeyboard", context: nil)
            UIView.setAnimationCurve(self.keyboardAnimationCurve(from: note.userInfo))
            UIView.setAnimationDuration(self.keyboardAnimationDuration(from: note.userInfo))
            view.transform = CGAffineTransform(translationX: 0, y: -(keyboardHeight + offset))
            UIView.commitAnimations()
        }
        
        NotificationCenter.default.addObserver(
            forName: UIApplication.keyboardWillHideNotification,
            object: nil,
            queue: .main
        ) { [weak self] note in
            guard let self = self, self.isFirstResponder else { return }
            
            UIView.beginAnimations("ResizeForHideKeyboard", context: nil)
            UIView.setAnimationCurve(self.keyboardAnimationCurve(from: note.userInfo))
            UIView.setAnimationDuration(self.keyboardAnimationDuration(from: note.userInfo))
            view.transform = CGAffineTransform.identity
            UIView.commitAnimations()
        }
    }
    
    private func keyboardAnimationCurve(from userInfo: [AnyHashable: Any]?) -> UIView.AnimationCurve {
        guard let index = userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] as? Int else {
            return .linear
        }
        
        if index >= 0, index <= 3 {
            return .linear
        } else {
            return UIView.AnimationCurve.init(rawValue: index) ?? .linear
        }
    }
    
    private func keyboardAnimationDuration(from userInfo: [AnyHashable: Any]?) -> TimeInterval {
        return userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? TimeInterval ?? 0
    }
}