KeyboardAware.swift

import Typist

protocol KeyboardAware {
    var keyboard: Typist { get }
    var contentInset: UIEdgeInsets { get }
    var scrollIndicatorInsets: UIEdgeInsets { get }
}

extension KeyboardAware where Self: UIScrollView {
    func observeKeyboard() {
        keyboard.on(event: .willShow) { [unowned self] options in
            self.contentInset.bottom = options.startFrame.height
            self.scrollIndicatorInsets = self.contentInset
        }.on(event: .willHide) { [unowned self] options in
            UIView.animate(withDuration: options.animationDuration) {
                self.contentInset.bottom = 0
                self.scrollIndicatorInsets = self.contentInset
            }
        }.start()
    }
}

class ScrollView: UIScrollView, KeyboardAware {
    let keyboard = Typist.shared
    
    override func willMove(toSuperview newSuperview: UIView?) {
        super.willMove(toSuperview: newSuperview)
        observeKeyboard()
    }
}