import SwiftUI
import UIKit

struct TextInputView: View {
    @State private var textFieldText = ""
    
    var body: some View {
        TextField("Type here", text: $textFieldText)
            .textFieldStyle(RoundedBorderTextFieldStyle())
            .padding()
    }
}

struct KeyboardAnchoredContainer<Content: View>: UIViewControllerRepresentable {
    
    typealias ViewController = KeyboardAnchoredContainerViewController
    
    @ViewBuilder var content: () -> Content
    
    func makeUIViewController(context: Context) -> ViewController<Content> {
        ViewController(content: content())
    }
    func updateUIViewController(_ uiViewController: ViewController<Content>, context: Context) {}
}

class KeyboardAnchoredContainerViewController<Content: View>: UIViewController {
    
    var content: Content
    
    init(content: Content) {
        self.content = content
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        setUpContent()
        setUpInput()
    }
    
    private func setUpContent() {
        let hostingView = UIHostingController(rootView: content)
        hostingView.view.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(hostingView.view)
        
        // Anchor content to top of keyboard layout
        NSLayoutConstraint.activate([
            hostingView.view.bottomAnchor.constraint(equalTo: view.keyboardLayoutGuide.topAnchor),
            hostingView.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            hostingView.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            hostingView.view.topAnchor.constraint(equalTo: view.topAnchor),
        ])
    }
    
    private func setUpInput() {
        let textInputView = TextInputView()
        let hostingView = UIHostingController(rootView: textInputView)
        view.addSubview(hostingView.view)
        hostingView.view.translatesAutoresizingMaskIntoConstraints = false
        
        // Anchor input to top of keyboard layout
        NSLayoutConstraint.activate([
            hostingView.view.bottomAnchor.constraint(equalTo: view.keyboardLayoutGuide.topAnchor),
            hostingView.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            hostingView.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            hostingView.view.heightAnchor.constraint(equalToConstant: 46)
        ])
    }
}

struct ContentView: View {
    
    var body: some View {
        KeyboardAnchoredContainer {
            VStack {
                ScrollView {
                    ForEach(0..<20) { index in
                        HStack {
                            Text("Item \(index + 1)")
                                .padding()
                            Spacer()
                        }
                    }
                }
                .scrollDismissesKeyboard(.interactively)
                .scrollClipDisabled()
                .defaultScrollAnchor(.bottom)
                // Inset content slightly to avoid overlap with text input.
                .contentMargins([.bottom], EdgeInsets(top: 0, leading: 0, bottom: 40, trailing: 0))
            }
        }
        // This is key, otherwise the text input taps into SwiftUI's keyboard safe area avoidance.
        .ignoresSafeArea()
    }
}

#Preview {
    ContentView()
}