Gemini/Gemini-iOS/HomepagePrefView.swift

//
//  HomepagePrefView.swift
//  Gemini-iOS
//
//  Created by Shadowfacts on 6/15/21.
//

import SwiftUI

struct HomepagePrefView: View {
    @State private var url: URL? = Preferences.shared.homepage
    @State private var focus = false
    
    var body: some View {
        List {
            // use a custom binding to allow the state variable to be nil temporarily, and update the pref when not
            HomepagePrefTextField(value: Binding(get: {
                url
            }, set: { (newVal) in
                self.url = newVal
                if let newVal = newVal {
                    Preferences.shared.homepage = newVal
                }
            }), focus: $focus)
        }
        .navigationBarTitle("Homepage")
        .onAppear {
            focus = true
        }
        .onDisappear {
            // if the text field was empty when we disappeared, reset to the default homepage
            if url == nil {
                Preferences.shared.homepage = AppDelegate.defaultHomepage
            }
        }    }
}

struct HomepagePrefTextField: UIViewRepresentable {
    @Binding private var value: URL?
    @Binding private var focus: Bool
    
    init(value: Binding<URL?>, focus: Binding<Bool>) {
        self._value = value
        self._focus = focus
    }
    
    func makeUIView(context: Context) -> UITextField {
        let field = UITextField()
        field.addTarget(context.coordinator, action: #selector(Coordinator.textChanged), for: .editingChanged)
        field.clearButtonMode = .whileEditing
        field.placeholder = AppDelegate.defaultHomepage.absoluteString
        // fix for text field expanding horizontally when text grows
        field.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        return field
    }
    
    func updateUIView(_ uiView: UITextField, context: Context) {
        uiView.text = value?.absoluteString
        context.coordinator.binding = $value
        if focus {
            DispatchQueue.main.async {
                uiView.becomeFirstResponder()
                focus = false
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        return Coordinator(binding: $value)
    }
    
    class Coordinator: NSObject {
        var binding: Binding<URL?>
        
        init(binding: Binding<URL?>) {
            self.binding = binding
        }
        
        @objc func textChanged(_ textField: UITextField) {
            if let text = textField.text,
               !text.isEmpty {
                if let url = URL(string: text) {
                    binding.wrappedValue = url
                }
            } else {
                binding.wrappedValue = nil
            }
        }
    }
}

struct HomepagePrefView_Previews: PreviewProvider {
    static var previews: some View {
        HomepagePrefView()
    }
}