//
//  ContentView.swift
//  textinput
//
//  Created by Venin Alexander on 3/22/22.
//

import SwiftUI

extension View {
    func hideKeyboard() {
        UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
    }
}

struct InputViewRepresentable: UIViewRepresentable {

    @Binding var text: String
    @Binding var isEditing: Bool

    var keyboardType: UIKeyboardType = .asciiCapable
    var font: UIFont?

    func makeUIView(context: Context) -> UITextView {
        let textView = UITextView()
        textView.isSelectable = true
        textView.isUserInteractionEnabled = true
        textView.isEditable = true
        textView.delegate = context.coordinator
        textView.isScrollEnabled = false
        textView.backgroundColor = .clear
        textView.textContainerInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
        textView.textContainer.lineFragmentPadding = 0
        textView.autocorrectionType = .no
        textView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)

        if let font = self.font {
            textView.font = font
        }
        return textView
    }

    func updateUIView(_ uiView: UITextView, context: Context) {
        uiView.text = text
        if let font = self.font {
            uiView.font = font
        }
        if uiView.text != self.text {
            uiView.text = self.text
        }
        if uiView.window != nil, isEditing {
            uiView.becomeFirstResponder()
        }
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, UITextViewDelegate {
        private let parent: InputViewRepresentable

        init(_ parent: InputViewRepresentable ) {
            self.parent = parent
        }

        func textViewDidChange(_ textView: UITextView) {
            DispatchQueue.main.async { [weak self] in
                self?.parent.text = textView.text
            }
        }

        func textViewDidBeginEditing(_ textView: UITextView) {
            DispatchQueue.main.async { [weak self] in
                self?.parent.isEditing = true
            }
        }

        func textViewDidEndEditing(_ textView: UITextView) {
            DispatchQueue.main.async { [weak self] in
                self?.parent.isEditing = false
            }
        }
    }
}

struct ContentView: View {
    @State var text: String = ""
    @State var isEditing: Bool = false
    @State var isValid = true
    
    var body: some View {
        VStack(spacing: 0) {
            Spacer()
            ScrollView(.vertical) {
                VStack(spacing: 40) {
                    Spacer()
                    
                    validationErrorMessage
                    
                    InputViewRepresentable(text: $text,
                                           isEditing: $isEditing,
                                           keyboardType: .asciiCapable,
                                           font: UIFont.systemFont(ofSize: 20))
                        .border(Color.black)
                        .padding(.top, 50)
                    
                    
                }
                .animation(.default, value: isValid)
                .animation(.default, value: isEditing)
                .padding(.horizontal, 20)
            }.frame(maxWidth: .infinity)
            Button("Validate") {
                hideKeyboard()
                isValid = false
            }
        }
    }
    
    @ViewBuilder
    private var validationErrorMessage: some View {
        if !isValid && !isEditing {
            Text("invalid input")
                .foregroundColor(Color.red)
                .transition(.opacity.combined(with: .move(edge: .top)))
        }
    }
}