using System.Text;

using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Presenters;
using Avalonia.Interactivity;

namespace GSS2.Views;

public partial class NumericKeyboardView : UserControl
{
    public static readonly StyledProperty<double?> ValueProperty = AvaloniaProperty.Register<NumericKeyboardView, double?>(nameof(Value));
    public double? Value
    {
        get => GetValue(ValueProperty);
        set => SetValue(ValueProperty, value);
    }
    public static readonly RoutedEvent<RoutedEventArgs> ClosedEvent = RoutedEvent.Register<NumericKeyboardView, RoutedEventArgs>(nameof(KeyboardClosed), RoutingStrategies.Bubble);
    public event EventHandler<RoutedEventArgs> KeyboardClosed
    {
        add => AddHandler(ClosedEvent, value);
        remove => RemoveHandler(ClosedEvent, value);
    }

    private readonly TextPresenter? _presenter;

    private StringBuilder _text = new();
    private bool changingValue = false;
    private int _cursor = 0;

    public NumericKeyboardView()
    {
        InitializeComponent();

        ValueProperty.Changed.AddClassHandler<NumericKeyboardView>((sender, value) =>
        {
            if (sender != this)
                return;
            if (changingValue)
                return;
            if (value.NewValue is not double doubleValue)
            {
                changingValue = true;
                _text = new();
                _cursor = _text.Length;
                changingValue = false;
                UpdateDisplay();
                return;
            }
            changingValue = true;
            _text.Clear();
            _text.Insert(0, doubleValue.ToString("G6").Replace(".", ","));
            _cursor = _text.Length;
            changingValue = false;
            UpdateDisplay();
        });

        _presenter = this.FindControl<TextPresenter>("Text");

        if (Value is not null)
            _text.Insert(0, Value.Value.ToString("G6").Replace(".", ","));
        _cursor = _text.Length;

        _presenter?.ShowCaret();
        UpdateDisplay();
    }

    private void KeyPressed(object? sender, RoutedEventArgs e)
    {
        if (sender is not Button btn || btn.Content is not string symbol) return;

        if (symbol == "," && _cursor == 0)
            return;
        if (symbol == "," && _text.ToString().Contains(','))
        {
            var index = _text.ToString().IndexOf(",");
            _text.Remove(index, 1);
            if (index < _cursor)
                _cursor--;
        }

        _text.Insert(_cursor, symbol);
        _cursor++;
        UpdateDisplay();
    }

    private void Backspace(object? sender, RoutedEventArgs e)
    {
        if (_cursor > 0)
        {
            _cursor--;
            _text.Remove(_cursor, 1);
            UpdateDisplay();
        }
    }

    private void MoveCursorLeft(object? sender, RoutedEventArgs e)
    {
        _cursor = Math.Max(0, _cursor - 1);
        UpdateDisplay();
    }

    private void MoveCursorRight(object? sender, RoutedEventArgs e)
    {
        _cursor = Math.Min(_text.Length, _cursor + 1);
        UpdateDisplay();
    }

    private void Accept(object? sender, RoutedEventArgs e)
    {
        if (double.TryParse(_text.ToString().Replace(",", "."), out double value))
            Value = value;
    }

    private void Cancel(object? sender, RoutedEventArgs e) => Value = null;

    private void UpdateDisplay()
    {
        if (_presenter is null) return;

        _presenter.Text = _text.ToString();
        _presenter.CaretIndex = _cursor;
        _presenter.InvalidateVisual();

        if (double.TryParse(_text.ToString().Replace(",", "."), out double value))
            Value = value;
    }
}