using Avalonia;
using Avalonia.Media;
using Avalonia.Input;
using Avalonia.Controls;
using Avalonia.Media.Imaging;

using Mat = OpenCvSharp.Mat;
using Cv2 = OpenCvSharp.Cv2;

using GSS2.Core.Extentions;

namespace GSS2.UI.Core;

public class OpenCvImage : Control
{
    private class OpenCvBitmap : Bitmap
    {
        public OpenCvBitmap(Mat mat)
        : base(
            format: Avalonia.Platform.PixelFormat.Rgba8888,
            alphaFormat: Avalonia.Platform.AlphaFormat.Unpremul,
            data: mat.Data,
            size: new PixelSize(mat.Width, mat.Height),
            dpi: new Vector(96, 96),
            stride: (mat.DataEnd - mat.DataStart).ToInt32() / mat.Rows
        )
        { }
    }

    private Point? _lastmousePosition = null;
    private Dictionary<int, Point>? _lastTouchPositions = null;
    private float _zoom = 1;
    private float _panX = 0;
    private float _panY = 0;
    private OpenCvBitmap? _bitmap = null;

    public static readonly StyledProperty<Color> BackgroundProperty = AvaloniaProperty.Register<OpenCvImage, Color>(nameof(Background), defaultValue: Colors.Transparent);
    public Color Background
    {
        get => GetValue(BackgroundProperty);
        set => SetValue(BackgroundProperty, value);
    }
    public static readonly StyledProperty<Stretch> StretchModeProperty = AvaloniaProperty.Register<OpenCvImage, Stretch>(nameof(StretchMode), defaultValue: Stretch.Uniform);
    public Stretch StretchMode
    {
        get => GetValue(StretchModeProperty);
        set => SetValue(StretchModeProperty, value);
    }
    public static readonly StyledProperty<TileMode> TileModeProperty = AvaloniaProperty.Register<OpenCvImage, TileMode>(nameof(TileMode), defaultValue: TileMode.None);
    public TileMode TileMode
    {
        get => GetValue(TileModeProperty);
        set => SetValue(TileModeProperty, value);
    }
    public static readonly StyledProperty<Mat?> ImageProperty = AvaloniaProperty.Register<OpenCvImage, Mat?>(nameof(Image), defaultValue: null);
    public Mat? Image
    {
        get => GetValue(ImageProperty);
        set => SetValue(ImageProperty, value);
    }

    public OpenCvImage()
    : base()
    {
        DoubleTapped += (_, _) =>
        {
            _zoom = 1f;
            _panX = 0f;
            _panY = 0f;
        };
    }

    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
    {
        if (change.Property == ImageProperty)
        {
            _bitmap?.Dispose();
            _bitmap = null;

            if (Image is null)
                return;

            if (Image.Type() != OpenCvSharp.MatType.CV_8UC3 &&
                Image.Type() != OpenCvSharp.MatType.CV_8UC4 &&
                Image.Type() != OpenCvSharp.MatType.CV_16UC3 &&
                Image.Type() != OpenCvSharp.MatType.CV_16UC4)
                return;

            var image = new Mat();
            Image.CopyTo(image);

            if (image.Type() == OpenCvSharp.MatType.CV_16UC3)
                image.ConvertTo(image, OpenCvSharp.MatType.CV_8UC3, 1 / 256.0);
            if (image.Type() == OpenCvSharp.MatType.CV_16UC4)
                image.ConvertTo(image, OpenCvSharp.MatType.CV_8UC4, 1 / 256.0);

            var channels = image.Split();
            var alphaChannel = image.Channels() == 4 ? channels[4] : new Mat(Image.Size(), OpenCvSharp.MatType.CV_8UC1, new OpenCvSharp.Scalar(255));
            Cv2.Merge([channels[2], channels[0], channels[1], alphaChannel], image);

            _bitmap = new OpenCvBitmap(image);

            InvalidateVisual();
        }
        base.OnPropertyChanged(change);
    }

    protected override void OnPointerWheelChanged(PointerWheelEventArgs ea)
    {
        if (ea.Pointer.Type == PointerType.Mouse)
        {
            var position = ea.GetPosition(this);

            // Рассчитываем позицию в координатах изображения (до масштабирования)
            var imageX = (position.X - Bounds.Width / 2 - _panX) / _zoom;
            var imageY = (position.Y - Bounds.Height / 2 - _panY) / _zoom;

            // Применяем масштаб
            float zoomFactor = ea.Delta.Y > 0 ? 1.1f : 1 / 1.1f;
            _zoom *= zoomFactor;
            _zoom = Math.Clamp(_zoom, 1f, 10f);
            _zoom = (float)Math.Round(_zoom, 2);

            if (_zoom != 1f)
            {
                // Пересчитываем смещение так, чтобы указатель остался на месте
                _panX = (float)(position.X - Bounds.Width / 2 - imageX * _zoom);
                _panY = (float)(position.Y - Bounds.Height / 2 - imageY * _zoom);
            }
            else
            {
                // Если зум == 1, то возвращаем изображение к исходному смещению
                _panX = 0f;
                _panY = 0f;
            }
        }
        base.OnPointerWheelChanged(ea);
        InvalidateVisual();
    }
    protected override void OnPointerPressed(PointerPressedEventArgs ea)
    {
        if (ea.Pointer.Type == PointerType.Mouse)
        {
            if (ea.Properties.IsLeftButtonPressed)
            {
                if (ea.ClickCount == 2) // По двойному клику возвращаем изображение к смещение и зум к стандартным значениям
                {
                    _zoom = 1f;
                    _panX = 0f;
                    _panY = 0f;
                }
                else
                    _lastmousePosition = ea.GetPosition(this);
            }
        }
        else if (ea.Pointer.Type == PointerType.Touch)
        {
            if (_lastTouchPositions is null)
                _lastTouchPositions = new Dictionary<int, Point>();

            if (!_lastTouchPositions.ContainsKey(ea.Pointer.Id) && _lastTouchPositions.Count() < 2)
                _lastTouchPositions.Add(ea.Pointer.Id, ea.GetPosition(this));
            else if (_lastTouchPositions.ContainsKey(ea.Pointer.Id))
                _lastTouchPositions[ea.Pointer.Id] = ea.GetPosition(this);
        }
        base.OnPointerPressed(ea);
        InvalidateVisual();
    }
    protected override void OnPointerReleased(PointerReleasedEventArgs ea)
    {
        if (ea.Pointer.Type == PointerType.Mouse)
        {
            if (!ea.Properties.IsLeftButtonPressed)
                _lastmousePosition = null;
        }
        else if (ea.Pointer.Type == PointerType.Touch)
        {
            if (_lastTouchPositions is not null && _lastTouchPositions.ContainsKey(ea.Pointer.Id))
                _lastTouchPositions.Remove(ea.Pointer.Id);
        }
        base.OnPointerReleased(ea);
        InvalidateVisual();
    }
    protected override void OnPointerMoved(PointerEventArgs ea)
    {
        if (ea.Pointer.Type == PointerType.Mouse)
        {
            if (_lastmousePosition is null || _zoom == 1) // Если кнопка не нажата или зум == 1, то ничего не делаем
            {
                base.OnPointerMoved(ea);
                return;
            }
            var position = ea.GetPosition(this);
            _panX -= (float)(_lastmousePosition.Value.X - position.X);
            _panY -= (float)(_lastmousePosition.Value.Y - position.Y);
            _lastmousePosition = position;
        }
        else if (ea.Pointer.Type == PointerType.Touch)
        {
            if (_lastTouchPositions is null)
            {
                base.OnPointerMoved(ea);
                return;
            }

            if (!_lastTouchPositions.ContainsKey(ea.Pointer.Id) && _lastTouchPositions.Count() < 2)
            {
                _lastTouchPositions.Add(ea.Pointer.Id, ea.GetPosition(this));
                base.OnPointerMoved(ea);
                return;
            }

            if (_lastTouchPositions.Count() == 1 && _zoom != 1) // Если есть только одно прикосновение и зум != 1, то токлько перемещение
            {
                var position = ea.GetPosition(this);
                _panX -= (float)(_lastTouchPositions[ea.Pointer.Id].X - position.X);
                _panY -= (float)(_lastTouchPositions[ea.Pointer.Id].Y - position.Y); // Ось Y инвертированна
                _lastTouchPositions[ea.Pointer.Id] = position;
            }
            else if (_lastTouchPositions.Count() == 2) // Если два прикосновения, то перемещение с приближением
            {
                var lastPosition1 = _lastTouchPositions.Skip(0).First().Value;
                var lastPosition2 = _lastTouchPositions.Skip(1).First().Value;
                var lastDistance = Point.Distance(lastPosition1, lastPosition2);
                var lastCenter = PointHelper.Center(lastPosition1, lastPosition2);

                _lastTouchPositions[ea.Pointer.Id] = ea.GetPosition(this);

                var newPosition1 = _lastTouchPositions.Skip(0).First().Value;
                var newPosition2 = _lastTouchPositions.Skip(1).First().Value;
                var newDistance = Point.Distance(newPosition1, newPosition2);
                var newCenter = PointHelper.Center(newPosition1, newPosition2);

                var zoomFactor = newDistance / lastDistance;
                var newZoom = (float)(_zoom * zoomFactor);
                newZoom = (float)Math.Clamp(newZoom, 1f, 10f);

                var imageX = (newCenter.X - Bounds.Width / 2 - _panX) / _zoom;
                var imageY = (newCenter.Y - Bounds.Height / 2 - _panY) / _zoom;

                _zoom = newZoom;

                if (_zoom > 1f)
                {
                    _panX = (float)(newCenter.X - Bounds.Width / 2 - imageX * _zoom);
                    _panY = (float)(newCenter.Y - Bounds.Height / 2 - imageY * _zoom);
                }
                else
                {
                    _zoom = 1f;
                    _panX = 0f;
                    _panY = 0f;
                }
            }
        }
        base.OnPointerMoved(ea);
        InvalidateVisual();
    }

    public override void Render(DrawingContext context)
    {
        context.FillRectangle(new SolidColorBrush(Background), new Rect(0, 0, Bounds.Width, Bounds.Height));
        if (_bitmap is null)
        {
            base.Render(context);
            return;
        }

        var (sx, sy) = ComputeStretchScale(StretchMode, _bitmap.PixelSize.Width, _bitmap.PixelSize.Height);
        sx *= _zoom;
        sy *= _zoom;

        var drawWidth = _bitmap.PixelSize.Width * sx;
        var drawHeight = _bitmap.PixelSize.Height * sy;
        var destRect = new Rect((Bounds.Width - drawWidth) / 2 + _panX, (Bounds.Height - drawHeight) / 2 + _panY, drawWidth, drawHeight);

        var srcRect = ComputeSourceRect(TileMode, _bitmap.PixelSize.Width, _bitmap.PixelSize.Height);

        context.DrawImage(_bitmap, srcRect, destRect);

        base.Render(context);
    }

    private (double sx, double sy) ComputeStretchScale(Stretch stretch, double imageWidth, double imageHeight)
    {
        double viewWidth = Bounds.Width;
        double viewHeight = Bounds.Height;

        var viewAspect = viewWidth / viewHeight;
        var imageAspect = imageWidth / imageHeight;

        switch (stretch)
        {
            case Stretch.None:
                return (1, 1);
            case Stretch.Fill:
                return (viewWidth / imageWidth, viewHeight / imageHeight);
            case Stretch.Uniform:
                if (imageAspect > viewAspect)
                {
                    var s = viewWidth / imageWidth;
                    return (s, s);
                }
                else
                {
                    var s = viewHeight / imageHeight;
                    return (s, s);
                }
            case Stretch.UniformToFill:
                if (imageAspect > viewAspect)
                {
                    var s = viewHeight / imageHeight;
                    return (s, s);
                }
                else
                {
                    var s = viewWidth / imageWidth;
                    return (s, s);
                }
            default:
                return (1, 1);
        }
    }
    private Rect ComputeSourceRect(TileMode mode, int imageWidth, int imageHeight)
    {
        switch (mode)
        {
            case TileMode.None:
                return new Rect(0, 0, imageWidth, imageHeight);
            case TileMode.Tile:
                return new Rect(0, 0, imageWidth * 2, imageHeight * 2);
            case TileMode.FlipX:
                return new Rect(imageWidth, 0, -imageWidth, imageHeight);
            case TileMode.FlipY:
                return new Rect(0, imageHeight, imageWidth, -imageHeight);
            case TileMode.FlipXY:
                return new Rect(imageWidth, imageHeight, -imageWidth, -imageHeight);
            default:
                return new Rect(0, 0, imageWidth, imageHeight);
        }
    }
}