using Avalonia;
using Avalonia.Controls;
using Avalonia.Media;
using Avalonia.VisualTree;


namespace Plugin.Cowain.Wcs.Controls;

public class RgvArrowDecorator : Decorator
{
    public static readonly StyledProperty<Point> ArrowEndCanvasPointProperty =
        AvaloniaProperty.Register<RgvArrowDecorator, Point>(nameof(ArrowEndCanvasPoint));

    public Point ArrowEndCanvasPoint
    {
        get => GetValue(ArrowEndCanvasPointProperty);
        set => SetValue(ArrowEndCanvasPointProperty, value);
    }

    public static readonly StyledProperty<IBrush> ArrowBrushProperty =
        AvaloniaProperty.Register<RgvArrowDecorator, IBrush>(nameof(ArrowBrush), Brushes.Red);

    public IBrush ArrowBrush
    {
        get => GetValue(ArrowBrushProperty);
        set => SetValue(ArrowBrushProperty, value);
    }

    public static readonly StyledProperty<bool> ArrowDirectionProperty =
      AvaloniaProperty.Register<RgvArrowDecorator, bool>(nameof(ArrowDirection), false);

    public bool ArrowDirection
    {
        get => GetValue(ArrowDirectionProperty);
        set => SetValue(ArrowDirectionProperty, value);
    }

    public RgvArrowDecorator()
    {
        this.LayoutUpdated += (s, e) => this.InvalidateVisual();
        ArrowEndCanvasPointProperty.Changed.AddClassHandler<RgvArrowDecorator>((b, e) => b.InvalidateVisual());
        ArrowBrushProperty.Changed.AddClassHandler<RgvArrowDecorator>((b, e) => b.InvalidateVisual());
        ArrowDirectionProperty.Changed.AddClassHandler<RgvArrowDecorator>((b, e) => b.InvalidateVisual());
    }


    public override void Render(DrawingContext context)
    {
        base.Render(context);

        var start = new Point(Bounds.Width / 2, Bounds.Height / 2);
        var endCanvas = ArrowEndCanvasPoint;

        var canvas = this.FindAncestorOfType<Canvas>();
        if (canvas == null)
            return;

        var transform = this.TransformToVisual(canvas);
        Point myLeftTop = default;
        if (transform != null)
        {
            if (transform is Matrix matrix)
                myLeftTop = matrix.Transform(new Point(0, 0));
        }

        // 转换为本地坐标
        var end = new Point(endCanvas.X - myLeftTop.X, endCanvas.Y - myLeftTop.Y);

        // 计算三段折线
        double offset = 15; // 垂直偏移
        bool isAbove = end.Y < start.Y;

        // 第一拐点：起点垂直偏移
        var first = new Point(start.X, start.Y + (isAbove ? -offset : offset));
        // 第二拐点：目标X，起点Y偏移
        var second = new Point(end.X, end.Y + (isAbove ? offset : -offset));
        // 终点：目标点
        var last = new Point(end.X, end.Y);

        // 画三段折线
        var pen = new Pen(ArrowBrush, 2);
        context.DrawLine(pen, start, first);
        context.DrawLine(pen, first, second);
        context.DrawLine(pen, second, last);

        // 画箭头头部
        if (ArrowDirection)
        {
            DrawArrowHead(context, end, second, ArrowBrush);
        }
        else
        {
            DrawArrowHead(context, second, end, ArrowBrush);
        }
      
    }

    private void DrawArrowHead(DrawingContext context, Point from, Point to, IBrush brush)
    {
        // 箭头头部为V型
        double arrowSize = 10;
        double angle = Math.Atan2(to.Y - from.Y, to.X - from.X);
        double leftAngle = angle + Math.PI / 6;
        double rightAngle = angle - Math.PI / 6;

        var left = new Point(
            to.X - arrowSize * Math.Cos(leftAngle),
            to.Y - arrowSize * Math.Sin(leftAngle));
        var right = new Point(
            to.X - arrowSize * Math.Cos(rightAngle),
            to.Y - arrowSize * Math.Sin(rightAngle));

        var pen = new Pen(brush, 2);
        context.DrawLine(pen, to, left);
        context.DrawLine(pen, to, right);
    }
}