Chessistics/Scripts/Pieces/TrajectView.cs

using Godot;

namespace Chessistics.Scripts.Pieces;

public partial class TrajectView : Line2D
{
    public int PieceId { get; private set; }
    private Polygon2D? _arrowEnd;
    private Polygon2D? _arrowStart;
    private Tween? _pulseTween;
    private Color _baseColor;

    public void Setup(int pieceId, Vector2 from, Vector2 to, Color color)
    {
        PieceId = pieceId;
        _baseColor = color;
        Width = 3f;
        DefaultColor = new Color(color, 0.4f);
        Antialiased = true;
        ClearPoints();
        AddPoint(from);
        AddPoint(to);
        ZIndex = -1;

        _arrowEnd = BuildArrow(from, to, color);
        _arrowStart = BuildArrow(to, from, color);
        AddChild(_arrowEnd);
        AddChild(_arrowStart);

        StartPulse();
    }

    private static Polygon2D BuildArrow(Vector2 from, Vector2 to, Color color)
    {
        var dir = (to - from).Normalized();
        var perp = new Vector2(-dir.Y, dir.X);
        const float arrowSize = 9f;
        var tip = to - dir * 4f;
        var baseL = tip - dir * arrowSize + perp * arrowSize * 0.5f;
        var baseR = tip - dir * arrowSize - perp * arrowSize * 0.5f;
        return new Polygon2D
        {
            Polygon = [tip, baseL, baseR],
            Color = new Color(color, 0.5f)
        };
    }

    private void StartPulse()
    {
        _pulseTween?.Kill();
        _pulseTween = CreateTween();
        _pulseTween.SetLoops();
        _pulseTween.TweenProperty(this, "default_color:a", 0.75f, 1.1f)
            .SetEase(Tween.EaseType.InOut).SetTrans(Tween.TransitionType.Sine);
        _pulseTween.TweenProperty(this, "default_color:a", 0.3f, 1.1f)
            .SetEase(Tween.EaseType.InOut).SetTrans(Tween.TransitionType.Sine);
    }
}