chinese_chess/Scripts/Entities/ChessBoard.cs

// Chessboard.cs
using System;
using Godot;
using ChineseChess;
using Godot.Collections;

using static IBoard;
public partial class ChessBoard : Node2D, ICCBoardOn {
    public event EventHandler<Vector2>? OnMouseClicked;
	public event EventHandler<Vector2>? OnPosClicked;
	public event EventHandler<int>? OnStepsChanged;

	public Vector2 from = Vector2.Inf, to = Vector2.Inf;
	public Array<Vector2> canMovePos = [];

	public override void _Ready() {
	}

	public void Clear() {
		from = to = Vector2.Inf;
		QueueRedraw();
	}

	void IBoardOn.OnInsert(object self, IPiece piece) {
		ChessPiece? node = piece.On as ChessPiece;
        // throw new InvalidOperationException();
        node ??= new ChessPiece((CCPiece)piece);
		node.ShowBehindParent = true;
        AddChild(node);

			// ChessPiece chessPiece = null;
			// if (piece.Data.TryGetValue("Godot", out object node)) {
			// 	chessPiece = node as ChessPiece;
			// } else {
			// 	chessPiece = new((CCPiece)piece);
			// }
			// chessPiece.ShowBehindParent = true;
			// AddChild(chessPiece);
	}

	void IBoardOn.OnRemove(object self, IPiece piece) {
		if (piece.On is not ChessPiece node) {
			throw new InvalidOperationException();
		}
		RemoveChild(node);
	}

	void IBoardOn.OnMove(object self, IBoardOn.MoveEventArgs vals) {
		from = PosTrans.transArrToPix * new Vector2(vals.From.X, vals.From.Y);
		to = PosTrans.transArrToPix * new Vector2(vals.To.X, vals.To.Y);
		QueueRedraw();
	}

	void ICCBoardOn.OnSteps(object _self, int oldSteps) {
		if (_self is not CCBoard self) return;
		OnStepsChanged?.Invoke(self, self.Steps);
	}

	public override void _Draw() {
		Color color = new(0.7f, 0.7f, 0.7f, 0.5f);
		DrawLine(from, to, color, PosTrans.pixGripSize / 5);
		DrawCircle(from, PosTrans.pixGripSize / 2.2f, color);
		foreach (Vector2 pos in canMovePos) {
			DrawCircle(pos, PosTrans.pixGripSize / 2.2f,
				 color.Inverted());
		}
    }

    public override void _Input(InputEvent @event) {
		if (@event is InputEventMouseButton mouseEvent &&
				mouseEvent.Pressed &&
				mouseEvent.ButtonIndex == MouseButton.Left) {
            OnMouseClicked?.Invoke(this, GetLocalMousePosition());
			OnPosClicked?.Invoke(this, (PosTrans.transArrToPix.AffineInverse() *
				GetLocalMousePosition()).Round());
		}
	}

	public static class PosTrans {
		public static readonly int pixGripSize = 32;
		public static readonly Transform2D transArrToPix = new(
			new Vector2(pixGripSize, 0),
			new Vector2(0, pixGripSize),
			new Vector2(-4, -4.5f) * pixGripSize
		);
	}
}