// 当前笔画实时 Painter — 绘制正在绘制中的笔画
//
// 接收可变点缓冲区的直接引用 + 版本号驱动重绘。
// 每帧仅计算当前笔画的轮廓路径，不影响已完成笔画层。
// isComplete: false 让 perfect_freehand 对实时笔尖做端点平滑。

import 'package:flutter/widgets.dart';

import 'stroke_model.dart';
import 'stroke_renderer.dart';

/// 当前笔画实时 Painter
///
/// 由 ListenableBuilder 包裹，监听 ValueNotifier<int> _strokeVersion。
/// 每次 pointer move 递增 version，触发此 Painter 重绘。
/// 仅渲染当前正在绘制的笔画，已完成笔画由 CachedStrokesPainter 处理。
class ActiveStrokePainter extends CustomPainter {
  /// 当前笔画的采样点（直接引用可变缓冲区，不拷贝）
  final List<StrokePoint> points;

  /// 画笔类型
  final BrushType brushType;

  /// 画笔颜色（CSS 十六进制）
  final String color;

  /// 画笔宽度
  final double width;

  /// 版本号，每次 pointer move 递增
  final int version;

  ActiveStrokePainter({
    required this.points,
    required this.brushType,
    required this.color,
    required this.width,
    required this.version,
  });

  @override
  void paint(Canvas canvas, Size size) {
    if (points.length < 2) return;

    // isComplete: false — 实时笔尖不做端点封口，视觉更自然
    final outlinePoints = pointsToOutline(
      points,
      brushType,
      width,
      isComplete: false,
    );
    if (outlinePoints.isEmpty) return;

    final path = buildStrokePath(outlinePoints);

    // 橡皮擦实时反馈：绘制半透明灰色，让用户看到擦除范围
    // 实际擦除在笔画完成后的合成图中通过 BlendMode.dstOut 执行
    if (brushType == BrushType.eraser) {
      canvas.drawPath(path, Paint()
        ..color = const Color(0x40808080) // 25% 灰色
        ..style = PaintingStyle.fill
        ..isAntiAlias = true);
      return;
    }

    // 构造临时 Stroke 用于获取 Paint
    final stroke = Stroke(
      id: '__active__',
      points: points,
      brushType: brushType,
      color: color,
      width: width,
    );
    final paint = createPaintForStroke(stroke);
    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(covariant ActiveStrokePainter oldDelegate) {
    return oldDelegate.version != version;
  }
}