import 'package:flutter/material.dart';

class CanvasRuler extends StatelessWidget {
  final double lengthMm;
  final double scale; // pixels per mm
  final bool isHorizontal;
  final double thickness;

  const CanvasRuler({
    super.key,
    required this.lengthMm,
    required this.scale,
    this.isHorizontal = true,
    this.thickness = 20.0,
  });

  @override
  Widget build(BuildContext context) {
    final isDark = Theme.of(context).brightness == Brightness.dark;
    return CustomPaint(
      size: isHorizontal
          ? Size(lengthMm * scale, thickness)
          : Size(thickness, lengthMm * scale),
      painter: _RulerPainter(
        lengthMm: lengthMm,
        scale: scale,
        isHorizontal: isHorizontal,
        isDark: isDark,
      ),
    );
  }
}

class _RulerPainter extends CustomPainter {
  final double lengthMm;
  final double scale;
  final bool isHorizontal;
  final bool isDark;

  _RulerPainter({
    required this.lengthMm,
    required this.scale,
    required this.isHorizontal,
    required this.isDark,
  });

  @override
  void paint(Canvas canvas, Size size) {
    final bgPaint = Paint()
      ..color = isDark ? const Color(0xFF1E293B) : const Color(0xFFF1F5F9);
    canvas.drawRect(Offset.zero & size, bgPaint);

    final linePaint = Paint()
      ..color = isDark ? Colors.white30 : Colors.black26
      ..strokeWidth = 1.0;

    final textStyle = TextStyle(
      color: isDark ? Colors.white60 : Colors.black54,
      fontSize: 8,
      fontWeight: FontWeight.w500,
    );

    final textPainter = TextPainter(
      textDirection: TextDirection.ltr,
    );

    // Draw ticks every 1mm, with labels every 5mm or 10mm
    for (int mm = 0; mm <= lengthMm.ceil(); mm++) {
      final pos = mm * scale;
      final isTen = mm % 10 == 0;
      final isFive = mm % 5 == 0;

      final tickLength = isTen ? 12.0 : (isFive ? 7.0 : 4.0);

      if (isHorizontal) {
        canvas.drawLine(
          Offset(pos, size.height - tickLength),
          Offset(pos, size.height),
          linePaint,
        );

        if (isTen && mm > 0 && mm < lengthMm) {
          textPainter.text = TextSpan(text: '$mm', style: textStyle);
          textPainter.layout();
          textPainter.paint(canvas, Offset(pos - (textPainter.width / 2), 2));
        }
      } else {
        canvas.drawLine(
          Offset(size.width - tickLength, pos),
          Offset(size.width, pos),
          linePaint,
        );

        if (isTen && mm > 0 && mm < lengthMm) {
          textPainter.text = TextSpan(text: '$mm', style: textStyle);
          textPainter.layout();
          textPainter.paint(canvas, Offset(2, pos - (textPainter.height / 2)));
        }
      }
    }
  }

  @override
  bool shouldRepaint(covariant _RulerPainter oldDelegate) {
    return oldDelegate.lengthMm != lengthMm ||
        oldDelegate.scale != scale ||
        oldDelegate.isHorizontal != isHorizontal ||
        oldDelegate.isDark != isDark;
  }
}