import 'dart:math' as math;

import 'package:flutter/material.dart';

import '../theme/theme_x.dart';

/// A single-series trend line — currently just backup-duration history.
/// Hand-rolled `CustomPainter` rather than a charting dependency: one chart
/// in the whole app, a specific visual spec (faint grid, thin line,
/// emphasized endpoint), full control for near-zero cost.
class Sparkline extends StatelessWidget {
  const Sparkline({super.key, required this.values, this.width = 240, this.height = 52});

  final List<double> values;
  final double width;
  final double height;

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      width: width,
      height: height,
      child: CustomPaint(
        painter: _SparklinePainter(
          values: values,
          lineColor: context.colors.primary,
          gridColor: context.colors.outlineVariant,
        ),
      ),
    );
  }
}

class _SparklinePainter extends CustomPainter {
  _SparklinePainter({required this.values, required this.lineColor, required this.gridColor});

  final List<double> values;
  final Color lineColor;
  final Color gridColor;

  static const _topPad = 6.0;
  static const _bottomPad = 6.0;

  @override
  void paint(Canvas canvas, Size size) {
    if (values.isEmpty) return;

    final minV = values.reduce(math.min);
    final maxV = values.reduce(math.max);
    final range = (maxV - minV).abs() < 1e-9 ? 1.0 : maxV - minV;
    final plotHeight = size.height - _topPad - _bottomPad;

    final gridPaint = Paint()
      ..color = gridColor
      ..strokeWidth = 1;
    canvas.drawLine(Offset(0, _topPad), Offset(size.width, _topPad), gridPaint);
    canvas.drawLine(
      Offset(0, size.height - _bottomPad),
      Offset(size.width, size.height - _bottomPad),
      gridPaint,
    );

    if (values.length == 1) {
      final y = _topPad + plotHeight / 2;
      canvas.drawCircle(Offset(size.width, y), 3.4, Paint()..color = lineColor);
      return;
    }

    final dx = size.width / (values.length - 1);
    final points = [
      for (var i = 0; i < values.length; i++)
        Offset(i * dx, _topPad + plotHeight - ((values[i] - minV) / range) * plotHeight),
    ];

    final fillPath = Path()..moveTo(points.first.dx, size.height - _bottomPad);
    for (final p in points) {
      fillPath.lineTo(p.dx, p.dy);
    }
    fillPath
      ..lineTo(points.last.dx, size.height - _bottomPad)
      ..close();
    canvas.drawPath(fillPath, Paint()..color = lineColor.withValues(alpha: 0.14));

    final linePath = Path()..moveTo(points.first.dx, points.first.dy);
    for (final p in points.skip(1)) {
      linePath.lineTo(p.dx, p.dy);
    }
    canvas.drawPath(
      linePath,
      Paint()
        ..color = lineColor
        ..style = PaintingStyle.stroke
        ..strokeWidth = 2
        ..strokeCap = StrokeCap.round
        ..strokeJoin = StrokeJoin.round,
    );

    canvas.drawCircle(points.last, 3.4, Paint()..color = lineColor);
  }

  @override
  bool shouldRepaint(covariant _SparklinePainter oldDelegate) =>
      oldDelegate.values != values ||
      oldDelegate.lineColor != lineColor ||
      oldDelegate.gridColor != gridColor;
}