import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';

import '../../../models/health.dart';

/// 体重折线图（含理想目标线）。
///
/// 和 `donut_chart.dart` 一个纪律：**fl_chart 的类型只出现在这个文件里**。
/// 页面只传数据进来，升级图表库时只需要改这一处。
///
/// 两条线：
///   · 实测体重（实线，圆点）
///   · 理想体重（虚线，来自目标）—— 一眼看出「落后了还是超前了」
class WeightLineChart extends StatelessWidget {
  const WeightLineChart({
    super.key,
    required this.points,
    this.idealCurve = const [],
    this.height = 220,
  });

  /// 实测体重点（按日期升序）
  final List<WeightPoint> points;

  /// 理想体重曲线，为空就不画
  final List<WeightPoint> idealCurve;

  final double height;

  @override
  Widget build(BuildContext context) {
    if (points.isEmpty) {
      return SizedBox(
        height: height,
        child: const Center(
          child: Text(
            '还没有体重记录',
            style: TextStyle(fontSize: 13, color: Color(0xFFBCAAA4)),
          ),
        ),
      );
    }

    // X 轴用「距首日天数」而不是时间戳：时间戳在 fl_chart 里是毫秒级的大数，
    // 坐标轴标签会很难格式化，换算成天数后间隔和标签都很直观。
    final base = points.first.date;
    double dayOf(DateTime d) => d.difference(base).inDays.toDouble();

    final actual = points
        .map((p) => FlSpot(dayOf(p.date), p.weight))
        .toList(growable: false);

    // 理想曲线的起点可能早于实测（比如先设目标后开始记体重），
    // 所以基准日要取两者更早的那个，否则理想线会被挤到左边界外
    final ideal = <FlSpot>[];
    for (final p in idealCurve) {
      final x = dayOf(p.date);
      // 只画在实测数据的可见区间内，避免 X 轴被拉得过长
      if (x >= 0 && x <= dayOf(points.last.date)) {
        ideal.add(FlSpot(x, p.weight));
      }
    }

    final (minY, maxY) = _yRange(actual, ideal);
    final maxX = dayOf(points.last.date);

    return SizedBox(
      height: height,
      child: LineChart(
        LineChartData(
          minX: 0,
          maxX: maxX <= 0 ? 1 : maxX,
          minY: minY,
          maxY: maxY,
          gridData: FlGridData(
            show: true,
            drawVerticalLine: false,
            horizontalInterval: ((maxY - minY) / 4).clamp(0.5, 100),
            getDrawingHorizontalLine: (_) => const FlLine(
              color: Color(0xFFF0EAE4),
              strokeWidth: 1,
            ),
          ),
          borderData: FlBorderData(show: false),
          titlesData: FlTitlesData(
            topTitles: const AxisTitles(),
            rightTitles: const AxisTitles(),
            leftTitles: AxisTitles(
              sideTitles: SideTitles(
                showTitles: true,
                reservedSize: 40,
                interval: ((maxY - minY) / 4).clamp(0.5, 100),
                getTitlesWidget: (value, meta) => Text(
                  value.toStringAsFixed(1),
                  style: const TextStyle(
                      fontSize: 10.5, color: Color(0xFFBCAAA4)),
                ),
              ),
            ),
            bottomTitles: AxisTitles(
              sideTitles: SideTitles(
                showTitles: true,
                reservedSize: 26,
                // 最多标 4 个日期，再多会挤成一团
                interval: maxX <= 0 ? 1 : (maxX / 3).ceilToDouble(),
                getTitlesWidget: (value, meta) {
                  final date = base.add(Duration(days: value.round()));
                  return Padding(
                    padding: const EdgeInsets.only(top: 6),
                    child: Text(
                      '${date.month}-${date.day}',
                      style: const TextStyle(
                          fontSize: 10.5, color: Color(0xFFBCAAA4)),
                    ),
                  );
                },
              ),
            ),
          ),
          lineTouchData: LineTouchData(
            touchTooltipData: LineTouchTooltipData(
              getTooltipColor: (_) => const Color(0xFF5D4037),
              getTooltipItems: (spots) => spots.map((spot) {
                final date = base.add(Duration(days: spot.x.round()));
                return LineTooltipItem(
                  '${date.month}月${date.day}日\n${spot.y.toStringAsFixed(1)} kg',
                  const TextStyle(
                      color: Colors.white, fontSize: 12, height: 1.5),
                );
              }).toList(),
            ),
          ),
          lineBarsData: [
            // 实测：实线 + 圆点
            LineChartBarData(
              spots: actual,
              isCurved: true,
              curveSmoothness: 0.25,
              preventCurveOverShooting: true,
              color: const Color(0xFFC8956E),
              barWidth: 2.6,
              isStrokeCapRound: true,
              dotData: FlDotData(
                // 点多了就不画圆点，否则整条线会变成一串珠子
                show: actual.length <= 20,
                getDotPainter: (spot, percent, bar, index) =>
                    FlDotCirclePainter(
                  radius: 3,
                  color: Colors.white,
                  strokeWidth: 2,
                  strokeColor: const Color(0xFFC8956E),
                ),
              ),
              belowBarData: BarAreaData(
                show: true,
                color: const Color(0xFFC8956E).withValues(alpha: 0.1),
              ),
            ),
            // 理想：虚线、不带点 —— 视觉上明确区分「这是参照不是实测」
            if (ideal.length >= 2)
              LineChartBarData(
                spots: ideal,
                isCurved: false,
                color: const Color(0xFF4FA98A),
                barWidth: 1.6,
                dashArray: const [5, 4],
                dotData: const FlDotData(show: false),
              ),
          ],
        ),
      ),
    );
  }

  /// Y 轴范围：把实测点和理想线都包进来，上下各留 10% 余量。
  ///
  /// 余量是必要的 —— 贴着边框的线看不出趋势，而且圆点会被裁掉半个。
  (double, double) _yRange(List<FlSpot> actual, List<FlSpot> ideal) {
    final values = <double>[
      ...actual.map((s) => s.y),
      ...ideal.map((s) => s.y),
    ];
    if (values.isEmpty) return (0, 100);

    var min = values.first;
    var max = values.first;
    for (final v in values) {
      if (v < min) min = v;
      if (v > max) max = v;
    }

    // 所有点都一样重（用户连着记了几天同一个数）时给一个固定跨度，
    // 否则 maxY == minY 会让图表算出 NaN
    if ((max - min).abs() < 0.1) {
      return (min - 1, max + 1);
    }
    final pad = (max - min) * 0.1;
    return (min - pad, max + pad);
  }
}