import 'package:fl_chart/fl_chart.dart';
import 'package:flutter/material.dart';
import 'package:intl/intl.dart' as intl;
import 'dart:math';

import '../model/reading.dart';

class ReadingGraph extends StatelessWidget {
  const ReadingGraph({super.key, required List<Reading> readings})
      : _readings = readings;
  final List<Reading> _readings;

  @override
  Widget build(BuildContext context) {
    if (_readings.isEmpty) {
      return Text('No readings on record.');
    }

    final spots = _readings
        .map<FlSpot>(
          (e) => FlSpot(
              e.dateTime.millisecondsSinceEpoch.toDouble() / 1000 / 60,
              e.value),
        )
        .toList();

    return LineChart(
      LineChartData(
        maxY: _readings.map<double>((e) => e.value).reduce(max) + 0.05,
        minY: _readings.map<double>((e) => e.value).reduce(min) - 0.05,
        lineBarsData: [
          LineChartBarData(
            isCurved: true,
            color: Colors.cyan,
            barWidth: 2,
            isStrokeCapRound: true,
            dotData: const FlDotData(show: false),
            spots: _readings
                .map<FlSpot>(
                  (e) => FlSpot(
                      e.dateTime.millisecondsSinceEpoch.toDouble() / 1000 / 60,
                      e.value),
                )
                .toList(),
          )
        ],
        titlesData: FlTitlesData(
          bottomTitles: getBottomTitles(spots),
          topTitles: const AxisTitles(sideTitles: SideTitles()),
          rightTitles: const AxisTitles(sideTitles: SideTitles()),
        ),
      ),
    );
  }

  AxisTitles getBottomTitles(List<FlSpot> spots) {
    final maxX = double.parse(
        spots.map<double>((e) => (e.x)).reduce(max).toStringAsFixed(0));
    final minX = double.parse(
        spots.map<double>((e) => e.x).reduce(min).toStringAsFixed(0));
    final middle =
        double.parse(spots[spots.length ~/ 2].x.toStringAsFixed(0)) + 4;

    return AxisTitles(
      sideTitles: SideTitles(
        interval: 1,
        showTitles: true,
        getTitlesWidget: (value, meta) {
          String text = '';
          if (value == maxX) {
            text = getDate(spots.first.x);
          } else if (double.parse(value.toStringAsFixed(0)) == minX) {
            text = getDate(spots.last.x);
          } else if (value == middle) {
            text = getDate(middle);
          }
          return Text(text);
        },
      ),
    );
  }

  String getDate(double value) {
    intl.DateFormat hmFormat = intl.DateFormat('Hm');
    return hmFormat.format(
        DateTime.fromMillisecondsSinceEpoch((value * 1000 * 60).toInt()));
  }
}