import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:mileograph_flutter/objects/objects.dart';
import 'package:mileograph_flutter/services/data_service.dart';
import 'package:provider/provider.dart';

class StatsPage extends StatefulWidget {
  const StatsPage({super.key});

  @override
  State<StatsPage> createState() => _StatsPageState();
}

class _StatsPageState extends State<StatsPage> {
  final NumberFormat _mileageFormat = NumberFormat('#,##0.##');
  final NumberFormat _countFormat = NumberFormat.decimalPattern();

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _loadStats();
    });
  }

  Future<void> _loadStats({bool force = false}) {
    return context.read<DataService>().fetchAboutStats(force: force);
  }

  @override
  Widget build(BuildContext context) {
    final data = context.watch<DataService>();
    return Scaffold(
      appBar: AppBar(title: const Text('Stats')),
      body: RefreshIndicator(
        onRefresh: () => _loadStats(force: true),
        child: _buildContent(data),
      ),
    );
  }

  Widget _buildContent(DataService data) {
    final stats = data.aboutStats;
    final loading = data.isAboutStatsLoading;

    if (loading && stats == null) {
      return ListView(
        physics: const AlwaysScrollableScrollPhysics(),
        children: const [
          SizedBox(height: 140),
          Center(child: CircularProgressIndicator()),
          SizedBox(height: 140),
        ],
      );
    }

    if (stats == null || stats.sortedYears.isEmpty) {
      return ListView(
        physics: const AlwaysScrollableScrollPhysics(),
        padding: const EdgeInsets.all(24),
        children: [
          const SizedBox(height: 40),
          const Center(child: Text('No stats available yet.')),
          const SizedBox(height: 12),
          Center(
            child: OutlinedButton(
              onPressed: () => _loadStats(force: true),
              child: const Text('Retry'),
            ),
          ),
        ],
      );
    }

    final years = stats.sortedYears;
    return ListView.builder(
      padding: const EdgeInsets.all(16),
      itemCount: years.length,
      itemBuilder: (context, index) {
        return Padding(
          padding: EdgeInsets.only(bottom: index == years.length - 1 ? 0 : 12),
          child: _buildYearCard(context, years[index]),
        );
      },
    );
  }

  Widget _buildYearCard(BuildContext context, StatsYear year) {
    final theme = Theme.of(context);
    return Card(
      child: Padding(
        padding: const EdgeInsets.all(12),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  year.year.toString(),
                  style: theme.textTheme.titleLarge,
                ),
                const Spacer(),
                Wrap(
                  spacing: 8,
                  runSpacing: 8,
                  alignment: WrapAlignment.end,
                  children: [
                    _buildInfoChip(
                      context,
                      label: 'Mileage',
                      value: '${_mileageFormat.format(year.mileage)} mi',
                    ),
                    _buildInfoChip(
                      context,
                      label: 'Winners',
                      value: _countFormat.format(year.winnerCount),
                    ),
                  ],
                ),
              ],
            ),
            const SizedBox(height: 8),
            _buildSection<StatsClassMileage>(
              context,
              title: 'Top classes',
              items: year.topClasses,
              emptyLabel: 'No class data',
              itemBuilder: (item, index) => ListTile(
                dense: true,
                contentPadding: const EdgeInsets.symmetric(horizontal: 8),
                title: Text(item.locoClass),
                trailing: Text('${_mileageFormat.format(item.mileage)} mi'),
              ),
            ),
            _buildSection<StatsNetworkMileage>(
              context,
              title: 'Top networks',
              items: year.topNetworks,
              emptyLabel: 'No network data',
              itemBuilder: (item, index) => ListTile(
                dense: true,
                contentPadding: const EdgeInsets.symmetric(horizontal: 8),
                title: Text(item.network),
                trailing: Text('${_mileageFormat.format(item.mileage)} mi'),
              ),
            ),
            _buildSection<StatsStationVisits>(
              context,
              title: 'Top stations',
              items: year.topStations,
              emptyLabel: 'No station data',
              itemBuilder: (item, index) => ListTile(
                dense: true,
                contentPadding: const EdgeInsets.symmetric(horizontal: 8),
                title: Text(item.station),
                trailing: Text(
                  '${_countFormat.format(item.visits)} visit${item.visits == 1 ? '' : 's'}',
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildInfoChip(BuildContext context,
      {required String label, required String value}) {
    final theme = Theme.of(context);
    return Chip(
      padding: const EdgeInsets.symmetric(horizontal: 8),
      label: Text(
        '$label: $value',
        style: theme.textTheme.labelLarge,
      ),
    );
  }

  Widget _buildSection<T>(
    BuildContext context, {
    required String title,
    required List<T> items,
    required Widget Function(T item, int index) itemBuilder,
    String emptyLabel = 'No data',
  }) {
    final theme = Theme.of(context);
    return Padding(
      padding: const EdgeInsets.only(top: 4),
      child: ExpansionTile(
        tilePadding: const EdgeInsets.symmetric(horizontal: 8),
        childrenPadding:
            const EdgeInsets.only(left: 8, right: 8, bottom: 8),
        title: Text(
          title,
          style: theme.textTheme.titleMedium,
        ),
        children: items.isEmpty
            ? [
                Padding(
                  padding: const EdgeInsets.symmetric(vertical: 8),
                  child: Text(
                    emptyLabel,
                    style: theme.textTheme.bodySmall,
                  ),
                ),
              ]
            : items
                .asMap()
                .entries
                .map((entry) => itemBuilder(entry.value, entry.key))
                .toList(),
      ),
    );
  }
}