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

import '../models/refuel.dart';
import '../services/session_manager.dart';
import '../widgets/stat_card.dart';
import '../widgets/gas_price_chart.dart';
import '../widgets/consumption_chart.dart';

class HomeScreen extends StatelessWidget {
  const HomeScreen({super.key});

  String _formatDouble(double value) {
    var s = value.toStringAsFixed(2);
    if (s.endsWith('.00')) {
      s = s.substring(0, s.length - 3);
    } else if (s.endsWith('0')) {
      s = s.substring(0, s.length - 1);
    }
    return s;
  }

  double? _allTimeConsumption(List<Refuel> refuels) {
    if (refuels.length < 2) return null;
    final distance = refuels.last.mileage - refuels.first.mileage;
    if (distance <= 0) return null;
    final liters =
        refuels.skip(1).fold<double>(0.0, (sum, r) => sum + r.liters);
    return liters / distance * 100;
  }

  double? _lastConsumption(List<Refuel> refuels) {
    if (refuels.length < 2) return null;
    final last = refuels[refuels.length - 1];
    final prev = refuels[refuels.length - 2];
    final distance = last.mileage - prev.mileage;
    if (distance <= 0) return null;
    return last.liters / distance * 100;
  }

  int? _kmSinceLast(List<Refuel> refuels) {
    if (refuels.length < 2) return null;
    return refuels.last.mileage - refuels[refuels.length - 2].mileage;
  }

  int _kmForPeriod(List<Refuel> refuels, DateTime from) {
    final list = refuels
        .where((r) => r.createdAt != null && r.createdAt!.isAfter(from))
        .toList();
    if (list.length < 2) return 0;
    return list.last.mileage - list.first.mileage;
  }

  int _kmAllTime(List<Refuel> refuels) {
    if (refuels.length < 2) return 0;
    return refuels.last.mileage - refuels.first.mileage;
  }

  @override
  Widget build(BuildContext context) {
    return Consumer<SessionManager>(
      builder: (context, session, _) {
        final vehicle = session.defaultVehicle;
        if (vehicle == null) {
          return const Scaffold(
            body: Center(child: Text('No default vehicle selected')),
          );
        }

        final refuels = session.refuels
            .where((r) => r.vehicleId == vehicle.id)
            .toList();
        refuels.sort((a, b) => a.mileage.compareTo(b.mileage));

        final allCons = _allTimeConsumption(refuels);
        final lastCons = _lastConsumption(refuels);
        final kmLast = _kmSinceLast(refuels);
        final now = DateTime.now();
        final km1m = _kmForPeriod(refuels, now.subtract(const Duration(days: 30)));
        final km6m =
            _kmForPeriod(refuels, now.subtract(const Duration(days: 182)));
        final km1y =
            _kmForPeriod(refuels, now.subtract(const Duration(days: 365)));
        final kmAll = _kmAllTime(refuels);

        final lastRefuels =
            refuels.length > 14 ? refuels.sublist(refuels.length - 14) : refuels;

        return Scaffold(
          body: SafeArea(
            child: SingleChildScrollView(
              child: Padding(
                padding: const EdgeInsets.fromLTRB(16, 16, 16, 32),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                  Card(
                    color: Theme.of(context).colorScheme.secondaryContainer,
                    child: ListTile(
                      leading: const Icon(Icons.directions_car),
                      title: Text(vehicle.name,
                          style: const TextStyle(fontWeight: FontWeight.bold)),
                      subtitle: Text(vehicle.registrationPlate),
                      trailing:
                          const Icon(Icons.star, color: Colors.amber),
                    ),
                  ),
                  const SizedBox(height: 16),
                  const Text('Refuel stats',
                      style:
                          TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
                  const SizedBox(height: 8),
                  GridView.count(
                    shrinkWrap: true,
                    physics: const NeverScrollableScrollPhysics(),
                    crossAxisCount: 2,
                    crossAxisSpacing: 8,
                    mainAxisSpacing: 8,
                    childAspectRatio: 2,
                    children: [
                      StatCard(
                        title: 'Avg consumption (all time)',
                        value: allCons != null
                            ? '${_formatDouble(allCons)} L/100km'
                            : '-',
                      ),
                      StatCard(
                        title: 'Since last refuel',
                        value: lastCons != null
                            ? '${_formatDouble(lastCons)} L/100km'
                            : '-',
                      ),
                    ],
                  ),
                  const SizedBox(height: 24),
                  const Text('Kilometers driven',
                      style:
                          TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
                  Builder(builder: (context) {
                    final kmCards = <Widget>[
                      StatCard(
                        title: 'Since last refuel',
                        value: kmLast != null ? '$kmLast km' : '-',
                      ),
                      StatCard(title: 'Past month', value: '$km1m km'),
                      StatCard(title: 'Past 6 months', value: '$km6m km'),
                      StatCard(title: 'Past year', value: '$km1y km'),
                      StatCard(title: 'All time', value: '$kmAll km'),
                    ];
                    if (kmCards.length.isOdd) {
                      kmCards.add(const SizedBox.shrink());
                    }
                    return GridView.count(
                      shrinkWrap: true,
                      physics: const NeverScrollableScrollPhysics(),
                      crossAxisCount: 2,
                      crossAxisSpacing: 8,
                      mainAxisSpacing: 8,
                      childAspectRatio: 2,
                      children: kmCards,
                    );
                  }),
                  if (lastRefuels.isNotEmpty) ...[
                    const SizedBox(height: 24),
                    Text('Gas price (last ${lastRefuels.length} refuels)',
                        style: const TextStyle(
                            fontSize: 18, fontWeight: FontWeight.bold)),
                    const SizedBox(height: 8),
                    SizedBox(
                      height: 220,
                      child: GasPriceChart(refuels: lastRefuels),
                    ),
                    if (lastRefuels.length > 1) ...[
                      const SizedBox(height: 24),
                      const Text('Consumption trend',
                          style: TextStyle(
                              fontSize: 18, fontWeight: FontWeight.bold)),
                      const SizedBox(height: 8),
                      SizedBox(
                        height: 220,
                        child: ConsumptionChart(refuels: lastRefuels),
                      ),
                    ],
                  ],
                  const SizedBox(height: 8),
                ],
              ),
            ),
          ),
        ),
      );
      },
    );
  }
}