import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:intl/intl.dart';

import '../../../core/router/app_router.dart';
import '../../../core/theme/app_colors.dart';
import '../../machines/data/machine_repository.dart';
import '../../machines/domain/machine_detail.dart';
import '../data/booking_repository.dart';
import '../domain/booking.dart';

/// Modification du créneau d'une réservation existante.
class BookingModifyScreen extends ConsumerStatefulWidget {
  const BookingModifyScreen({super.key, required this.bookingUuid});

  final String bookingUuid;

  @override
  ConsumerState<BookingModifyScreen> createState() => _BookingModifyScreenState();
}

class _BookingModifyScreenState extends ConsumerState<BookingModifyScreen> {
  DateTime? _selectedDate;
  TimeSlot? _selectedSlot;
  bool _isSaving = false;

  Future<void> _confirmMove(Booking booking) async {
    final slot = _selectedSlot;
    if (slot == null) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Sélectionnez un nouveau créneau')),
      );
      return;
    }

    setState(() => _isSaving = true);
    try {
      await ref.read(bookingRepositoryProvider).moveBooking(
            uuid: booking.uuid,
            slotStart: slot.start,
            slotEnd: slot.end,
          );
      ref.invalidate(bookingsProvider);
      ref.invalidate(bookingDetailProvider(booking.uuid));
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(
            content: Text('Créneau modifié avec succès'),
            backgroundColor: AppColors.success,
          ),
        );
        context.go(AppRoutes.bookings);
      }
    } on BookingException catch (e) {
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text(e.message), backgroundColor: AppColors.error),
        );
      }
    } finally {
      if (mounted) setState(() => _isSaving = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final bookingAsync = ref.watch(bookingDetailProvider(widget.bookingUuid));

    return Scaffold(
      backgroundColor: AppColors.background,
      appBar: AppBar(title: const Text('Modifier le créneau')),
      body: bookingAsync.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, __) => const Center(child: Text('Réservation introuvable')),
        data: (booking) {
          if (!booking.canModify) {
            return Center(
              child: Padding(
                padding: const EdgeInsets.all(24),
                child: Text(
                  'Cette réservation ne peut plus être modifiée.',
                  textAlign: TextAlign.center,
                  style: Theme.of(context).textTheme.titleMedium,
                ),
              ),
            );
          }

          final selectedDate = _selectedDate ??
              DateTime(
                booking.slotStart!.year,
                booking.slotStart!.month,
                booking.slotStart!.day,
              );

          final availabilityAsync = ref.watch(
            machineAvailabilityProvider((uuid: booking.machineUuid, date: selectedDate)),
          );

          return Column(
            children: [
              Expanded(
                child: ListView(
                  padding: const EdgeInsets.all(16),
                  children: [
                    Card(
                      child: Padding(
                        padding: const EdgeInsets.all(14),
                        child: Column(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: [
                            Text(booking.machineName, style: Theme.of(context).textTheme.titleMedium),
                            const SizedBox(height: 4),
                            Text(
                              'Créneau actuel',
                              style: Theme.of(context).textTheme.bodyMedium?.copyWith(fontSize: 12),
                            ),
                            Text(
                              booking.slotStart != null && booking.slotEnd != null
                                  ? '${DateFormat('EEEE dd MMM · HH:mm', 'fr_FR').format(booking.slotStart!)} – ${DateFormat('HH:mm').format(booking.slotEnd!)}'
                                  : '—',
                              style: const TextStyle(fontWeight: FontWeight.w600),
                            ),
                          ],
                        ),
                      ),
                    ),
                    const SizedBox(height: 20),
                    Text('Nouveau jour', style: Theme.of(context).textTheme.titleMedium),
                    const SizedBox(height: 10),
                    SizedBox(
                      height: 44,
                      child: ListView.separated(
                        scrollDirection: Axis.horizontal,
                        itemCount: 6,
                        separatorBuilder: (_, __) => const SizedBox(width: 8),
                        itemBuilder: (context, index) {
                          final date = DateTime.now().add(Duration(days: index));
                          final normalized = DateTime(date.year, date.month, date.day);
                          final isSelected = normalized.year == selectedDate.year &&
                              normalized.month == selectedDate.month &&
                              normalized.day == selectedDate.day;

                          return ChoiceChip(
                            label: Text(DateFormat('EEE dd/MM', 'fr_FR').format(normalized)),
                            selected: isSelected,
                            onSelected: (_) => setState(() {
                              _selectedDate = normalized;
                              _selectedSlot = null;
                            }),
                            selectedColor: AppColors.primary.withValues(alpha: 0.15),
                          );
                        },
                      ),
                    ),
                    const SizedBox(height: 20),
                    Text('Nouveau créneau', style: Theme.of(context).textTheme.titleMedium),
                    const SizedBox(height: 12),
                    availabilityAsync.when(
                      loading: () => const Center(child: CircularProgressIndicator()),
                      error: (_, __) => const Text('Impossible de charger les créneaux.'),
                      data: (slots) {
                        if (slots.isEmpty) {
                          return Text(
                            'Aucun créneau disponible ce jour.',
                            style: Theme.of(context).textTheme.bodyMedium,
                          );
                        }
                        return Wrap(
                          spacing: 8,
                          runSpacing: 8,
                          children: slots.map((slot) {
                            final label =
                                '${DateFormat('HH:mm').format(slot.start)} – ${DateFormat('HH:mm').format(slot.end)}';
                            final isSelected = _selectedSlot?.start == slot.start;

                            return FilterChip(
                              label: Text(label),
                              selected: isSelected,
                              onSelected: (_) => setState(() => _selectedSlot = slot),
                              selectedColor: AppColors.primary.withValues(alpha: 0.15),
                              checkmarkColor: AppColors.primary,
                            );
                          }).toList(),
                        );
                      },
                    ),
                  ],
                ),
              ),
              SafeArea(
                child: Padding(
                  padding: const EdgeInsets.fromLTRB(16, 8, 16, 16),
                  child: SizedBox(
                    width: double.infinity,
                    height: 56,
                    child: ElevatedButton.icon(
                      onPressed: _isSaving ? null : () => _confirmMove(booking),
                      style: ElevatedButton.styleFrom(
                        backgroundColor: AppColors.primary,
                        foregroundColor: Colors.white,
                        shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(14)),
                        textStyle: const TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
                      ),
                      icon: _isSaving
                          ? const SizedBox(
                              width: 22,
                              height: 22,
                              child: CircularProgressIndicator(strokeWidth: 2, color: Colors.white),
                            )
                          : const Icon(Icons.check_rounded, size: 24),
                      label: Text(_isSaving ? 'Enregistrement…' : 'Confirmer le changement'),
                    ),
                  ),
                ),
              ),
            ],
          );
        },
      ),
    );
  }
}