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

import 'package:hl_lieferservice/domain/entity/payment_method.dart';
import 'package:hl_lieferservice/feature/delivery/detail/model/delivery_payment_status.dart';
import 'package:hl_lieferservice/feature/delivery/detail/presentation/widget/payment_method_icon.dart';
import 'package:hl_lieferservice/feature/delivery/detail/presentation/widget/reason_dialog.dart';
import 'package:hl_lieferservice/feature/payment_methods/bloc/payment_methods_cubit.dart';

/// Ergebnis des Zahlungs-Modals. `null` = abgebrochen, nichts passiert.
sealed class PaymentSheetResult {
  const PaymentSheetResult();
}

/// Der Fahrer hat bestätigt, dass die Zahlung per [method] erhalten wurde
/// (bzw. bei „Rechnung": dass auf Rechnung abgewickelt wird).
class PaymentConfirmed extends PaymentSheetResult {
  const PaymentConfirmed(this.method);
  final PaymentMethod method;
}

/// Zahlung ist nicht möglich — die ganze Lieferung soll abgebrochen werden.
class DeliveryCancelRequested extends PaymentSheetResult {
  const DeliveryCancelRequested(this.reason);
  final String reason;
}

/// Öffnet das Zahlungs-Modal.
///
/// Zeigt groß den offenen Betrag, die Zahlungsmethoden als Cards (dynamisch
/// aus den Backend-Stammdaten) und bei EC-Karte groß die Kundennummer, die
/// der Fahrer am EC-Gerät eingibt. Schließt sich nur über „Abbrechen",
/// „Zahlung erhalten" oder „Lieferung abbrechen".
Future<PaymentSheetResult?> showPaymentSheet(
  BuildContext context, {
  required int openCents,
  required int customerNumber,
  required String? preselectedMethodId,
}) {
  return showModalBottomSheet<PaymentSheetResult>(
    context: context,
    isScrollControlled: true,
    useSafeArea: true,
    // Kein versehentliches Wegwischen: Das Modal endet nur über die Buttons.
    isDismissible: false,
    enableDrag: false,
    showDragHandle: false,
    builder:
        (_) => _PaymentSheet(
          openCents: openCents,
          customerNumber: customerNumber,
          preselectedMethodId: preselectedMethodId,
        ),
  );
}

class _PaymentSheet extends StatefulWidget {
  const _PaymentSheet({
    required this.openCents,
    required this.customerNumber,
    required this.preselectedMethodId,
  });

  final int openCents;
  final int customerNumber;
  final String? preselectedMethodId;

  @override
  State<_PaymentSheet> createState() => _PaymentSheetState();
}

class _PaymentSheetState extends State<_PaymentSheet> {
  String? _selectedId;

  @override
  void initState() {
    super.initState();
    // Vorauswahl = am Beleg hinterlegte Methode. Der Fahrer kann wechseln.
    _selectedId = widget.preselectedMethodId;
  }

  Future<void> _cancelDelivery() async {
    final navigator = Navigator.of(context);
    final reason = await showReasonDialog(context, 'Lieferung abbrechen');
    if (reason == null || !mounted) return;
    navigator.pop(DeliveryCancelRequested(reason));
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return BlocBuilder<PaymentMethodsCubit, PaymentMethodsState>(
      builder: (context, pmState) {
        final methods =
            pmState is PaymentMethodsLoaded
                ? pmState.methods.where((m) => m.active).toList()
                : const <PaymentMethod>[];
        PaymentMethod? selected;
        for (final m in methods) {
          if (m.id == _selectedId) selected = m;
        }
        final isInvoice = selected?.code == 'invoice';

        return Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Flexible(
              child: ListView(
                shrinkWrap: true,
                padding: const EdgeInsets.fromLTRB(20, 20, 20, 8),
                children: [
                  Text(
                    'Zahlung abwickeln',
                    style: theme.textTheme.titleLarge?.copyWith(
                      fontWeight: FontWeight.w700,
                    ),
                  ),
                  const SizedBox(height: 16),
                  _AmountBanner(openCents: widget.openCents),
                  const SizedBox(height: 20),
                  Text(
                    'Zahlungsart',
                    style: theme.textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.w700,
                    ),
                  ),
                  const SizedBox(height: 8),
                  ..._methodSection(context, pmState, methods),
                  if (selected != null) ...[
                    const SizedBox(height: 8),
                    _MethodHint(
                      method: selected,
                      customerNumber: widget.customerNumber,
                    ),
                  ],
                ],
              ),
            ),
            SafeArea(
              top: false,
              child: Padding(
                padding: const EdgeInsets.fromLTRB(20, 8, 20, 12),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    FilledButton.icon(
                      style: FilledButton.styleFrom(
                        minimumSize: const Size.fromHeight(60),
                        textStyle: const TextStyle(
                          fontSize: 18,
                          fontWeight: FontWeight.w700,
                        ),
                      ),
                      onPressed:
                          selected == null
                              ? null
                              : () => Navigator.of(
                                context,
                              ).pop(PaymentConfirmed(selected!)),
                      icon: const Icon(Icons.check_circle_outline),
                      label: Text(
                        isInvoice
                            ? 'Auf Rechnung bestätigen'
                            : 'Zahlung erhalten',
                      ),
                    ),
                    const SizedBox(height: 8),
                    Row(
                      children: [
                        Expanded(
                          flex: 3,
                          child: OutlinedButton.icon(
                            style: OutlinedButton.styleFrom(
                              minimumSize: const Size.fromHeight(48),
                              padding: const EdgeInsets.symmetric(
                                horizontal: 12,
                              ),
                              foregroundColor: theme.colorScheme.error,
                              side: BorderSide(color: theme.colorScheme.error),
                            ),
                            onPressed: _cancelDelivery,
                            icon: const Icon(Icons.block),
                            label: const Text('Lieferung abbrechen'),
                          ),
                        ),
                        const SizedBox(width: 12),
                        Expanded(
                          flex: 2,
                          child: TextButton(
                            style: TextButton.styleFrom(
                              minimumSize: const Size.fromHeight(48),
                            ),
                            onPressed: () => Navigator.of(context).pop(),
                            child: const Text('Abbrechen'),
                          ),
                        ),
                      ],
                    ),
                  ],
                ),
              ),
            ),
          ],
        );
      },
    );
  }

  List<Widget> _methodSection(
    BuildContext context,
    PaymentMethodsState state,
    List<PaymentMethod> methods,
  ) {
    if (state is PaymentMethodsFailed) {
      return [
        Card(
          margin: EdgeInsets.zero,
          color: Theme.of(context).colorScheme.errorContainer,
          child: ListTile(
            title: Text(state.message),
            trailing: TextButton.icon(
              onPressed: () => context.read<PaymentMethodsCubit>().load(),
              icon: const Icon(Icons.refresh),
              label: const Text('Erneut laden'),
            ),
          ),
        ),
      ];
    }
    if (state is! PaymentMethodsLoaded) {
      return const [
        Padding(
          padding: EdgeInsets.all(16),
          child: Center(child: CircularProgressIndicator()),
        ),
      ];
    }
    if (methods.isEmpty) {
      return const [Text('Keine Zahlungsmethoden hinterlegt.')];
    }
    return [
      for (final m in methods)
        _MethodCard(
          method: m,
          selected: m.id == _selectedId,
          onTap: () => setState(() => _selectedId = m.id),
        ),
    ];
  }
}

/// Der zu zahlende Betrag, bewusst sehr groß.
class _AmountBanner extends StatelessWidget {
  const _AmountBanner({required this.openCents});

  final int openCents;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final primary = theme.colorScheme.primary;
    return Container(
      padding: const EdgeInsets.symmetric(vertical: 18, horizontal: 16),
      decoration: BoxDecoration(
        color: primary.withValues(alpha: 0.08),
        borderRadius: BorderRadius.circular(16),
        border: Border.all(color: primary.withValues(alpha: 0.35)),
      ),
      child: Column(
        children: [
          Text('Noch zu zahlen', style: theme.textTheme.titleSmall),
          const SizedBox(height: 4),
          FittedBox(
            fit: BoxFit.scaleDown,
            child: Text(
              formatEuroCents(openCents),
              style: theme.textTheme.displayMedium?.copyWith(
                fontWeight: FontWeight.w800,
                color: primary,
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _MethodCard extends StatelessWidget {
  const _MethodCard({
    required this.method,
    required this.selected,
    required this.onTap,
  });

  final PaymentMethod method;
  final bool selected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final scheme = Theme.of(context).colorScheme;
    return Card(
      margin: const EdgeInsets.only(bottom: 10),
      clipBehavior: Clip.antiAlias,
      elevation: selected ? 2 : 0,
      color: selected ? scheme.primaryContainer : scheme.surface,
      surfaceTintColor: Colors.transparent,
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(14),
        side: BorderSide(
          color: selected ? scheme.primary : scheme.outlineVariant,
          width: selected ? 2 : 1,
        ),
      ),
      child: InkWell(
        onTap: onTap,
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 18, vertical: 18),
          child: Row(
            children: [
              Icon(
                paymentMethodIcon(method.code),
                size: 30,
                color: selected ? scheme.primary : scheme.onSurfaceVariant,
              ),
              const SizedBox(width: 16),
              Expanded(
                child: Text(
                  method.name,
                  style: const TextStyle(
                    fontSize: 18,
                    fontWeight: FontWeight.w600,
                  ),
                ),
              ),
              Icon(
                selected ? Icons.radio_button_checked : Icons.radio_button_off,
                color: selected ? scheme.primary : scheme.outline,
              ),
            ],
          ),
        ),
      ),
    );
  }
}

/// Hinweis zur gewählten Methode. Bei EC-Karte groß die Kundennummer, die
/// der Fahrer am EC-Gerät eingeben muss.
class _MethodHint extends StatelessWidget {
  const _MethodHint({required this.method, required this.customerNumber});

  final PaymentMethod method;
  final int customerNumber;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    if (method.code == 'ec_card') {
      return Container(
        padding: const EdgeInsets.all(16),
        decoration: BoxDecoration(
          color: theme.colorScheme.secondaryContainer,
          borderRadius: BorderRadius.circular(16),
        ),
        child: Column(
          children: [
            Text(
              'Kundennummer am EC-Gerät eingeben',
              style: theme.textTheme.titleSmall?.copyWith(
                color: theme.colorScheme.onSecondaryContainer,
              ),
            ),
            const SizedBox(height: 6),
            FittedBox(
              fit: BoxFit.scaleDown,
              child: SelectableText(
                '$customerNumber',
                style: theme.textTheme.displayMedium?.copyWith(
                  fontWeight: FontWeight.w800,
                  letterSpacing: 4,
                  fontFeatures: const [FontFeature.tabularFigures()],
                  color: theme.colorScheme.onSecondaryContainer,
                ),
              ),
            ),
          ],
        ),
      );
    }
    final text = switch (method.code) {
      'cash' => 'Betrag bar entgegennehmen und danach bestätigen.',
      'invoice' =>
        'Der Betrag wird per Rechnung beglichen. Es wird vor Ort '
            'nichts kassiert.',
      _ => 'Zahlung abwickeln und danach bestätigen.',
    };
    return Text(
      text,
      style: theme.textTheme.bodyMedium?.copyWith(
        color: theme.colorScheme.onSurfaceVariant,
      ),
    );
  }
}