import 'package:flutter/material.dart';

import '../api.dart';
import '../main.dart';

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

  @override
  State<WahlScreen> createState() => _WahlScreenState();
}

class _WahlScreenState extends State<WahlScreen> {
  Future<GuestOverview>? _future;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _future ??= AppScope.of(context).api.guestWahlOverview();
  }

  void _reload() {
    setState(() {
      _future = AppScope.of(context).api.guestWahlOverview();
    });
  }

  @override
  Widget build(BuildContext context) {
    return DefaultTabController(
      length: 2,
      child: Scaffold(
        appBar: AppBar(
          title: const Text('Workshop-Wahl'),
          bottom: const TabBar(tabs: [Tab(text: 'Wünsche'), Tab(text: 'Ergebnis')]),
        ),
        body: TabBarView(
          children: [
            FutureBuilder<GuestOverview>(
              future: _future,
              builder: (context, snap) {
                if (snap.connectionState != ConnectionState.done) {
                  return const Center(child: CircularProgressIndicator());
                }
                if (snap.hasError) {
                  return _ErrorView(message: '${snap.error}', onRetry: _reload);
                }
                final data = snap.data!;
                if (data.wahlen.isEmpty) {
                  return const Center(child: Text('Aktuell ist keine Wahl geöffnet.'));
                }
                return ListView(
                  padding: const EdgeInsets.all(16),
                  children: [
                    Text(data.kcName, style: Theme.of(context).textTheme.titleMedium),
                    const SizedBox(height: 8),
                    for (final w in data.wahlen)
                      _WahlCard(wahl: w, onSubmitted: _reload),
                  ],
                );
              },
            ),
            const _ErgebnisTab(),
          ],
        ),
      ),
    );
  }
}

class _ErgebnisTab extends StatefulWidget {
  const _ErgebnisTab();
  @override
  State<_ErgebnisTab> createState() => _ErgebnisTabState();
}

class _ErgebnisTabState extends State<_ErgebnisTab> {
  Future<List<WahlResult>>? _future;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    _future ??= AppScope.of(context).api.guestWahlResults();
  }

  void _reload() {
    setState(() => _future = AppScope.of(context).api.guestWahlResults());
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<List<WahlResult>>(
      future: _future,
      builder: (context, snap) {
        if (snap.connectionState != ConnectionState.done) {
          return const Center(child: CircularProgressIndicator());
        }
        if (snap.hasError) {
          return _ErrorView(message: '${snap.error}', onRetry: _reload);
        }
        final results = snap.data!;
        if (results.isEmpty) {
          return const Center(child: Text('Noch keine Teilnahme an einer Wahl.'));
        }
        return RefreshIndicator(
          onRefresh: () async => _reload(),
          child: ListView(
            padding: const EdgeInsets.all(16),
            children: [for (final r in results) _ResultCard(result: r)],
          ),
        );
      },
    );
  }
}

class _ResultCard extends StatelessWidget {
  const _ResultCard({required this.result});
  final WahlResult result;

  @override
  Widget build(BuildContext context) {
    final (label, color, detail) = switch (result.status) {
      WahlResultStatus.assigned => (
          result.workshopName ?? 'Zugeteilt',
          Colors.green,
          result.isForced
              ? 'Fest zugeteilt (Leitungsteam)'
              : 'Wunsch ${result.wunschRang ?? '?'}',
        ),
      WahlResultStatus.unassigned => (
          'Kein Platz frei',
          Theme.of(context).colorScheme.error,
          'Bitte beim Leitungsteam melden.',
        ),
      WahlResultStatus.pending => (
          'Noch nicht zugeteilt',
          Theme.of(context).colorScheme.outline,
          'Die Zuteilung läuft noch.',
        ),
    };
    return Card(
      margin: const EdgeInsets.only(bottom: 12),
      child: ListTile(
        leading: Icon(Icons.emoji_events, color: color),
        title: Text('${result.wahlName}  ·  ${result.datumsSchluessel} Teil ${result.teil}',
            style: Theme.of(context).textTheme.bodySmall),
        subtitle: Text(label, style: Theme.of(context).textTheme.titleMedium),
        trailing: Text(detail, textAlign: TextAlign.end),
      ),
    );
  }
}

class _WahlCard extends StatefulWidget {
  const _WahlCard({required this.wahl, required this.onSubmitted});
  final Wahl wahl;
  final VoidCallback onSubmitted;

  @override
  State<_WahlCard> createState() => _WahlCardState();
}

class _WahlCardState extends State<_WahlCard> {
  late final List<String> _picked = [...?widget.wahl.meinePrioritaeten];
  bool _busy = false;
  String? _error;
  bool _done = false;

  static const _maxPicks = 3;

  void _toggle(String workshopId) {
    setState(() {
      if (_picked.contains(workshopId)) {
        _picked.remove(workshopId);
      } else if (_picked.length < _maxPicks) {
        _picked.add(workshopId);
      }
      _done = false;
    });
  }

  Future<void> _submit() async {
    setState(() {
      _busy = true;
      _error = null;
    });
    try {
      await AppScope.of(context).api.submitPrioritaeten(widget.wahl.id, _picked);
      setState(() => _done = true);
      widget.onSubmitted();
    } on ApiException catch (e) {
      setState(() => _error = e.message);
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    final w = widget.wahl;
    return Card(
      margin: const EdgeInsets.only(bottom: 16),
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(w.name, style: Theme.of(context).textTheme.titleLarge),
            Text('${w.datumsSchluessel} · Teil ${w.teil}',
                style: Theme.of(context).textTheme.bodySmall),
            const SizedBox(height: 4),
            Text(
              'Tippe deine Wünsche in Reihenfolge an (max. $_maxPicks). '
              'Die Zahl zeigt den Rang.',
              style: Theme.of(context).textTheme.bodySmall,
            ),
            const SizedBox(height: 8),
            for (final ws in w.workshops)
              _WorkshopRow(
                workshop: ws,
                rank: _picked.indexOf(ws.id),
                enabled: !_busy,
                onTap: () => _toggle(ws.id),
              ),
            const SizedBox(height: 12),
            if (_error != null) ...[
              Text(_error!, style: TextStyle(color: Theme.of(context).colorScheme.error)),
              const SizedBox(height: 8),
            ],
            Row(
              children: [
                FilledButton(
                  onPressed: (_busy || _picked.isEmpty) ? null : _submit,
                  child: _busy
                      ? const SizedBox(
                          height: 18, width: 18, child: CircularProgressIndicator(strokeWidth: 2))
                      : const Text('Wünsche absenden'),
                ),
                const SizedBox(width: 12),
                if (_done)
                  Row(
                    children: const [
                      Icon(Icons.check_circle, color: Colors.green, size: 20),
                      SizedBox(width: 4),
                      Text('Gespeichert'),
                    ],
                  ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

class _WorkshopRow extends StatelessWidget {
  const _WorkshopRow({
    required this.workshop,
    required this.rank,
    required this.enabled,
    required this.onTap,
  });
  final Workshop workshop;
  final int rank;
  final bool enabled;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final selected = rank >= 0;
    return ListTile(
      dense: true,
      enabled: enabled,
      onTap: onTap,
      leading: CircleAvatar(
        radius: 14,
        backgroundColor: selected
            ? Theme.of(context).colorScheme.primary
            : Theme.of(context).colorScheme.surfaceContainerHighest,
        child: Text(
          selected ? '${rank + 1}' : '',
          style: TextStyle(
            fontSize: 13,
            color: selected ? Theme.of(context).colorScheme.onPrimary : null,
          ),
        ),
      ),
      title: Text(workshop.name),
      subtitle: Text('Kapazität ${workshop.kapazitaet}'),
      trailing: Icon(selected ? Icons.check_box : Icons.check_box_outline_blank),
    );
  }
}

class _ErrorView extends StatelessWidget {
  const _ErrorView({required this.message, required this.onRetry});
  final String message;
  final VoidCallback onRetry;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(24),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Text(message, textAlign: TextAlign.center),
            const SizedBox(height: 12),
            OutlinedButton(onPressed: onRetry, child: const Text('Erneut versuchen')),
          ],
        ),
      ),
    );
  }
}