import 'dart:async';

import 'package:commons_core/commons_core.dart';
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

import '../i18n/strings.g.dart';
import '../services/saved_offers_store.dart';
import '../services/social_connection.dart';
import 'market_widgets.dart';
import 'theme.dart';

/// The Wallapop-style "Favorites": offers from other people the user saved.
/// Shows the saved snapshots offline-first; when a relay is reachable it checks
/// which ones are still published and flags the rest as no longer available
/// (they may have been withdrawn or expired). Tapping opens the offer detail.
class FavoritesScreen extends StatefulWidget {
  const FavoritesScreen({
    required this.savedOffers,
    this.connection,
    super.key,
  });

  final SavedOffersStore savedOffers;

  /// The shared relay connection, used to check whether saved offers still
  /// exist. Null (tests / no social layer) → no check, snapshots shown as-is.
  final SocialConnection? connection;

  @override
  State<FavoritesScreen> createState() => _FavoritesScreenState();
}

class _FavoritesScreenState extends State<FavoritesScreen> {
  List<Offer>? _offers;
  var _liveKeys = <String>{};
  var _checked = false;
  StreamSubscription<void>? _changesSub;

  @override
  void initState() {
    super.initState();
    _changesSub = widget.savedOffers.changes.listen((_) => _load());
    _load();
  }

  @override
  void dispose() {
    _changesSub?.cancel();
    super.dispose();
  }

  Future<void> _load() async {
    final offers = await widget.savedOffers.list();
    if (!mounted) return;
    setState(() => _offers = offers);
    unawaited(_check(offers));
  }

  /// Asks the relay which saved offers are still out there. Offline (no session)
  /// leaves [_checked] false, so nothing is wrongly flagged as gone.
  Future<void> _check(List<Offer> offers) async {
    final connection = widget.connection;
    if (connection == null || offers.isEmpty) return;
    final session = await connection.session();
    if (session == null || !mounted) return;

    final live = <String>{};
    final geohashes = {
      for (final o in offers)
        if (o.approxGeohash.isNotEmpty) o.approxGeohash,
    };
    final subs = <StreamSubscription<Offer>>[];
    for (final geohash in geohashes) {
      subs.add(
        session.offers
            .discover(DiscoveryQuery(geohashPrefix: geohash))
            .listen((o) => live.add(SavedOffersStore.keyOf(o)), onError: (_) {}),
      );
    }
    // The discover streams stay open for live offers and never signal "done";
    // give them a beat to deliver what's stored, then take stock.
    await Future<void>.delayed(const Duration(seconds: 5));
    for (final s in subs) {
      unawaited(s.cancel());
    }
    if (!mounted) return;
    setState(() {
      _liveKeys = live;
      _checked = true;
    });
  }

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    final offers = _offers;
    return Scaffold(
      appBar: AppBar(title: Text(t.favorites.title)),
      body: offers == null
          ? const Center(child: CircularProgressIndicator())
          : offers.isEmpty
          ? _Empty(text: t.favorites.empty)
          : ListView.separated(
              padding: const EdgeInsets.all(12),
              itemCount: offers.length,
              separatorBuilder: (_, _) => const SizedBox(height: 10),
              itemBuilder: (context, i) {
                final offer = offers[i];
                final key = SavedOffersStore.keyOf(offer);
                // Only call something gone once a check actually ran and didn't
                // see it — never while offline (checked == false).
                final gone = _checked && !_liveKeys.contains(key);
                return _FavoriteCard(
                  offer: offer,
                  unavailable: gone,
                  onOpen: () => context.push('/market/offer', extra: offer),
                  onRemove: () => widget.savedOffers.remove(key),
                );
              },
            ),
    );
  }
}

class _FavoriteCard extends StatelessWidget {
  const _FavoriteCard({
    required this.offer,
    required this.unavailable,
    required this.onOpen,
    required this.onRemove,
  });

  final Offer offer;
  final bool unavailable;
  final VoidCallback onOpen;
  final VoidCallback onRemove;

  @override
  Widget build(BuildContext context) {
    final t = context.t;
    final radius = BorderRadius.circular(14);
    return Material(
      color: Colors.white,
      borderRadius: radius,
      child: InkWell(
        key: Key('favorites.offer.${offer.authorPubkeyHex}.${offer.id}'),
        onTap: onOpen,
        borderRadius: radius,
        child: Container(
          decoration: BoxDecoration(
            borderRadius: radius,
            border: Border.all(color: seedOutline),
          ),
          padding: const EdgeInsets.all(16),
          child: Opacity(
            opacity: unavailable ? 0.55 : 1,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Row(
                  children: [
                    if (offer.imageUrl != null) ...[
                      OfferThumbnail(
                        url: offer.imageUrl!,
                        semanticLabel: t.market.photo,
                      ),
                      const SizedBox(width: 12),
                    ],
                    Expanded(
                      child: Text(
                        offer.summary,
                        style: const TextStyle(
                          fontSize: 17,
                          fontWeight: FontWeight.w500,
                          color: seedOnSurface,
                        ),
                      ),
                    ),
                    IconButton(
                      key: Key('favorites.remove.${offer.authorPubkeyHex}'
                          '.${offer.id}'),
                      icon: const Icon(Icons.favorite, color: seedGreen),
                      tooltip: t.favorites.remove,
                      onPressed: onRemove,
                    ),
                  ],
                ),
                const SizedBox(height: 4),
                Row(
                  children: [
                    if (unavailable)
                      Row(
                        children: [
                          const Icon(Icons.cloud_off,
                              size: 15, color: seedMuted),
                          const SizedBox(width: 4),
                          Text(
                            t.favorites.unavailable,
                            style:
                                const TextStyle(color: seedMuted, fontSize: 13),
                          ),
                        ],
                      )
                    else
                      OfferTypeChip(label: offerTypeLabel(t, offer.type)),
                    const Spacer(),
                    if (offer.type == OfferType.sale && offer.priceAmount != null)
                      Text(
                        '${offer.priceAmount} ${offer.priceCurrency ?? ''}'
                            .trim(),
                        style: const TextStyle(
                          color: seedOnSurface,
                          fontWeight: FontWeight.w600,
                        ),
                      ),
                  ],
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class _Empty extends StatelessWidget {
  const _Empty({required this.text});

  final String text;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(24),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(
              Icons.favorite_border,
              size: 64,
              color: seedGreen.withValues(alpha: 0.5),
            ),
            const SizedBox(height: 16),
            Text(
              text,
              textAlign: TextAlign.center,
              style: Theme.of(context).textTheme.bodyLarge,
            ),
          ],
        ),
      ),
    );
  }
}