import 'dart:async';
import 'dart:convert';

import 'package:commons_core/commons_core.dart';

import '../security/secret_store.dart';

/// A person's saved ("favorite") market offers — other people's listings they
/// bookmarked, Wallapop-style. Keystore-backed (no plaintext at rest) and
/// namespaced by the active identity's [accountScope], like [ProfileStore].
///
/// We keep a *snapshot* of each offer (not just its coordinate) so the Favorites
/// list renders offline, and so a since-withdrawn offer can still be shown as
/// "no longer available" instead of vanishing. The stable key is the offer's
/// addressable coordinate `authorPubkeyHex:id` ([keyOf]).
class SavedOffersStore {
  SavedOffersStore(this._store, {String accountScope = ''})
    : _key = accountScope.isEmpty
          ? 'tane.social.saved_offers'
          : 'tane.social.$accountScope.saved_offers';

  final SecretStore _store;
  final String _key;

  final _changes = StreamController<void>.broadcast();

  /// Emits whenever the saved set changes, so open screens can refresh.
  Stream<void> get changes => _changes.stream;

  /// The stable per-offer key: its NIP-99 addressable coordinate without the
  /// kind (`authorPubkeyHex:id`). Same offer → same key on every device.
  static String keyOf(Offer offer) => '${offer.authorPubkeyHex}:${offer.id}';

  /// Every saved offer, newest first (by save time).
  Future<List<Offer>> list() async {
    final raw = await _store.read(_key);
    if (raw == null || raw.isEmpty) return const [];
    final entries = (jsonDecode(raw) as List)
        .cast<Map<String, dynamic>>()
        .toList()
      ..sort((a, b) => (b['savedAt'] as int).compareTo(a['savedAt'] as int));
    return [for (final e in entries) _decode(e)];
  }

  /// Whether [key] (from [keyOf]) is currently saved.
  Future<bool> isSaved(String key) async =>
      (await _rawList()).any((e) => e['key'] == key);

  /// Saves [offer] (idempotent on its key). Newer snapshot replaces an older one.
  Future<void> save(Offer offer, {required int savedAt}) async {
    final key = keyOf(offer);
    final list = await _rawList()..removeWhere((e) => e['key'] == key);
    list.add({..._encode(offer), 'key': key, 'savedAt': savedAt});
    await _writeRaw(list);
  }

  /// Removes the saved offer with [key] (from [keyOf]); no-op if absent.
  Future<void> remove(String key) async {
    final list = await _rawList()..removeWhere((e) => e['key'] == key);
    await _writeRaw(list);
  }

  /// Toggles [offer]'s saved state; returns the new state (true = now saved).
  Future<bool> toggle(Offer offer, {required int savedAt}) async {
    if (await isSaved(keyOf(offer))) {
      await remove(keyOf(offer));
      return false;
    }
    await save(offer, savedAt: savedAt);
    return true;
  }

  Future<List<Map<String, dynamic>>> _rawList() async {
    final raw = await _store.read(_key);
    if (raw == null || raw.isEmpty) return [];
    return (jsonDecode(raw) as List).cast<Map<String, dynamic>>().toList();
  }

  Future<void> _writeRaw(List<Map<String, dynamic>> list) async {
    await _store.write(_key, jsonEncode(list));
    if (!_changes.isClosed) _changes.add(null);
  }

  Map<String, dynamic> _encode(Offer o) => {
    'id': o.id,
    'author': o.authorPubkeyHex,
    'summary': o.summary,
    'type': o.type.name,
    'status': o.status.name,
    if (o.category != null) 'category': o.category,
    'geohash': o.approxGeohash,
    if (o.radiusKm != null) 'radiusKm': o.radiusKm,
    if (o.priceAmount != null) 'priceAmount': o.priceAmount,
    if (o.priceCurrency != null) 'priceCurrency': o.priceCurrency,
    if (o.exchangeTerms != null) 'exchangeTerms': o.exchangeTerms,
    if (o.imageUrl != null) 'imageUrl': o.imageUrl,
    if (o.expiresAt != null) 'expiresAt': o.expiresAt!.millisecondsSinceEpoch,
    'isOrganic': o.isOrganic,
  };

  Offer _decode(Map<String, dynamic> e) => Offer(
    id: e['id'] as String,
    authorPubkeyHex: e['author'] as String,
    summary: e['summary'] as String,
    type: OfferType.values.byName(e['type'] as String),
    status: OfferLifecycle.values.byName(e['status'] as String? ?? 'active'),
    category: e['category'] as String?,
    approxGeohash: e['geohash'] as String? ?? '',
    radiusKm: e['radiusKm'] as int?,
    priceAmount: e['priceAmount'] as num?,
    priceCurrency: e['priceCurrency'] as String?,
    exchangeTerms: e['exchangeTerms'] as String?,
    imageUrl: e['imageUrl'] as String?,
    expiresAt: e['expiresAt'] == null
        ? null
        : DateTime.fromMillisecondsSinceEpoch(e['expiresAt'] as int),
    isOrganic: e['isOrganic'] as bool? ?? false,
  );

  Future<void> close() async {
    await _changes.close();
  }
}