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

import 'package:commons_core/commons_core.dart';

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

/// A person's saved market searches with their alert bookkeeping — the query
/// and facets they want to be notified about, Wallapop-style. Keystore-backed
/// (no plaintext at rest) and namespaced by the active identity's
/// [accountScope], like [SavedOffersStore].
///
/// Per search we also persist:
/// - [_seenKeysField]: offer coordinates (`authorPubkeyHex:id`) already alerted
///   on, so a relay replaying stored/edited events never re-notifies. Capped at
///   [_seenCap] (oldest dropped) to keep the blob small.
/// - [_newKeysField]: matches the user hasn't looked at yet — the badge source,
///   cleared when they open the search.
class SavedSearchesStore {
  SavedSearchesStore(this._store, {String accountScope = ''})
      : _key = accountScope.isEmpty
            ? 'tane.social.saved_searches'
            : 'tane.social.$accountScope.saved_searches';

  final SecretStore _store;
  final String _key;

  static const _seenCap = 500;
  static const _seenKeysField = 'seenKeys';
  static const _newKeysField = 'newKeys';

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

  /// Emits whenever the stored searches or their alert counts change, so open
  /// screens and badges can refresh.
  Stream<void> get changes => _changes.stream;

  /// The stable per-offer key used for dedup: its addressable coordinate
  /// (`authorPubkeyHex:id`), matching [SavedOffersStore.keyOf].
  static String keyOf(Offer offer) => '${offer.authorPubkeyHex}:${offer.id}';

  /// Every saved search, newest first (by creation time).
  Future<List<SavedSearch>> list() async {
    final entries = await _rawList()
      ..sort((a, b) =>
          ((b['createdAt'] as int?) ?? 0).compareTo((a['createdAt'] as int?) ?? 0));
    return [for (final e in entries) SavedSearch.fromJson(e)];
  }

  /// Whether a search with [id] exists.
  Future<bool> exists(String id) async =>
      (await _rawList()).any((e) => e['id'] == id);

  /// Saves [search] (idempotent on its id). [seedSeenKeys] pre-marks offers the
  /// user has already seen (the current on-screen matches), so they aren't
  /// alerted about listings that were visible when they saved the search.
  Future<void> save(
    SavedSearch search, {
    Iterable<String> seedSeenKeys = const [],
  }) async {
    final list = await _rawList();
    final existing = _find(list, search.id);
    final seen = <String>{
      ...?(existing?[_seenKeysField] as List?)?.cast<String>(),
      ...seedSeenKeys,
    };
    list
      ..removeWhere((e) => e['id'] == search.id)
      ..add({
        ...search.toJson(),
        _seenKeysField: _capped(seen.toList()),
        // Keep any unread matches on re-save (e.g. an edit), else start empty.
        _newKeysField:
            (existing?[_newKeysField] as List?)?.cast<String>() ?? const [],
      });
    await _writeRaw(list);
  }

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

  /// Records that [offerKey] matched search [id]: adds it to both the seen set
  /// (so it never re-alerts) and the unread set (so the badge shows it).
  /// Returns true when this is a fresh match worth notifying about; false when
  /// the key was already seen (a replay/echo) or the search is gone.
  Future<bool> markMatched(String id, String offerKey) async {
    final list = await _rawList();
    final entry = _find(list, id);
    if (entry == null) return false;
    final seen = (entry[_seenKeysField] as List?)?.cast<String>() ?? const [];
    if (seen.contains(offerKey)) return false;
    entry[_seenKeysField] = _capped([...seen, offerKey]);
    final unread = (entry[_newKeysField] as List?)?.cast<String>() ?? const [];
    if (!unread.contains(offerKey)) {
      entry[_newKeysField] = [...unread, offerKey];
    }
    await _writeRaw(list);
    return true;
  }

  /// Clears the unread matches for search [id] (the user opened it).
  Future<void> markViewed(String id) async {
    final list = await _rawList();
    final entry = _find(list, id);
    if (entry == null) return;
    if (((entry[_newKeysField] as List?) ?? const []).isEmpty) return;
    entry[_newKeysField] = const [];
    await _writeRaw(list);
  }

  /// Unread match count for a single search.
  Future<int> newMatchCount(String id) async {
    final entry = _find(await _rawList(), id);
    return ((entry?[_newKeysField] as List?) ?? const []).length;
  }

  /// Total unread matches across every saved search (the app-level badge).
  Future<int> totalNewMatchCount() async {
    var total = 0;
    for (final e in await _rawList()) {
      total += ((e[_newKeysField] as List?) ?? const []).length;
    }
    return total;
  }

  static Map<String, dynamic>? _find(
    List<Map<String, dynamic>> list,
    String id,
  ) {
    for (final e in list) {
      if (e['id'] == id) return e;
    }
    return null;
  }

  /// Keeps only the newest [_seenCap] keys (list is append-ordered, so drop
  /// from the front).
  static List<String> _capped(List<String> keys) => keys.length <= _seenCap
      ? keys
      : keys.sublist(keys.length - _seenCap);

  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>>()
        .map((e) => Map<String, dynamic>.from(e))
        .toList();
  }

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

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